Ecocem Use of GGBS Concrete Mixes

UCD School of Architecture, Landscape

and Civil Engineering

Use of GGBS Concrete Mixes for

Aggressive Infrastructural Applications

ENTERPRISE IRELAND ECOCEM IRELAND

INNOVATION PARTNERSHIP PROGRAMME

PROJECT CODE IP/2008/0540

Executive summary

The case for research into the deterioration associated with water and wastewater

infrastructure has been clearly made. For example in the US alone, the Congressional Budget

Office has estimated that annual investments of up to $20 billion and $21 billion is required

to provide adequate infrastructure for drinking water and wastewater respectively. It is also

estimated that the annual operation and maintenance costs associated with drinking water and

wastewater infrastructure to be in excess of $31 billion and $25 billion respectively. In

Ireland, the Government have previously announced that under the Water Services

Investment Plan, €5.8 billion will be spent on this sector. As such, this represents a

potentially lucrative market that exists both in Ireland and internationally.

Research was conducted into the performance of concrete samples manufactured using a

range of binder combinations which were subjected to aggressive environments selected to

represent the most extreme of conditions they will encounter in service. These included attack

from sulfates and from biogenic sulfuric acid. The test results found that:

• In sodium sulfate expansion tests, traditional CEM I cements performed significantly

poorer than all other binder combinations. Samples manufactured using the newer

CEM II/A-L binders displayed increased resistance to sulfate attack but still failed to

meet standard performance criteria.

• The samples with the highest resistance to sulfate attack were those that contained

50% or 70% GGSB as a cement replacement level, which displayed very low

expansion levels. This also included superior resistance levels than that obtained using

sulfate-resisting Portland cement.

• In all cases deterioration was primarily due to bulging, spalling and warping, most

likely as a result of the formation of gypsum.

• When subjected to a 1% sulfuric acid solution (pH 1.3), significant surface corrosion

was observed for all binder combinations. Very little distinction was observed

between the various binder combinations.

• The main deterioration mechanism consisted of the formation of gypsum on the

external surfaces of the concrete specimens. This was followed by surface

delamination, some spalling. In the long term a widespread lack of cohesion leads to a

failure mechanism that spreads directly to the core.

The results of this investigation have clearly outlined the cause of concrete deterioration in

wastewater treatment systems and distinguished between degradation due to sulfate attack

and that due to a sulfuric acid attack in this environment. There is a need to train concrete

specifiers in understanding the harsh conditions that these structures will encounter in

service. However for this to be fully realised, the range of aggressive environments

associated with wastewater applications needs quantification.

Dr Ciaran McNally, Project Manager

TABLE OF CONTENTS

1 INTRODUCTION .................................................................................................................... 1

2 LITERATURE REVIEW ......................................................................................................... 3

3 EXPERIMENTAL PROGRAMME: MATERIALS AND METHODS ................................. 4

3.1 Experimental Overview .................................................................................................... 4

3.2 Materials and methods ...................................................................................................... 5

3.2.1 Sodium sulfate expansion tests .................................................................................. 5

3.2.2 Sulfuric acid tests ....................................................................................................... 7

3.3 Ultrasonic Tests .............................................................................................................. 10

3.3.1 Review of current research ....................................................................................... 10

3.3.2 Experimental setup ................................................................................................... 11

3.4 Permeability tests ............................................................................................................ 13

4 EXPERIMENTAL PROGRAMME: RESULTS ................................................................... 14

4.1 Overview ........................................................................................................................ 14

4.2 Sodium sulfate expansion results ................................................................................... 14

4.3 Discussion of sodium sulfate expansion results ............................................................. 23

4.3.1 Dilution effect .......................................................................................................... 23

4.3.2 Permeability and porosity ......................................................................................... 24

4.3.3 The Influence of C3A ............................................................................................... 25

4.3.4 Influence of C3S and C2S ......................................................................................... 27

4.3.5 Sulfate resisting capabilities of CEM II/A-L and GGBS concretes ......................... 27

4.4 Sulfuric acid test results .................................................................................................. 29

4.4.1 Mass loss results ....................................................................................................... 29

4.4.2 Discussion of deterioration mechanism ................................................................... 34

4.4.3 Cube strength tests ................................................................................................... 36

4.4.4 Sulfuric acid expansion tests .................................................................................... 37

4.5 Ultrasonic results ............................................................................................................ 38

4.5.1 Stiffness loss in due to sulfuric acid testing ............................................................. 38

4.5.2 Stiffness loss in concrete exposed to a 1% sulfuric acid solution ............................ 41

4.5.3 Discussion of ultrasonic results ................................................................................ 46

4.5.4 Microstructural Effects ............................................................................................. 46

4.5.5 Chemical effects ....................................................................................................... 48

4.6 Permeability, absorption and sorptivity results .............................................................. 49

5 DISCUSSION ........................................................................................................................ 51

5.1 Sulfate experimental programme.................................................................................... 51

5.2 Sulfuric acid programme ................................................................................................ 52

5.3 Ultrasonic analysis .......................................................................................................... 54

6 CONCLUSIONS .................................................................................................................... 56

6.1 Sodium sulfate tests ........................................................................................................ 56

6.2 Sulfuric acid tests............................................................................................................ 57

6.3 Summary ......................................................................................................................... 58

1

1 INTRODUCTION

The deterioration of wastewater infrastructure has long been a cause for concern but the issues

surrounding the problem remained unknown for many years. Traditionally designed to resist high

levels of sulfate attack, wastewater treatment systems are subjected to a considerably more

aggressive form of deterioration – biogenic sulfuric acid corrosion. To this day the true

mechanisms of attack have yet to be fully grasped by concrete specifiers and this is evident in the

poor state of infrastructure used in this environment. There is clearly a need to distinguish

between the two forms of attack and the research conducted in this investigation shows that both

the nature and severity of attack is drastically different. Existing methods aimed at counteracting

the corrosive forces focus on remedial work, periodic maintenance and replacement of defective

components. This is clearly not a cost effective practice especially considering that this form of

attack can manifest itself within a relatively short period of time (under ten years).

In examining current European standards one discovers it is not necessarily the fault of the

specifier that integrity of wastewater infrastructure is being compromised at such an early age,

but rather a combination of a lack of understanding of the true mechanisms at work (owing to

largely disjointed research efforts) and a concrete standard that does not adequately distinguish

between the effects of sulfate and sulfuric acid attack. Further research reveals that the current

ability to model sulfate degradation is lacking in both accuracy and reliability meaning adopting

the recommendations of such work would be an unwise course of action. Much of this

uncertainty is reflected by the very complex nature of sulfate attack, and to an extent sulfuric acid

attack. Both mechanisms require an accelerated experimental analysis to monitor their destructive

effects in a reasonable timeframe but by doing so this in turn modifies the nature and severity of

the attack.

In what would appear to be a somewhat Catch 22 scenario, existing recommendations for

these aggressive environments resort to limiting the exposure of concrete to such environments or

increasing cement content while lowering the w/c ratio without truly examining the mechanisms

at work. The need to affect a change in such practice has become more important with the

increased use of secondary cementitious materials in modern concrete practice. The effect of such

additions often modify the chemical composition of a hydrated cement paste making some more

2

vulnerable than others to aggressive chemical environments. Simply referring to these

constituents as “cementitious materials” may no longer be adequate terminology.

Taking all of this into consideration, it is clear that the design of wastewater infrastructure

is both imprecise and most likely inaccurate yet it is through the standards that change must come

in order for a greater understanding to be achieved. Using guidelines such as increasing the

cement content cannot justifiably claim to prevent the occurrence of complex corrosion

mechanisms like those of sulfate, sulfuric acid or biogenic sulfuric acid attack. It would appear

that a more complex and precise means of assessing concrete durability for long term exposures

must be thought of. The challenge remains then to transform such a method into a usable tool for

concrete specification.

Existing research efforts on wastewater infrastructure tend to focus on either the cause or

effect of the corrosion phenomenon while paying little attention to forming a solution to the

problem. On the other hand, those examining possible solutions to sulfate or acidic corrosion fail

to understand the biological aspects sometimes at work and the variability of the bacterial attack.

These disjointed efforts remain the primary hurdle in establishing an authoritative direction in

which to lead future research and it is the goal of this investigation to adequately contrast the

separate corrosive phenomenon and to provide the guidance required to affect such a path.

3

2 LITERATURE REVIEW

A thorough review of the literature was conducted and a review paper was written entitled

“Biochemical Attack on Concrete in Wastewater Applications: a State of the Art Review”. This

paper was published in the peer-reviewed journal Cement and Concrete Composites and the full

citation for the paper is: O'Connell, M, McNally, C & Richardson, MG (2010) 'Biochemical

attack on concrete in wastewater applications: a state of the art review'. Cement and Concrete

Composites, 32 (7):479-485. The paper is attached as an Appendix to this report.

This study found that international research to date has focussed on three distinct topics in the

study of sulfate/sulfuric acid effects on concrete. These are:

• Studies of the biological processes behind the corrosion of wastewater infrastructure, with

particular reference to the role of sulfate-reducing and sulfur-oxidising bacteria.

• Studies of the chemical effects of sulfates and sulfuric acid on concrete mixes

• Laboratory-based research methodologies, especially those incorporating the biological

effect on concrete.

It was concluded that chemical tests alone do not fully represent the microbial effects on

concrete, although they may help in assessing the types of damage that can occur. Some

researchers have carried out full-scale laboratory analysis, but it is worth noting that the

equipment necessary to adequately mimic in-situ conditions is invariably complicated,

cumbersome and custom built. The realisation of resources required to undertake such research

continues to be an obstacle to addressing this topic. The use of such complex research apparatus

in routine performance-based specification is impractical.

Although there exists significant quantities of data on the topics of sulfate, sulfuric acid and

biogenic corrosion of concrete, little has been achieved in the way of formulating an accepted

mathematical model of deterioration that incorporates agreed parameters of significance. This

represents a significant knowledge gap and acts as a technical barrier towards using material

design as a means of controlling corrosion due to biochemical attack. This continues to inhibit the

design of durable concrete wastewater infrastructure and has significant implications for public

expenditure in this area. The need to consider the interaction of biological and chemical processes

may hold the key to achieving greater progress and allow practitioners to use concrete mix design

as a means of delivering intended service lives.

4

3 EXPERIMENTAL PROGRAMME: MATERIALS AND METHODS

3.1 Experimental Overview

The aim of this investigation is to examine the behaviour of concrete and mortar in aggressive

chemical environments containing sulfate and sulfuric acid with a view to recommending a

specification that can be used to optimise the expected service life in such harsh conditions.

Specimens containing cement replacement levels of 0 %, 50% and 70% with ground granulated

blast-furnace slag (GGBS) were tested along with a sulfate resisting Portland cement mix. The

materials used for this investigation were locally sourced and consisted of sand, CEM II-A/L

limestone cement, CEM I ordinary Portland cement, sulfate resisting Portland cement, granulated

ground blast-furnace slag (GGBS) and coarse limestone aggregate graded 10mm and 20mm

(Table 3.1). The test programme comprised monitoring performance through:

• Sodium sulfate expansion tests

• Sulfuric acid tests

• Ultrasonic tests

Table 3.1 – Experimental materials

Material Sulfuric Acid Tests Sodium Sulfate Tests

Sand Hanlon’s, Co. Kildare CEN-Normensand

(DIN EN 196-1)

Cement CEM I, CEM II/A-L, SRPC CEM I, CEM II/A-L, SRPC

Cement replacement GGBS

(0%, 50% & 70%)

GGBS

(0%, 50% & 70%)

Coarse Aggregate 10mm & 20mm

Belgard limestone

None

Water Tap water Tap water

5

3.2 Materials and methods

3.2.1 Sodium sulfate expansion tests

A modified ASTM C1012 procedure was used to test the mortar prisms for change of length

when exposed to a sulfate solution. The modification consisted of recording comparator

measurements on a fixed 28-day interval for the duration of the analysis. Mortar prisms of

dimensions 285mm x 25mm x 25mm (Figure 3.1) were prepared through use of the standard mix

in EN196-1 for cement conformity testing. Each mix contained 450g of binder, 1350g of sand

(CEN-Normensand DIN EN 196-1) and 225g of water and produced four prisms. The freshly

cast specimens were placed in a moist air cabinet at 20˚C and demoulded after twenty-four hours.

Following demoulding they were immersed in a water bath at 20˚C and allowed to cure until an

age of twenty-eight days.

Table 3.2 – Mix designations

Mix Designation Cement Type % GGBS

MA CEM II/A-L 0

MB CEM II/A-L 50

MC CEM II/A-L 70

MD CEM I 0

ME CEM I 70

SR SRPC 0

The standard exposure solution used in this test method contains 50g of sodium sulfate

(Na2SO4) per litre of distilled water. Each solution was prepared with 4.5l of distilled water and

mechanically stirred until fully dissolved. The solution was then topped up with distilled water

until a volume of 5l was achieved. It was then placed into a standard domestic polyethylene

container ensuring the quantity was sufficient to cover the prisms by a minimum of 5mm.

6

Figure 3.1 – Example of the ASTM C1012 standard mortar prisms

The prisms were stored for a period in excess of one year and the solution was refreshed on

a monthly basis. This consisted of the disposal of the spent solution, the storage tank rinsed with

water and a fresh sodium sulfate solution prepared as previously detailed. Comparator readings

were taken every four weeks. The readings consisted of taking an initial reference measurement

for each prism and a standard reference invar bar prior to immersion in the sodium sulfate

solution. The change in length of the prism is recorded with reference to the initial reading and is

then calculated according to:

∆� = �� × 100 Eqn. 1

ΔL = change of length at age ‘x’ (%)

Lx = comparator reading of specimen at age ‘x’ – reference bar comparator reading at age ‘x’

Li = initial comparator reading of specimen – reference bar comparator reading at the same time

Lg = nominal gauge length or 250mm as applicable

The percentage change of length of each prism was expressed to an accuracy of 0.001%

and the average of the four test specimens was recorded. A photographic record of the prisms was

7

carried out at eight week intervals to document any change in the physical appearance of the

specimens.

Figure 3.2 – Comparator reader with reference bar

3.2.2 Sulfuric acid tests

The aim of the experimental programme was to assess the performance of six different concrete

mixes exposed to environmental conditions similar to those found in wastewater treatment plants.

The cubes were immersed in a 1% sulfuric acid solution for six months and monitored for mass

loss, expansion, visual appearance and compressive strength. Three of the mixes consisted of

CEM II-A/L limestone cement with 0%, 50% and 70% additions of GGBS as a cement

replacement, two contained CEM I Portland cement with 0% and 70% GGBS while the final mix

was a standard sulfate resisting SRPC mix. The performance of GGBS in an acidic environment

was of particular interest while the performance of limestone cement remains largely

undocumented in this type of aggressive environment.

8

Fourteen concrete cubes measuring 100mm were cast for each mix with varying

percentages of GGBS as a cement replacement indicated in Table 3.2. The water / binder ratio

was specified at 0.45 and binder content at 360kg/m3 to represent the limitations permitted under

exposure class XA3 (>3000mg/l and ≤6000 mg/l SO42-; pH ≤4.5 and >4) as detailed in IS/EN

206-1. Simultaneously, four prisms measuring 250mm x 75mm x 75mm were also cast with each

of the different mixes. The mix proportions for each set of cubes are outlined in Table 3.3.

Table 3.3 – Concrete mix quantities for sulfuric acid tests

Quantities (kg/m3)

Mix Type Cement GGBS C20

aggregate

C10

aggregate

Sand Water F/(F + C) Volume

(m3)

MA CEM II/A-L 360 0 810 405 685 162 0.361 0.985

MB CEM II/A-L 180 180 805 400 680 162 0.361 0.984

MC CEM II/A-L 108 252 805 400 680 162 0.361 0.986

MD CEM I 360 0 810 405 685 162 0.361 0.985

ME CEM I 108 252 805 400 680 162 0.361 0.986

SR SRPC 360 0 810 405 685 162 0.361 0.985

Notes:

F = Fine aggregate; C = Coarse aggregate

Volume = Volume fraction of cube space occupied by solid matter

SRPC = Sulfate resisting Portland cement

All of the cubes were stored in a curing tank at 20˚C for twenty-eight days following which

the strength of cubes 1 and 2 for each mix was tested under compression until failure. The

remaining twelve cubes were now divided into two sets of six split between continued storage in

the curing tank and immersion in a 1% sulfuric acid solution at pH≈1.5 for up to 168 days. The

dimension of each cube was also recorded prior to commencing the analysis. Table 3.4 shows the

experimental schedule adopted for the test programme. The samples were brushed with a wire

brush every seven days under running water which resulted in a milky-white runoff. Brushing

was ceased when the runoff colour reverted to clear water. All cubes were weighed every seven

9

days for the first month and every twenty-eight days thereafter to record any mass loss or mass

gain. For those stored in the sulfuric acid solution loosely adhering corrosion products were

brushed away prior to recording mass.

Table 3.4 – Storage and test conditions adopted for the brushed programme

Cube No. Storage Condition Mass Readings Compression Test

1, 2 28 days curing water @20C

ONLY

7, 14, 21 & 28 days After 28 days curing water @20C

3, 4 28 days storage water @20C 7, 14, 21, 28 days, then

every 28 days

After 28 days storage water @20C

9, 12 28 days storage acid @20C 7, 14, 21, 28 days, then

every 28 days

After 28 days storage acid @20C

6, 7 56 days storage water @20C 7, 14, 21, 28 days, then

every 28 days

After 56 days storage water @20C


every 28 days

After 56 days storage acid @ 20C

5, 8 168 days storage water@20C 7, 14, 21, 28 days, then

every 28 days

After 168 days storage water@20C


every 28 days

After 168 days storage acid @20C

The sulfuric acid solution for all experimental schedules was maintained at a pH of

approximately 1.5 by titrating the solution with a more concentrated sulfuric acid to keep the pH

within a margin of ± 0.3. The solution was refreshed once a month to avoid prolonged

contamination associated with the corrosion products of degraded concrete.

A second set of mass loss experiments was undertaken over a twelve-month period

exploring the effect that brushing the specimens, to remove loosely adhering corrosion particles,

has on the attack rate. To this end, a further twelve specimens were cast (two for each respective

mix) and their mass recorded every seven days for the first twenty-eight days and again every

twenty-eight days thereafter until one hundred and sixty eight days exposure was achieved. The

10

cube strengths were also determined for each of the samples after one hundred and sixty eight

days. The technique in the first programme has already been outlined while the second technique

involved no weekly brushing. The specimens were briefly held under running water once a

month, however, before being immersed in a fresh solution of sulfuric acid. The principle behind

each brushing technique was to not only assess the behaviour in two extreme abrasion conditions

for both stagnant and flowing water but also to attempt to mimic the severity of the bacterial acid

attack.

Finally, a parallel experimental regime was carried out to investigate the change of length

of the concrete prisms exposed to the same sulfuric acid solution while adopting an identical

weighing and weekly brushing technique as in Table 3.4. For this, following twenty-eight days

curing, two prisms from each mix were immersed in the sulfuric acid solution while a further two

remained stored in water. An initial reading for each prism was performed prior to immersion

with a standard reference invar bar and subsequent readings taken at twenty-eight day intervals.

The technique and calculations were performed according to those outlined for the sodium sulfate

expansion tests.

Table 3.5 – Test conditions for prisms exposed to 1% sulfuric acid

Prism

No.

Storage Condition Mass Readings Comparator Readings

1,2 168 days storage water

@20C

7, 14, 21, 28 days, then every 28

days

Every 28 days following

curing

3,4 168 days storage acid @20C 7, 14, 21, 28 days, then every 28

days

Every 28 days following

curing

Note: All prisms adopted an identical curing regime of 28 days in water at 20C following which they were exposed

to the storage condition outlined above

3.3 Ultrasonic Tests

3.3.1 Review of current research

Ultrasonic non-destructive testing of concrete possesses a clear time and resources advantage

over traditional methods but often depends on careful interpretation of the results. In the context

11

of promoting high levels of cement replacement materials, the advantages and disadvantages

should be acknowledged. While high replacement levels will have inherent benefits such as a

denser microstructure or the ability to reduce the carbon footprint of a building, they also have

some drawbacks, the most prominent of which is slower initial gain of strength. The development

of a reliable ultrasonic technique to monitor the development of stiffness in early age concrete

would allow us to work with this material property. This was the basis of a research paper that

was presented at a Geophysics conference in Dublin in 2009. This paper described how a method

was developed at UCD that would allow us to use ultrasonic testing to detect the rapidly

occurring changes in the modulus of early age concrete. The full citation for this paper is:

O'Connell, M, McNally, C, Donohue, S, Bonal, J & Richardson, MG (2009) Assessment of

ultrasonic signals to determine the early age properties of concretes incorporating secondary

cementitious materials. In: Proceedings of the 15th European Meeting of Environmental and

Engineering Geophysics, Dublin, 7- 9 September. A copy of the paper is included in Appendix B

of this report.

3.3.2 Experimental setup

The benefit of this work is that while a proven ultrasonic analysis technique can be used to chart

stiffness development in hydrating concrete, it may also be used in monitoring stiffness loss in

concrete subjected to a corrosive environment. During a chemical attack concrete undergoes a

significant alteration of its internal microstructure leading to a loss of strength and ultimately

failure. Often the effects of a sulfate attack, for instance, can only be realised when the

phenomenon has reached a substantial stage of progression. Ultrasonic analysis has the potential

to detect degradation at an early stage and its benefits could be exploited in the monitoring of

critical transport and water infrastructure whether it bridge foundations exposed to aggressive

ground sulfate levels or biogenic sulfuric acid corrosion in wastewater treatment systems. The

ultrasonic investigation of each of the cube specimens required S-wave (transverse shear waves)

and P-wave (longitudinal waves) ultrasonic readings to be taken every twenty-eight days

following immersion in acid. This was maintained for one hundred and sixty eight days. Square-

shaped plastic caps measuring 50mm were attached to two sides of the cubes subjected to

ultrasonic testing and the edges sealed with a mastic glue. This ensured a region protected from

exposure to acid / corrosion on which to place the ultrasonic transducers and obtain a reading.

12

Two sets of transducers were used for this purpose in conjunction with a square wave pulser-

receiver in ‘through-transmission’ mode (Figure 3.3). The S-wave transducers had a frequency of

100 kHz, the P-wave transducers 50 kHz.

Figure 3.3 – Ultrasonic testing equipment (L-R): Laptop, digital oscilliscope, signal generator,

100mm cube with ultrasonic transducers and ultrasonic couplant

For both S-wave and P-wave measurements each transducer was coupled directly opposite

the other using a shear wave couplant gel as this was found to give excellent acoustic properties

for both wave forms. It was essential to ensure a good connection between the couplant and the

concrete as this was found to affect the amplitude of the signal. A 100V amplitude pulse was

emitted into the specimen and the signal allowed to settle. The signals were recorded using a

digital oscilloscope connected to a laptop computer and the results analysed with a Python shear

wave detector algorithm to aid in the detection of the first arrival point (Bonal et al., 2010). An

identical procedure was applied to the specimens used to investigate the effects of brushing with

regular measurements taken at twenty-eight day intervals.

13

3.4 Permeability tests

A series of air permeability, water permeability and water sorption tests were carried out on two

samples each of the six concrete mixes using the Autoclam permeability system (Figure 3.4). A

base ring is attached to the sample and affixed to the apparatus rendering it air/water tight. The

apparatus operates on the following principle: for air permeability, the pressure inside the

apparatus is increased slightly to 0.5 bar and the decay of it is monitored every minute from 0.5

bar for 15 minutes or until the pressure has diminished to zero. A plot of the natural logarithm of

pressure against time (mins) is linear. The air permeability index is taken as the slope of the

linear regression curve between 5 and 15 minutes. For water permeability, water is introduced to

the apparatus’ test area and the pressure is increased to 0.5 bar where it is maintained for the

duration of the test. The quantity of water flowing through the concrete is measured and a straight

line is plotted of the former against the square root of time between the 5th and 15th minute. A

similar regime is implied for the water sorption test however the test pressure is reduced to 0.02

bar and kept constant for the test duration.

Figure 3.4 – Autoclam permeability system with controller on the left and the unit (in blue) on

top of the specimen

14

4 EXPERIMENTAL PROGRAMME: RESULTS

4.1 Overview

This section presents the results of the experimental data obtained for the sodium sulfate

expansion tests, sulfuric acid tests and the ultrasonic analysis testing programme. The percentage

expansions were recorded in the sodium sulfate testing programme in conjunction with a detailed

visual description of the test specimens. A variety of observations are discussed, compared and

contrasted with reference to each of the mixes and an analysis carried out to ascertain the

contributing factors towards their performances. The sulfuric acid tests employed a similar visual

recording and discussion methodology in addition to other parameters being examined including

mass loss, cube strengths and expansion. The ultrasonic testing programme is applied to monitor

the loss in stiffness following exposure to a 1% sulfuric acid solution over a six month period.

The results are compiled and discussed with reference to each mix and their relevant chemical

and physical performance factors.

4.2 Sodium sulfate expansion results

The sulfate expansion tests were carried out as detailed in section 3.2.1 where the solution was

refreshed on a twenty-eight day cycle, maintained at room temperature and the pH of the system

was uncontrolled. Figure 4.1 shows the results of the test program as measured in percentage

expansion according to Eqn. 1. The average

expansion of four prisms was used to obtain the data points in Figure 4.1.

Expansions were obtained for a twelve month period for all six mixes while subsequent

measurements were carried out for some. Early exposure (up to 84 days) for specimens MA, MB,

MC, ME and SR showed an identical trend of expansion registering little movement. MD

however, is already showing greater expansion in comparison and this mix shows a continuing

acceleration of the phenomenon. At one hundred and twelve days MA can be observed to show

an inferior resistance to the aggressive solution compared with MB, MC, ME and SR. Both mixes

MA and MD contain no addition of GGBS. Mix MD is ordinary Portland CEM I cement while

mix MA represents Portland CEM II-A/L limestone cement. At one hundred and ninety six days

exposure, both mixes ME and SR are beginning to show minor deviations from the continuing

minimal expansion rate of mixes MB and MC.

Figure 4.1 – Mortar prisms expansions following immersion in a 5% sodium sulfate solution

Table 4.1 – American Concrete Institute (ACI) performance guidelines for concrete exposed to sulfate when tested according to ASTM C1012.

Exposure

Level

Exposure

Class

Dissolved sulfate in

water (ppm)

Moderate S1 150 ≤ SO

(Seawater)

Severe S2 1500 ≤ SO

Very severe S3 >10000

*The 12-month expansion limit applies only when the measured expansion

Mix ME is a 30% Portland CEM

resisting cement. Mixes MB and MC are both CEM

and 70% replacement levels of GGBS respect

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 56 112

% E

xp

an

sio

n

Sulfate Expansion Tests

CEM II 100%

CEM II + 70% GGBS

CEM I + 70% GGBS

15

Mortar prisms expansions following immersion in a 5% sodium sulfate solution

Concrete Institute (ACI) performance guidelines for concrete exposed to sulfate when tested according to ASTM C1012.

Dissolved sulfate in

water (ppm)

Max Expansion When Tested Using AS

At 6 months At 18 months

≤ SO42- ≤ 1500

(Seawater)

0.10%

≤ SO42- ≤ 10000 0.05% 0.10%*

>10000

month expansion limit applies only when the measured expansion exceeds the 6-month expansion limit

Mix ME is a 30% Portland CEM I cement with 70% GGBS while SR is a Portland CEM

resisting cement. Mixes MB and MC are both CEM II-A/L limestone cement mortars with 50%

and 70% replacement levels of GGBS respectively. At three hundred and eight days exposure,

168 224 280 336 392 448

Days Exposure

Sulfate Expansion Tests

CEM II 100% CEM II + 50% GGBS

CEM II + 70% GGBS CEM I 100%

CEM I + 70% GGBS SRPC 100%

Mortar prisms expansions following immersion in a 5% sodium sulfate solution

Concrete Institute (ACI) performance guidelines for concrete exposed to

Max Expansion When Tested Using ASTM C1012

At 18 months

0.10%

month expansion limit

I cement with 70% GGBS while SR is a Portland CEM I sulfate

A/L limestone cement mortars with 50%

ively. At three hundred and eight days exposure,

448 504

16

the sulfate resisting mortar SR has now begun to expand beyond the level of mix ME leaving the

three mortars with GGBS as a cement replacement showing the least expansion.

There were some marked differences in visual deterioration of the mixes varying from

corrosion related deposits and discoloration to cracking and warping of the specimens, or a

combination of each. The severity of the visual deterioration corresponds well to the degree of

expansion observed. Examination of each of the test mortar prisms indicated the formation of

longitudinal cracks around 0.035% - 0.04% and this was common to all mixes having reached

this expansion level (Figure 4.3, Figure 4.4 & Figure 4.6). Figure 4.3 and Figure 4.4 show these

longitudinal white-filled cracks along the edges of both the SRPC and CEM II 100% specimens.

The CEM I specimens (both MD and ME) show a similar crack formation although lacking in

any white substance (Figure 4.5 & Figure 4.6). The remaining specimens containing GGBS (MB

and MC) have not yet shown any crack formation.

Longitudinal cracking along the length of the specimens was not an exclusive mechanism

with radial cracking observed on one of the MA specimens along the boundary of the reference

stud (Figure 4.2a). One of the other visual distinctions between MA and MD were notable

depositions of a white substance occurring in blotches at random intervals on one of the prisms

which can be seen in Figure 4.2b. These deposits seemed to be an integral part of the paste and

were not soft to touch, nor had they the ability to be removed by scratching the surface.

(a)

17

(b)

Figure 4.2 – Radial cracking observed around the reference studs (a) and white blotches

appearing on the surface of the prism (b)

Generally however, the appearance of white deposits was less locally concentrated than in

Figure 4.2b and consisted primarily of an intermittent speckled pattern throughout the prisms.

This was applicable to all specimens and mixes after one year except those containing 70%

GGBS as a cement replacement.

Of the specimens whose deterioration has reached an advanced stage (approximately 0.1%

expansion or greater - MA and MD), an increase in the crack density / length appears to be a

common occurrence combined with the earnest commencement of corner spalling. Figure 4.7 (a)

& (b) below show missing corner edges on specimens from mix MA and MD at an approximate

expansion value of 0.1%. There is some evidence of “rounding” of the edges on specimens SR

and ME however they have not reached the extent of spalling observed below.

18

Figure 4.3 – White filled crack drawn parallel to yellow line and indicated by red arrows (SR)

Figure 4.4 – White filled crack drawn parallel to yellow line and indicated by red arrows (MA)

19

Figure 4.5 – Longitudinal crack drawn parallel to yellow line and indicated by red arrows (ME)

Figure 4.6 – Longitudinal crack indicated by red arrows (MD)

20

(b)

Figure 4.7 – Spalling of MA (a) and MD (b) prisms at 0.1% expansion

Simultaneous to this process, increased radial expansion could be observed to begin on

some specimens between approximately 0.2% expansion and 0.45% expansion around the

reference stud (Figure 4.10). Although this stage of deterioration was particularly visible for mix

MD, the initiation of radial cracking was also observed on one on the specimens from mix MA,

as seen in Figure 4.2a, suggesting that this process may be replicated once expansion has reached

an equivalent level.

Figure 4.8 – Spalling of the corners and loss of cohesion of the CEM I mix (MD) after one year’s

exposure

Continuing corrosion could be observed on specimens MD as the acceleration of the

degradation process had significantly advanced with this mix after sixty-four weeks. At fifty-two

weeks exposure and an expansion of approximately 0.3%, a slight warping of one of the prisms

was observed along with the propagation of a crack perpendicular to the surface. At sixty-four

21

weeks the crack had significantly developed and extensive warping was visible (Figure 4.9). This

perpendicular cracking occurred for prisms MD3 and MD4 as these individually had the most

advanced level of expansion.

(b)

(c)

Figure 4.9 (a-c) – Perpendicular crack propagation in mix MD

22

(b)

Figure 4.10 – Onset of extensive radial crack / bulging

Visually, both mixes MA and MD appear to have suffered the most. Cracking and spalling

was widespread after one year for both with white deposits seemingly a prominent feature for the

attack on MA while MD exhibited almost exponential expansion. Mixes MB and MC, the CEM

II/A-L limestone cements with 50% and 70% GGBS respectively, have shown comparatively

little expansion and little differentiation. MB has shown some minor discoloration while MC has

shown no visual evidence of attack. The sulfate resisting cement specimens (SR) have been

outperformed by all mortars containing GGBS either with CEM I or CEM II/A-L after one year.

Visually it has begun to exhibit the same common degradation phenomenon when approaching

0.030% – 0.035% expansion, namely cracking, spalling and a white speckled appearance (the

latter, however, generally beginning to appear within eight weeks).

It can be concluded that within the given testing parameters, there is a clear benefit to the

addition of a high percentage (≥ 50%) of GGBS to mortar. This would seem to be the case

regardless of the cement type used although it would appear to have a greater contribution in

increasing the resistance of CEM I mixtures to sulfate attack. The CEM II/A-L limestone cement

used in this experimental programme exhibits an inherent sulfate resisting capability although

may not be sulfate resistant. When combined with a percentage of GGBS greater than or equal to

50% the resulting mixture exhibits a superior level of sulfate resistance to that of all others tested,

including a standard sulfate resisting Portland cement.

23

4.3 Discussion of sodium sulfate expansion results

Traditionally cements supplied to the Irish market have been of the CEM I variety, however since

2007 there has been a significant change in Irish concrete practice. With manufacturers becoming

concerned at the energy requirements in traditional (CEM I) production and the resulting carbon

footprint, CEM II/A-L cements with additions of approximately 7% limestone have now become

the dominant cement type. This change needs to be incorporated into concrete specification

particularly for projects exposed to chemically aggressive environments. More importantly, the

effect of a chemical attack needs to be sufficiently documented, outlining failure mechanisms and

potential consequences.

The study conducted in this experimental programme looked at the chemical effects that

concrete and mortar may be exposed to at high sulfate levels. The results have indicated that the

CEM II/A-L limestone cement, as used here, appears to possess an inherent sulfate-resisting

capability which can be further enhanced with the addition of 50% or 70% GGBS as a cement

replacement. Existing research on the effect of limestone additions to cement has indicated wide-

ranging consequences varying from beneficial to detrimental (González and Irassar, 1998, Irassar

et al., 2000). Nonetheless a common conclusion seems to centre on an upper limit that provides

an improved resistance and this seems to vary between 15% and 20% (Ramezanianpour et al.,

2009, Irassar et al., 2005). This varying behaviour has been attributed to several possibilities

amongst which are: the dilution effect of cement constituents, permeability and porosity, the

influence of the level of C3A on the system and the level of C3S C2S and calcium hydroxide (CH)

in the hydrated cement paste.

4.3.1 Dilution effect

The dilution effect is simply used to describe the replacement of clinker with a non-cementitious

filler material such as limestone. The latter shows no pozzolanic properties and thus does not

produce C-S-H gel, the main binding component of a hydrated cement paste (Ramezanianpour et

al., 2009). The effect reduces the amount of hydration products reacting during a sulfate attack

and has been attributed by some authors as contributing to the improved resistance in cements

containing minor limestone additions (Hooton, 1990, González and Irassar, 1998). This

improvement can be further enhanced by ensuring the C3A content of the cement is minimized.

24

In the sulfate resistance testing described in the previous section, the C3A values for the CEM I

and CEM II cements were 12.3% and 8.4% respectively as derived from Bogue’s calculations.

While neither value constitutes levels associated with a sulfate-resisting specification, the

reduced percentage may partly account for the better performance of CEM II mixes in the

experimental programme. Nonetheless, several authors have noted the poor performance of

limestone cements even with moderate C3A levels. With this in mind, and given the results

presented, the effect of the percentage limestone added should be given considerable attention.

Table 4.2 – Cement chemical analysis

Composition (% by oxides)

Compound CEM I CEM II/A-L

CaO 60.29 61.18

SiO2 18.24 18.05

Al2O3 6.19 5.46

Fe2O3 2.45 3.61

MgO 3.55 3.66

Mn3O4 0.26 1.15

TiO 0.00 1.28

Na2O 1.17 1.02

K2O 1.32 1.60

P2O5 4.15 0.00

SO3 2.38 2.99

Bogue Equations: C3A = 2.65(Al2O3) – 1.69(Fe2O3)

CEM I: C3A = 2.65(6.19) – 1.69(2.45)

= 12.3%

CEM II/A-L: C3A = 2.65(5.46) – 1.69(3.61)

= 8.4%

4.3.2 Permeability and porosity

There are clearly other questions regarding the nature of the reaction of limestone with both the

cement paste and sulfate ions. Issues surrounding the effect on permeability, porosity and

25

tortuosity are all topics that have been discussed by several authors (Hornain et al., 1995, Tsivilis

et al., 2003, Pipilikaki et al., 2009). It should also be noted that the effective w/c ratio also

increases with an increasing percentage of filler used and this can be attributed to the lack of

pozzolanic properties of limestone (hence it cannot be considered a cementitious material).

According to Gonzalez and Irassar (1998), the capillary porosity depends on the w/c ratio and the

hydration degree and thus this affects the overall porosity of the cement. Tsivilis et al. (2003)

showed that a Portland limestone cement exhibited lower water permeability values when

compared to an ordinary Portland cement; they added however that permeability is not simply a

function of porosity but also of the size, distribution, shape, tortuosity, and continuity of the

pores. Their tests were carried out on specimens that contained a range of between 0% and 35%

limestone. Pipilikaki et al. (2009) however conducted tests that showed Portland limestone

cement containing 35% limestone had a higher porosity than an ordinary Portland cement. The

authors then suggested that this may indicate a higher permeability, thus contradicting Tsivilis et

al. (2003). They make the observation however, that limestone cements have an absence of large

capillaries which may delay the ingress of sulfates and lower initial expansion but stress that the

mechanism by which limestone affects the sulfate resistance of cement is far from being well

understood.

Whether it is due to a decrease in permeability, the absence of large capillaries or simply

the resultant of the dilution effect, what is clear is that the results presented in section 4.2 indicate

a benefit of using CEM II limestone cement with a filler content of between 5 and 10%. The

addition of 50% or 70% GGBS as a cement replacement further enhances the sulfate resisting

abilities and can more than likely be attributed to not only a decrease in permeability associated

with GGBS but also the reduction in calcium hydroxide in the hydrated cement paste.

4.3.3 The Influence of C3A

The level of C3A in the cement is clearly an important characteristic of its sulfate resistance. It is

a compound that contributes little or nothing to cement strength except at early ages where it is

responsible for flash set. It does however, act as a flux and reduces the temperature of burning

clinker and allows the combination of lime and silica (Neville, 1995). Limiting the amount of

C3A in the system reduces the monosulfate (Afm) phase that can lead to the formation of

26

ettringite. This compound greatly contributes to the expansion of cementitious materials and,

along with gypsum formation, is one of the principal sulfate attack mechanisms. Minimising the

amount of C3A forms the basis of a sulfate resisting Portland cement. However, given that all

mixes containing GGBS as a cement replacement exceeded the performance of SRPC mortar

specimens in the experimental programme, it is clear that reducing the potential for ettringite

formation should not be the only preventative measure taken against a sulfate attack.

Examining CEM II cements, the presence of limestone alters the hydration reactions of

C3A according to several authors. Firstly, ettringite formation is accelerated by the presence of

CaCO3 (Bonavetti et al., 2001) and secondly the reaction between the limestone and C3A forms

carboaluminates (González and Irassar, 1998) which compete with monosulfoaluminate stability

and ettringite transformation. With this in mind it is evident that the addition of limestone further

complicates the already complex process of sulfate attack. Gonzalez and Irassar (1998) also

highlight that a high level of C3A extends the interaction of sulfate ions with unstable hydrates in

the mortar. As previously discussed, the level of C3A in both the CEM I and CEM II mixes in the

experimental programme were 12.3% and 8.4% respectively. The 100% CEM I specimen (MD)

showed expansion at one year that was more than three times that of a 100% CEM II specimen

(MA). The inclusion of GGBS as a cement replacement has demonstrably affected the sulfate

performance as evidenced by the low expansion of mixes MB, MC and ME. It has been claimed

that a higher replacement level of a pozzolanic material dilutes the C3A, reduces the aluminate

phases and decreases ettringite formation (Al-Dulaijan et al., 2003, González and Irassar, 1998).

Deterioration in limestone cements has primarily been attributed to gypsum formation while the

mechanism in ordinary Portland cements is dominated by ettringite formation (Pipilikaki et al.,

2009). Irassar et al. (2003) further supports this claim by observing greater gypsum formation in

moderate C3A limestone cements subjected to a 5% sodium sulfate solution as specified in

ASTM C1012.

The concentration of the sodium sulfate solution is also important in deciphering the

dominant form of attack. In solutions with sulfate levels exceeding 8g/l the mechanism is said to

be primarily due to gypsum formation (Hekal et al., 2002, Tosun et al., 2009). The tests carried

out in the sulfate expansion programme contained a sulfate strength of 33.8g/l, more than

exceeding the accepted threshold. This may be further supported by the visual observations of

substantial white deposits on the CEM II limestone specimens. With the CEM I mortars however,

27

the situation may be less clear. Although the solution strength would dictate a gypsum dominated

attack, the deposits of the white substance were considerably less than on the limestone mortars

while cracks tended not to be characterised by white veins.

4.3.4 Influence of C3S and C2S

Both the C3S (alite) and the C2S (belite) contents of the cements are also important indicators of

performance under a sustained sulfate attack. The presence of a limestone additive, such as that in

CEM II-A/L, also modifies the Ca/Si ratio of the C-S-H phase, with the interaction of CaCO3

accelerating the hydration of the C3S content (Ramezanianpour et al., 2009). Alite and belite play

important roles in characterising the strength of a hydrated cement paste, the former contributing

much towards strength at early ages, the latter developing those characteristics as time

progresses. However with an increasing percentage of C3S, the quantity of calcium hydroxide

formed during hydration also increases raising a cement’s vulnerability to gypsum formation

during a sulfate attack (Ramyar and Inan, 2007). Research conducted on pure C3S cement pastes

also demonstrated that even gypsum formation caused considerable expansion (Tian and Cohen,

2000), although this mechanism of attack for cements used in practice is, by the authors’ own

admission, still a cause for considerable debate . Tosun et al. (2009) observed that cement with a

high percentage of limestone and a high C3S/C2S ratio was more prone to attack by sulfates,

however their use of an extraordinarily high sulfate solution (200g/l SO42-) means their

conclusions must be greeted with some scepticism. It is generally regarded that a cement low in

C3S and C3A will perform well during a sulfate attack; nonetheless this may be difficult as it has

been pointed out that reducing the C3A content raises the C3S/C2S ratio (Al-Dulaijan et al., 2003).

4.3.5 Sulfate resisting capabilities of CEM II/A-L and GGBS concretes

Portland limestone cements suffer similar chemical reactions from a traditional sulfate attack as

ordinary Portland cements resulting primarily in the formation of gypsum and ettringite. The

formation of thaumasite is of particular concern given the high level of carbonate in the system;

however there is often a precondition of low temperatures before this becomes a favourable

attack mechanism (Higgins and Crammond, 2003), although this is debatable (Irassar et al.,

2005). Nonetheless the chemical interactions involved in the production of gypsum, ettringite and

28

thaumasite, whether during a sulfate attack or during cement hydration, can be modified in the

presence of limestone. According to Gonzalez and Irassar (1998), during cement hydration

carbonate ions from the limestone filler compete with sulfate ions from gypsum to react with

aluminate ions from C3A forming monocarboaluminate, monosulfoaluminate and ettringite.

Irassar et al. (2003) detailed the sequence of a sulfate attack concluding that diffusion of sulfate

ions is followed by calcium hydroxide leaching, ettringite formation, gypsum formation and

depletion of CH. The latter stages involve the decalcification of C-S-H followed by thaumasite

formation.

The sequence of attack would corroborate well with what was noted in the experimental

results in section 4.2. As observed with CEM II/A-L limestone mix MA, there was an initial low

level expansion detected with very little visual deterioration which could indicate the onset of

ettringite or early gypsum formation. As the attack progressed white deposits began forming on

the exterior of each prism, followed by a lack of cohesion and spalling at the edges, possibly

indicating the decalcification of the C-S-H phase. Irassar et al. (2003) also describe corrosion of

edges and corners and attribute it to gypsum formation in parallel veins to the sulfate attack front.

As seen in Figure 4.4 cracks / veins with a white deposit can be observed at the elapsed exposure

time when the specimen began to shed mortar particles. Almost identical attack sequences were

observed in all mortar mixes undergoing observable degradation suggesting that none of these

phenomena are particularly unique to limestone cements. The CEM I specimens of MD however,

exhibited less visual evidence of white deposits and more physical effects in the form of

cracking, warping, spalling and surface delamination. This could perhaps be attributable to a

more dominant stage in the attack sequence compared to those observed in limestone cements.

In examining the results of the sulfate expansion experimental programme, it is clear that

the addition of a relatively high percentage of GGBS to both CEM I and CEM II mortars has had

a significant effect on their resistance to a 5% sodium sulfate solution. Both the CEM II mortars

(MB and MC) have shown the least amount of expansion and visual deterioration while the

CEMI I mortar with 70% GGBS (ME) has shown a resistance equalling SRPC for the majority of

the exposure period but eventually exceeding it. The sulfate resisting capabilities of GGBS have

been discussed on many occasions (BRE, 2003, Higgins and Crammond, 2003) with much of the

benefit being attributed to a denser matrix, decreased permeability and a reduction in calcium

hydroxide present in the hydrated system (Pavía and Condren, 2008, Al-Dulaijan et al., 2003,

29

Osborne, 1999). Furthermore, with the formation of a secondary C-S-H phase attributable to the

interaction between calcium hydroxide and GGBS, much of the alumina in the system becomes

‘locked up’ in this product and is not available to form ettringite during a sulfate attack (Gollop

and Taylor, 1996). The author’s also claim that as the percentage replacement of cement with

GGBS increases the proportion which reacts decreases with cement and this limits the quantity of

alumina released at high slag contents.

The combination of a reduction in calcium hydroxide, decreased permeability and the

‘locking up’ of potentially reactive alumina may account for the behaviour of the CEM I mortars

but it is essential to investigate any further effects of CEM II cements with a limestone addition.

The results presented above have indicated the potential increased benefit of using this with at

least 50% GGBS as a cement replacement. As previously discussed, limestone cements have an

absence of large capillaries which may delay the ingress of sulfates (Pipilikaki et al., 2009).

When combining this with the more impermeable matrix from GGBS cements, the opportunity

for sulfates to interact with the cement compounds is being severely limited. Visually, all

specimens containing GGBS have exhibited almost no evidence of a lack of cohesion from

exposure to the sulfate solution. Researchers (Brown and Taylor, 1999) have attempted to

account for this effect in limestone cements and have put forward a plausible explanation. With

an increase in GGBS levels, there is also an increase in hydrated C-S-H in the system.

Correspondingly, there is a decrease in the level of calcium hydroxide. Ettringite and gypsum

preferentially obtain their calcium from this phase but in the absence of a sufficient quantity

available, calcium from the C-S-H phase will serve as a source. This phase constitutes the

primary binding capability of a cement matrix and its degradation leads to a major loss in

cohesion. The author’s claim that by adding calcium carbonate (limestone) as an additive, this in

turn will serve as the source of calcium for ettringite and gypsum thus preserving the integrity of

the C-S-H phase.

4.4 Sulfuric acid test results

4.4.1 Mass loss results

The measurement of a loss of mass of the concrete specimens was considered an acceptable

means of assessing the performance of each of the mixes in a sulfuric acid environment and was

30

previously used by Chang et al. (2005). The results of the first technique, using a wire brush, are

presented in Figure 4.11. The results of this procedure indicate that there may be a slight increase

in mass over the first twenty-eight days of exposure or very little mass loss. The concrete made

from CEM II-A/L limestone cement with no addition of GGBS showed a higher initial gain in

mass compared to the five other mixes, although the amount could be regarded as not significant.

After the initial month of exposure the decrease in mass remained constant for the most part with

little divergence from this trend. The performance of each of the six mixes remained largely

unchanged following completion of the testing programme, regardless of GGBS content or

cement type. Although the figures indicate that a 70% GGBS content, regardless of cement type,

performed the best throughout the testing period, the difference between the mix which

performed the worst (SRPC) was considered to be not significant. This is confirmation of the

aggressive nature of the sulfuric acid solution and the inherent difficulties in exposing

cementitious materials to this type of environment.

The graph in Figure 4.12 shows the results from exposure to the acid without using the

brushing technique. It can be seen that there is a slight increase in mass for all specimens within

the first twenty-eight days following which there is a steady increase in mass loss. This continues

at a similar rate until eighty-four days at which point there appears to be a small decrease in the

rate of mass loss for the unbrushed specimens compared with those that have been brushed at

weekly intervals. This point can be illustrated by Figure 4.13. The phenomenon appears to

coincide with the dissolution of the outer layer of the cement matrix and the protrusion of the

10mm and 20mm limestone aggregate although this apparent relationship does not seem

applicable to the brushed experiment.

31

Figure 4.11 – Mass loss (brushed concrete)

Figure 4.12 – Mass loss (unbrushed concrete)

-10000

-8000

-6000

-4000

-2000

0

2000

0 56 112 168

Ma

ss L

oss

(g

/m^

2)

Days Exposure

Brushed Concrete

CEM II 100%

CEM II + 50% GGBS

CEM II + 70% GBS

CEM I 100%

CEM I + 70% GGBS

SRPC

-10000

-8000

-6000

-4000

-2000

0

2000

0 56 112 168

Ma

ss L

oss

(g

/m^

2)

Days Exposure

Unbrushed Concrete

CEM II 100%

CEM II + 50% GGBS

CEM II + 70% GBS

CEM I 100%

CEM I + 70% GGBS

SRPC

32

.

(b)

(c) (d)

(e) (f)

Figure 4.13 (a-f) – Comparison of brushed/un-brushed mass loss results

-10000

-8000

-6000

-4000

-2000

0

2000

0 28 56 84 112 140 168

Ma

ss L

oss

(g

/m2

)

Days Exposure

CEM II 100%

Unrbrushed

Brushed

-10000

-8000

-6000

-4000

-2000

0

2000

0 28 56 84 112 140 168

Ma

ss L

oss

(g

/m2

)

Days Exposure

CEM II + 50% GGBS

Unbrushed

Brushed

-10000

-8000

-6000

-4000

-2000

0

2000

0 28 56 84 112 140 168

Ma

ss L

oss

(g

/m2

)

Days Exposure

CEM II + 70% GGBS

Unbrushed

Brushed

-10000

-8000

-6000

-4000

-2000

0

2000

0 28 56 84 112 140 168

Ma

ss L

oss

(g

/m2

)

Days Exposure

CEM I 100%

Unbrushed

Brushed

-10000

-8000

-6000

-4000

-2000

0

2000

0 28 56 84 112 140 168

Ma

ss L

oss

(g

/m2

)

Days Exposure

CEM I + 70% GGBS

Unbrushed

Brushed

-10000

-8000

-6000

-4000

-2000

0

2000

0 28 56 84 112 140 168

Ma

ss L

oss

(g

/m2

)

Days Exposure

SRPC 100%

Unbrushed

Brushed

33

(a) (d)

(b) (e)

(c) (f)

Figure 4.14 – Typical corrosion levels for brushed concrete at 28, 56 & 84 days (a-c) and

unbrushed concrete over the same time intervals (d-f). Note differing degree of aggregate

exposure.

34

For both experiments there is very little between the performances of each of the six

different mixes in terms of mass loss or compressive strength. Although the data seems to suggest

that an addition of 70% GGBS improves the resistance to mass loss after six months, this must be

seen in the context of the compressive strength losing at least 60% of its 28-day value regardless

of the cement type or brushing technique used (Figure 4.17).

Several useful observations can be gleaned from the obtained data. It is clear that the use of

brushing to mimic abrasive behaviour (e.g. flowing water) has an effect on the loss of material

from the surface of concrete. (Figure 4.14 a-f). Allowing build-up to occur may slow down some

aspects of the corrosive effects of acid, albeit on a superficial basis, as clearly there are internal

chemical transformations occurring. This is again demonstrated by Figure 4.19 showing the

failure mechanism of a cube exposed to acid for six months. It is evident that a total loss of

cohesion has occurred throughout the specimen proving that while much of the ongoing reactions

are surface oriented there are more sinister forces at work beneath the cube surface. Furthermore,

there may be a useful relationship between the initial visibility of exposed aggregate and the

underlying state of the concrete integrity exposed to acidic environments as the cube strength

data reveals.

4.4.2 Discussion of deterioration mechanism

For both the brushed and unbrushed experimental programmes the primary mechanism of

deterioration was disintegration of the cement matrix along with some secondary spalling. There

was no evidence of cracking at any point over the six month exposure period. The manifestation

of the deterioration consisted of the formation on the surface of the cube specimens of a white

mushy substance (most likely gypsum) that was soft to touch and easy to remove. This was

visible after approximately one week of exposure to the acid and built up following each

successive removal of loosely adhering corrosion products. Regular examination of the

unbrushed concrete cubes also revealed the complete loss of cohesion of the surface layer of the

cement matrix after twelve weeks.

35

Figure 4.15 – Complete surface delamination of one side of a 100mm cube exposed to 1% sulfuric acid (unbrushed)

Figure 4.16 – Concrete material losing cohesion and falling off the specimens

The type of deterioration visible showed the entire side of a cube fall away as a single piece

and this can be seen in the highlighted section of Figure 4.15. Regular examination of the brushed

36

specimens confirmed the mechanism of deterioration with material falling off the sides and

corners of the specimen and gathering at the bottom of the tank. This can be seen in Figure 4.16

and was a characteristic present throughout the duration of the experimental programme

(including that of the unbrushed specimens).

4.4.3 Cube strength tests

The experimental programme also examined the cube strengths of each of the mixes at twenty-

eight, fifty-six and one hundred and sixty eight days.

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days

MA - 100% CEM II A/L

Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days

MB - CEM II A/L + 50% GGBS

Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days

MC - CEM II A/L + 70% GGBS

Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days

MD - 100% CEM I

Cubes in water

Cubes in acid

37

Figure 4.17 – Comparison between cube strength exposed to water only and 1% sulfuric acid

only (brushed)

4.4.4 Sulfuric acid expansion tests

Simultaneous to tests conducted on concrete cubes exposed to sulfuric acid, two prisms from

each mix were immersed in a 1% sulfuric acid solution while two were immersed in water over a

six-month period. The solution pH was kept at approximately 1.5 and refreshed at monthly

intervals where the acid was renewed and the containers cleaned of any debris. The change of

length of the prism from the initial reading is then calculated according to

Eqn. 1. The change in length of each of the specimens was measured

twice for accuracy and the results obtained are available in Appendix H.

The data showed that no appreciable expansion occurred and in fact minor contractions

were observed across all six mixes. The change in length of each of the specimens was measured

twice for accuracy, however it was found that at times there were differences between readings

from the same specimen, sometimes significant. It was concluded that the observed changes in

length may be due to experimental error and in fact relatively little movement was observed. The

procedure for measuring the specimens differed from those of the sulfate expansion tests in that a

metal ball had to be placed between the reference studs therefore minor deformities could not be

accounted for across the sphere. The reading on the comparator was also observed to vary

considerably while the specimen settled into the base groves. Again this behaviour was not

observed for the sulfate prism tests. According to Monteiro et al. (2008), an expansion of 0.5%

for concrete exposed to elevated sulfate levels was deemed as the failure point. As can be seen

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

Days

ME - CEM I + 70% GGBS

Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

Str

en

gth

(M

pa

)

Days

SR - 100% SRPC

Cubes in water

Cubes in acid

38

from the experimental results, following six months of exposure to acid the movement in the

prisms was exceptionally far removed from this figure. The determination was that change of

length was not considered a significant contributor to concrete degradation when exposed to

sulfuric acid.

4.5 Ultrasonic results

4.5.1 Stiffness loss in due to sulfuric acid testing

The results in the previous section have shown the potential use for the application of ultrasonic

analysis of concrete, in conjunction with the shear wave detector algorithm developed by Bonal

et al. (2008), to monitor stiffness development in mixes containing varying percentages of

GGBS. In theory the same process has the potential to be used in recording the loss of stiffness in

concrete exposed to aggressive chemical environments. The technique is now applied to monitor

the degradation of 100mm cubes made with five concrete mixes with varying percentages of

GGBS, and one sulfate resisting SRPC mix, exposed to a 1% solution of sulfuric acid (H2SO4)

over a six month period. The cement type and percentage of GGBS used as a cement replacement

is indicated in the table below.

Table 4.3 – Concrete mix designations for sulfuric acid tests

Mix Designation Cement Type % GGBS

MA CEM II 0

MB CEM II 50

MC CEM II 70

MD CEM I 0

ME CEM I 70

SR SRPC 0

Photographic observation of the cube specimens indicated the acid attack was primarily

focused on the cement matrix with the limestone aggregate largely avoiding the corrosive effects

39

(Figure 4.18). Failure of the specimen was by complete loss in cohesion of the binding properties

(Figure 4.19). The ultrasonic analysis therefore takes two approaches: monitoring the degradation

of concrete as a single inhomogeneous material and then again by considering it as a two-phase

model consisting of mortar and coarse aggregate. By doing this, it can be assumed that the cause

of a loss in stiffness in concrete is attributed to complete disintegration of the cement matrix

leaving the aggregate assumed to be unaffected by the acid.

Figure 4.18 – Condition of a cube following six months exposure to sulfuric acid. The aggregate remains largely unaffected while the cement matrix has suffered spalling and disintegration.

Figure 4.19 – The same cube tested under compression until failure. The mode of failure clearly indicates a loss of cohesion in the binding properties of the cement matrix.

In order to separate the concrete into a two

permits the velocity of an ultrasonic wave through concrete to be written in terms of the velocity

of the mortar component and the velocity of the coarse aggregate component

� � =

��

Where νC is the velocity in concrete,

aggregate, VM is the volume of mortar, V

volume of concrete. By calculating the volume of coarse aggregate per 100mm cube specimen,

the phase was then considered as a single layer of limestone 46mm deep, the remaining 54mm

being the mortar phase. With volume parameters and the velocity of

large specimen of limestone the ultrasonic velocities were also determined for the “coarse

aggregate” phase. The transmission of the signal through air voids and pores and the possible

effects of this were not considered.

Figure 4.20 – S-wave signal from the solid limestone showing the first arrival point as determined by the shear wave detector algorithm

Re-arranging the equation yields an expression for the velocity of an ultrasonic wave in

mortar, where νCA is now the velocity through the solid

� � = � �

� × ��

Am

pli

tud

e (m

icro

-Vo

lts)

40

In order to separate the concrete into a two-phase system, a model was developed that

an ultrasonic wave through concrete to be written in terms of the velocity

of the mortar component and the velocity of the coarse aggregate component (Lin et al., 2003)

Eqn. 2

is the velocity in concrete, νM is the velocity in mortar, νCA is the velocity in coarse

is the volume of mortar, VCA is the volume of coarse aggregate and V



being the mortar phase. With volume parameters and the velocity of concrete known, using a



effects of this were not considered.

wave signal from the solid limestone showing the first arrival point as determined by the shear wave detector algorithm

arranging the equation yields an expression for the velocity of an ultrasonic wave in

is now the velocity through the solid limestone layer:

�� × �� Eqn 3

Time (ns)

phase system, a model was developed that

an ultrasonic wave through concrete to be written in terms of the velocity

(Lin et al., 2003).

is the velocity in coarse

is the volume of coarse aggregate and VC is the



concrete known, using a



wave signal from the solid limestone showing the first arrival point as

arranging the equation yields an expression for the velocity of an ultrasonic wave in

Eqn 3

41

4.5.2 Stiffness loss in concrete exposed to a 1% sulfuric acid solution

Ultrasonic testing was carried out on two samples stored in water and two samples stored in a 1%

sulfuric acid solution at twenty-eight day intervals for each of the six concrete mixes. The results

for those specimens made from CEM II-A/L with 0%, 50% and 70% GGBS used as a cement

replacement are presented in Figure 4.21, Figure 4.22 and Figure 4.23 respectively. It can be seen

that determining the small strain Young’s modulus using the shear wave detector algorithm has

the ability to monitor the degradation of concrete exposed to a 1% sulfuric acid solution. There is,

however, a difficulty in distinguishing between the six-month performances of each mix

individually, perhaps reflecting the aggressive nature of the solution in which they are stored.

Cubes containing both 50% and 70% GGBS, though, show a small resistance to a drop in the

small strain Young’s modulus up to approximately eighty-four days with the 70% GGBS

apparently showing almost complete resistance up to this point. This apparent beneficial

performance of GGBS may be somewhat misleading however, as the fifty-six day cube strengths

(for those exposed to acid) actually show a 46% drop (70% GGBS) and 42% (50% GGBS) drop

compared to those stored in water (Figure 4.17). The mix containing 0% GGBS showed the least

drop in strength recording a loss of only 30% in comparison. This brings up an interesting

possibility as to how GGBS may be affecting ultrasonic velocities in limestone concrete. As can

be seen from the results documenting early age strength gain, the small strain Young’s modulus

follows the trends of both the cube strengths and that of the static Young’s modulus much more

closely. At this early stage in hydration many of the chemical compounds giving concrete its

strength (and in particular GGBS concretes) have yet to be formed. The results also show that by

treating the concrete as a two-phase system, degradation of the mortar phase closely mimics the

trend of the system as a whole giving confidence in the fact that the disintegration of concrete can

be attributed to the loss in cohesion of the cement matrix.

42

Table 4.4 – Sample data set obtained from the ultrasonic experimental programme. Values are

obtained up to week 24 for two samples stored in water and two stored in 1% sulfuric acid for

each time step.

Mix:

MB

Calculation of Shear and Dynamic Modulus

Week Cube TP-wave

(sec)

VP-wave

(m/sec)

TS-wave

(sec)

VS-wave

(m/sec)

Density

(kg/m3)

Poissons

ratio

‘G’

(GPa)

‘E’

(GPa)

0 6 21.00 4975 31.0 3279 2400 0.116 25.8 58

0 12 20.40 5128 31.6 3215 2400 0.176 24.8 58

4 … … … … … 2400 … … …

4 … … … … … 2400 … … …

Figure 4.21 – Ultrasonic analysis of small strain Young’s modulus for mix MA immersed in 1% sulfuric acid

0

10

20

30

40

50

60

70

0 28 56 84 112 140 168

Sm

all

Str

ain

'E

' (G

pa

)

Days Exposure to 1% Sulfuric Acid

Ultrasonic Analysis (CEM II/A-L 100%)

Cubes in Water Cubes in Acid

Mortar in Water Mortar in Acid

43

Figure 4.22 – Ultrasonic analysis of small strain Young’s modulus for mix MB immersed in 1% sulfuric acid

Figure 4.23 – Ultrasonic analysis of small strain Young’s modulus for mix MC immersed in 1% sulfuric acid

The results of the second set of three mixes detail the performance of CEM I with 0% and

70% GGBS as a cement replacement (Figure 4.24 and Figure 4.25). The performance of a

sulfate-resisting SRPC mix is also considered as a benchmark (Figure 4.26). Again it is clear that

the ultrasonic analysis has the ability to detect concrete degradation in the latter stages of the

0

10

20

30

40

50

60

70

0 28 56 84 112 140 168

Sm

all

Str

ain

'E

' (G

pa

)


Ultrasonic Analysis (CEM II/A-L + 50% GGBS)


Mortar in Water Mortar in acid

0

10

20

30

40

50

60

70

0 28 56 84 112 140 168

Sm

all

Str

ain

'E

' (G

pa

)


Ultrasonic Analysis (CEM II /A-L + 70% GGBS)



44

experimental programme. The performance of the three mixes is somewhat ambiguous in the first

fifty-six days with little differences being recorded between those specimens stored in water and

those stored in acid. This again is somewhat misleading as the recorded cube strengths (see

Figure 4.17) begin to show a substantial loss in compressive resistance by this stage in the

programme. Furthermore, the ability to distinguish between the performance of a CEM I mix, a

CEM II-A/L mix and those containing GGBS is minimal. It is also clear that up to the time frame

between fifty-six days and eighty-four days it may be difficult for this method to detect any

degree of loss in stiffness.

The loss in concrete strength shown in Table 4.5 above indicates that regardless of the

cement type used the performance of each of the mixes after six months exposure to the acidic

solution is poor showing very little difference in the ability to resist the aggressive environment.

Given that the results of the ultrasonic tests also show few differences after six months, it could

be hypothesised that the method is indeed a reliable indicator in the latter stages of attack,

although seemingly less sensitive than the behaviour shown in the early age stiffness

development tests.

Table 4.5 – Percentage loss in strength after six months exposure to a 1% sulfuric acid solution

Mix Designation % loss in strength

MA 65%

MB 74%

MC 66%

MD 76%

ME 74%

SR 72%

45

Figure 4.24 – Ultrasonic analysis of small strain Young’s modulus for mix MD immersed in 1% sulfuric acid

Figure 4.25 – Ultrasonic analysis of small strain Young’s modulus for mix ME immersed in 1% sulfuric acid

0

10

20

30

40

50

60

70

0 28 56 84 112 140 168

Sm

all

Str

ain

'E

' (G

pa

)


Ultrasonic Analysis (CEM I 100%)



0

10

20

30

40

50

60

70

0 28 56 84 112 140 168

Sm

all

Str

ain

'E

' (G

pa

)


Ultrasonic Analysis (CEM I 70% GGBS)

Morar in Water Cubes in Water

Cubes in Acid Mortar in Acid

46

Figure 4.26 – Ultrasonic analysis of small strain Young’s modulus for mix SR immersed in 1% sulfuric acid

4.5.3 Discussion of ultrasonic results

There remains a distinct lack of in-depth knowledge into the relationship between ultrasonic

velocities and the development or degradation of stiffness in concrete. Much of the discussion

centres around two aspects of concrete: the microstructural make-up of the mix and the influence

of hydration products (and consequently corrosion products). The ultrasonic results presented

show that the shear wave detector algorithm appears to be more sensitive to a change in stiffness

in the early days of hydration but less so when monitoring the effects of corrosion due to sulfuric

acid attack. To account for these differences it is essential to outline the factors affecting both

processes.

4.5.4 Microstructural Effects

Three parameters within the microstructural make-up of a concrete mix have been attributed to

variations in ultrasonic pulse velocities: entrapped air voids, the water/cement ratio and the

arrangement of aggregate in the mix. For concrete in the early stages of hydration it has been

shown that the velocity of p-waves are slow to develop (Robeyst et al., 2008) but, as can be seen

from the results achieved in the early age tests in section 4.4.1, this begins to approach an

asymptotic value after a few days of hydration for both P-waves and S-waves.

0

10

20

30

40

50

60

70

0 28 56 84 112 140 168

Sm

all

Str

ain

'E

' (G

pa

)

Days Expsoure to 1% Sulfuric Acid

Ultrasonic Analysis (SRPC 100%)

Mortar in Water Cubes in Water

Cubes in Acid Mortar in Acid

47

Figure 4.27 – Development of P-wave and S-wave velocities in early age stiffness development

Robeyst et al. (2008) showed that it was in the first twenty-four hours that the greatest gain

in P-wave velocity was observed. With regard to the ultrasonic tests carried out on specimens

exposed to sulfuric acid, there was almost no effect on the P-wave velocity over the six-month

experimental period with it generally remaining at a consistent level for all mixes. This is

interesting as it has been claimed that P-wave velocity is directly related to the dynamic Young’s

modulus (Voigt et al., 2005). Clearly however, the observed drop in cube strengths (Figure 4.17)

show that the stiffness decreased over the exposure period. This would seem to indicate that P-

wave velocities may solely be an indicator of cement particle interconnectivity and not

necessarily of stiffness (i.e. there may be bonds but they might be weak). In a hydrating mix, for

instance, cement particles remain in suspension for a period and the wave paths thus remain

elongated due to the presence of entrapped air voids (Lee et al., 2004, Chaix et al., 2006, Robeyst

et al., 2008), thus increasing the time from transmitter to receiver. With regard to a specimen

degrading from exposure to sulfuric acid, the cement particles are not in a fluidic suspension and

remain bonded, although perhaps with increasing weakness as time progresses. It may also be

hypothesised that the corrosion products formed in the acid attack (e.g. gypsum) may fill the air

voids providing an unobstructed wave path and masking the effects of a loss of stiffness on P-

wave velocities. This type of behaviour occurs during hydration when primary ettringite serves as

a medium through which p-waves can travel, giving a false indication of stiffness development.

2000

2500

3000

3500

4000

4500

5000

5500

0 5 10 15 20 25

Ve

loci

ty (

m/s

)

Time (Days)

P-wave velocity

S-wave velocity

48

The effect of the water to cement ratio also has a bearing on the velocity of ultrasonic

waves in concrete. Although for this experimental programme the value was constant at 0.45, it is

still worthwhile to mention the effect it has on the cementitious system. According to one group

of authors, for concrete with a w/c ratio greater than 0.5 an increase in aggregate content will lead

to an increase in ultrasonic velocity but with little increase in strength. Conversely, for a high w/c

ratio an increase in cement content will lead to a decrease in ultrasonic velocity while for a low

w/c ratio the velocity doesn’t change as the cement matrix is already dense. The increase in w/c

ratio effectively increases the distance between cement particles, complicating wave transmission

by the non-direct path from transmitter to receiver while the degree of tortuosity of the paste also

has a similar effect (Lee et al., 2004). Furthermore as concrete is not a homogeneous material, it

cannot be said with certainty how the transmission of waves through aggregate-paste boundaries

affects the received signal.

While the influence of air voids and the interconnectivity of cement particles obviously

affect ultrasonic velocities, this merely takes into account the microscopic variabilites. Those

particles on a much larger scale, however, cannot be ignored. The internal settling of aggregate

leads to an increase in ultrasonic velocity while the downward movement during compaction

must also be taken into account. Lin et al (2003) also point out that the distribution of aggregate

within a specimen may have an unexpected effect on the ultrasonic velocity. If the aggregate is

concentrated along the direct line from the ultrasonic transducer transmitting the signal to the

receiver then naturally the wave will travel through more aggregate and the velocity of the wave

will be high. However, if the aggregate is sparse around this line then the velocity will be

comparatively low. This may be an issue for laboratory prepared concrete due to individual

compaction techniques and could differ from that found on site.

4.5.5 Chemical effects

The lack of a substantial difference in performance of concrete exposed to sulfuric acid means it

is quite difficult to pinpoint any effects rising from the presence of limestone in the cement or

indeed that of GGBS. As a result much of what can be discussed arises from the early age tests

but nonetheless may contribute to the performance of the sulfuric acid programme. Both the

formation of primary ettringite during hydration and the effect of the CSH phase subsequently

49

have been found to contribute to variations in ultrasonic velocities. Concretes made with GGBS

form a greater degree of CSH due to the interaction between the former and hydrated calcium

hydroxide. The resulting linkages between cement grains and aggregates provide a path for wave

propagation increasing the velocity. The CSH phase is the main binding compound in concrete

but in concretes made with GGBS this takes time to develop. In early ages tests the 70% GGBS

mix showed the slow development of both velocity and small strain stiffness reflecting the lack

of appreciable CSH formed. After the cubes are immersed in sulfuric acid, the effect may not be

so clear. Both mixes with 70% GGBS (MC and ME) show an early reluctance to a decrease in

small strain stiffness up to eighty-four days, thereafter however, the trend is downward. The

mixes without GGBS (MA and MD) show a drop in small strain Young’s modulus relative to an

initial value. However the final result for all mixes is rather uniform possibly reflecting the

aggressiveness of the environment.

With regard to ettringite formation, this may be more applicable to the early age tests.

Ettringite is unstable in pH values below approximately 11 after which it decomposes. The

sulfuric acid tests are carried out in a solution that has a pH of approximately 1.5 and it could be

assumed that the presence of ettringite is neglected when assessing the ultrasonic results of

concrete in this environment. Nevertheless it has been pointed out that the formation of primary

ettringite during hydration contributes to an increase in p-wave velocity but this has no bearing

on the strength or stiffness of concrete. The ettringite needles fill the pore space previously

occupied by water with a solid product decreasing the space filled with air voids and allowing the

transmission of ultrasonic waves. It could be hypothesised that when concrete is attacked by the

sulfuric acid, forming gypsum and filling the voids of the surrounding spaces, the same behaviour

may occur and affect an accurate assessment of the material’s stiffness.

4.6 Permeability, absorption and sorptivity results

The following table presents the results from the experimental programme.

50

Table 4.6 – Permeability and absorption results

Mix Air permeability

(ln(m2)/s)

Water permeability

(m3/min

0.5)

Absorption

(m3/min)

Sample a Sample b Sample a Sample b Sample a Sample b

MA -0.054 -0.028 3.87E-08 1.78E-08 1.56E-08 2.27E-08

MB -0.047 -0.013 2.35E-08 1.30E-08 5.07E-09 4.04E-09

MC -0.055 -0.018 3.12E-08 1.96E-08 2.59E-08 1.59E-08

MD -0.073 -0.015 7.57E-08 2.68E-08 3.97E-08 1.45E-08

ME -0.034 -0.014 4.07E-08 2.15E-08 2.44E-08 2.56E-08

SR -0.082 -0.006 6.44E-08 2.25E-08 5.35E-08 1.70E-08

The goal of the permeability and sorption testing was to ascertain a performance ranking of the

six concrete mixes. The results of the investigation proved somewhat inconclusive with obtained

values at times differing significantly for identical mix specifications. The results may be due to

experimental error, as the Autoclam requires a completely sealed testing surface, or due to the

effect that aggregate has on the diffusion characteristics of the concrete.

51

5 DISCUSSION

5.1 Sulfate experimental programme

While it has been stated that testing through sulfate exposure to assess concrete tolerance to

wastewater applications is largely an inaccurate method (Monteny et al., 2000), it is clear that this

particularly important fact has not been accepted or realised within the engineering community.

The sulfate testing procedure in this experimental programme was designed to highlight any

variations in the performance of CEMI I, CEM II-A/L and various combinations of GGBS when

compared to SRPC, the standard specification cement for wastewater applications. The results of

the investigation highlighted some very significant differences in the attack mechanism compared

with results obtained in sulfuric acid exposure tests and the conditions observed in two

wastewater treatment plants at Swords in North Co. Dublin and Kilkenny in the midlands. While

the condition of the concrete in both plants resembled the effects of the acid tests the sulfate

testing programme yielded starkly differing results.

Several significant behavioural differences were monitored over the course of the

investigation; while the specimens submersed in a 50g/l sodium sulfate solution exhibited

expansion, cracking and warping those in acid showed only mass loss and disintegration of the

cement matrix. The manifestation of attack also progressed at different paces. While the prisms in

the accelerated sulfate tests took several weeks, sometimes months, to show appreciable

expansion or appearance of corrosion products (other than the CEM I 100% specimens), the

cubes submersed in the 1% sulfuric acid solution began to deteriorate within days. These cubes

rapidly began to show build-up of a white mushy material followed then by mass loss. This

clearly shows that exposure to sulfuric acid is a more aggressive form of attack and may result in

substantially decreased service life estimates. The sulfate tests also demonstrated the ability to

significantly distinguish between the performances of CEM I, CEM II-A/L, SRPC and various

additions of GGBS. Throughout the experimental programme the cement paste of each prism

largely remained intact. Minimal build up of any corrosion products was observed and only the

extreme corners of the specimens showed any mass loss. These behavioural differences call into

question the differences in the chemical makeup of both the solutions used. While each contains a

sulfate ion, traditionally considered the main aggressor, the presence of a H+ ion from the sulfuric

acid solution is clearly having the most detrimental effect resulting in a lack of cohesion and an

52

effective dissolution of the cement matrix. With regard to the sulfate testing procedures, further

investigations into the mechanism of attack may be investigated by modifying the solution by

using magnesium sulfate for example. Research has suggested that this attacks primarily the CSH

phase of cement rather than calcium hydroxide in order to obtain the calcium used in its

degradation process. It is unclear whether this may be a more beneficial test to conduct in

conjunction with sulfuric acid tests; however sodium sulfate has generally been recognised as the

standardised solution for sulfate exposure and is used by both the ASTM C1012 and the Dutch

CUR 48 tests.

It can be concluded that in the context of concrete in wastewater applications, standard tests

to investigate the sulfate performance of a variety of mixes cannot be considered as a reliable

indicator for representing in-service conditions. The tests carried out in this experimental

investigation, however, have highlighted the necessity to affect a change in practice when

specifying concrete for aggressive wastewater applications. The stark contrast in both the

manifestation of corrosion and the physical effects on the cementitious system serve as proof that

this is an urgent requirement that needs to be accounted for. What’s most alarming, however, is

that there appears to be an inability for any concrete to survive this acidic environment despite

the mix being designed to EN 206 XA3 class, deemed the most resistant specification against

chemical attack. It should be noted however that the test solution of pH 1.5 represents the most

severe conditions to be expected in service. The pH may vary in reality on account of

environmental conditions, including temperature and humidity, which undoubtedly affect the

activity of the sulfuric acid producing bacteria. Sulfate tests may draw a concrete specifier into a

false sense of security and while this may satisfy the requirements of current standards, it is clear

that it does not satisfy the true nature of the problem.

5.2 Sulfuric acid programme

A search of existing literature yielded a general consensus that an appropriate procedure for

mimicking the aggressive conditions present in wastewater treatment systems was through the

exposure of concrete to a 1% solution of sulfuric acid (H2SO4) (Chang et al., 2005, Monteny et

al., 2000). The results from this experimental procedure showed that after six months of

exposure, the cubes (which were regularly brushed) lost at least 65% of their strength. Chang et

53

al. (2005) showed reductions in strength not exceeding 30% for five out of six cases over an

identical time period and using a similar experimental regime, although only two of those were

mixes similar to this programme. A contributing factor toward the authors’ result however may

be to what extent the specimens are brushed. Chang et al. (2005) recorded rinsing the specimens

under flowing water and gently brushing them of loose material with a wire brush. The brushing

conducted in this investigation varied from extensive removal of loose material with regular wire

brushing and then again using only flowing tap water to rid the cube of excess build-up. A small

decrease in the rate of mass loss was noted after eighty-four days using the rinsing method

although the differences may be regarded as not significant. The extent of brushing was an

important part of the regime as the idea was to create conditions representative of the bacterial

environment detailed in the literature review. It is unclear whether the assumption of a 1%

sulfuric acid solution is representative of the in-service conditions but it may, however, constitute

an acceptable component in an accelerated test method. The effect of various brushing techniques

yields results that are also far from conclusive and may confirm the suspected intolerance of

concrete to aggressive sulfuric acid environments regardless of the effects of abrasion.

The acid testing programme also raised concerns over the use of sulfate resisting Portland

cement in wastewater applications. It now appears there is a common misconception that

specifying a SRPC mix will sufficiently resist the expected aggressive sulfate environment.

While this is not entirely untrue (some industries such as the brewing industry discharge sulfate-

laden waters from their production processes), it is clear that some form of extra protection is

required for these treatment systems to adequately resist the acidic conditions over a long period

of time. The results presented in this investigation show almost no benefit in using GGBS.

Despite the reduced amount of calcium hydroxide (and the resulting lesser quantities of gypsum

formed as a result of sulfuric acid attack), this does not account for any improvements in the

performance of GGBS concrete. This calls into question other factors such as the possible

increased capillary effect of the GGBS mixes, from decreased pore sizes, or more likely the

dissolution effect of the hydrogen ion of the sulfuric acid. The results from the sulfate prism tests

further highlight the differences in attack mechanisms despite many of the same corrosion

products (i.e. gypsum) being present in both instances.

The sulfuric acid tests in this investigation, while highlighting the vulnerabilities to acidic

conditions, suffer from some inaccuracies inherent in accelerated testing. As has been mentioned,

54

the attack present in wastewater systems is bacterial in nature (not purely chemical), evolving

over a period of time far exceeding the six months used in this investigation. Environmental

conditions also play a role; in-service infrastructure will experience temperature fluctuations from

night to day and from season to season. Water levels may also rise and fall in reality, creating

wetting and drying conditions which are known to be more detrimental to concrete corosion.

When this is combined with varying water flows, the experimental programme cannot claim to

represent each and every environmental condition that will be present over the service life of a

component. It can however, serve as an indicator in the performance of various concrete mixes

to this highly aggressive environment. While more accurate methods exist of replicating the

bacterial environment, the complexity of such an investigation is both time consuming and cost

prohibitive. The experimental programme carried out in this instance may therefore represent the

most accurate method available at minimal cost with the least constraints on time.

5.3 Ultrasonic analysis

The results obtained from the laboratory results have shown the potential for assessing the small

strain Young’s modulus of concrete. It is not clear however to what extent the technique may be

useful as the results from the early age programme and sulfuric acid deterioration tests show

small strain stiffness profiles which vary in sensitivity between test programmes. The latter tests

appear to struggle initially to register a drop in stiffness, as evidenced by concurrent cube

strengths, indicating that using the current technique in practice may not adequately reflect the

integrity of the concrete until it has entered an advanced deterioration stage. Furthermore the

practicalities of the actual test may also pose difficulties. The method relies on “through

transmission” requiring both a transmitter and receiver at either side of the concrete and while

this is achievable in a laboratory environment with 100mm cubes, positioning ultrasonic

transducers in a service environment may also pose difficulties. The method also does not take

into account the presence of steel reinforcement likely to be found in concrete wastewater

treatment plant structures further adding to the heterogeneous nature of concrete and

complicating the technique.

The shear wave detector method demonstrated potential in advancing ultrasonic non-

destructive techniques for concrete. The results showed it was possible to plot the development of

55

small strain stiffness in concrete at early ages and distinguish between the different binders used.

The method appeared less accurate however, in monitoring a loss in stiffness following exposure

to a 1% sulfuric acid solution for six months. At the same it was less clear to distinguish between

the different binders used which may possibly reflect the very harsh nature of the aggressive

solution to calcium-based cementitious materials.

56

6 CONCLUSIONS

The most important aspect of this research has been highlighting the significant differences

between sulfate attack and sulfuric acid attack. Based on the obtained data the former is clearly

an expansion dominated phenomenon with a defined point of corrosion acceleration. The latter,

however, appears to be a surface dissolution mechanism combined with an extremely destructive

/ rapid diffusion process that immediately leads to an attack on the binding capabilities of cement

This has implications with respect to the fact that current design specifications for water and

wastewater treatment facilities call for the widespread use of sulfate-resisting cement,. The

specifications fail to account for the presence of an extremely corrosive acidic environment that

can ultimately affect whole-life costs.

Furthermore, the current European EN206 standards also fail to account for pH

environments below 4 which literature has suggested is far higher than what is commonly

encountered in wastewater facilities. It has already been highlighted that there is a noticeable

change between pH 4 and pH 1 in terms of mass loss acceleration, indicating an increase in the

severity of attack.

6.1 Sodium sulfate tests

The sodium sulfate expansion tests highlighted some of the key differences between the expected

and actual deterioration mechanisms in a wastewater treatment environment. Similarities are also

noted. The experimental programme also recorded an apparent relationship between expansion

and the square-root of time with each stage characterised by a specific physical deterioration

mechanism. The main conclusions that can be drawn are thus:

• Deterioration was primarily due to bulging, spalling and warping, most likely as a result

of the formation of gypsum. This type of mechanical deterioration is not generally

expected in a wastewater environment.

• Some softening of the interior of the matrix along with a white substance confirmed this

as the most likely case. The presence of gypsum is more than likely to occur in

conjunction with biogenic sulfuric acid corrosion, unless the material is washed away.

This may cause confusion as to the nature of the attack.

• Specimens containing GGBS outperformed all other mixes regardless of the cement type.

57

• CEM II/A-L limestone cements appear to possess and inherent sulfate resisting capability

that is superior to a CEM I cement. When combined with 50% or 70% GGBS it

represented the best performing binder combination.

• 100% CEM I was the worst performing cement

All conclusions are based on findings from exposing mortar prisms to the aggressive solution.

The behaviour of concrete may differ from those observed in the mortar tests.

6.2 Sulfuric acid tests

The sulfuric acid test programme primarily indicated the inability of concrete to survive very

aggressive sulfuric acid solutions. Furthermore, a collaboration of existing data of acidic

corrosion shows that this may apply to a large variety of acids including acetic and lactic acids.

The findings show that solution pH may be a controlling force in the deterioration process. The

test programme again served to highlight both the significant differences and slight similarities

between sulfate and sulfuric acid based deterioration mechanisms. The main conclusions that can

be drawn are thus:

• Sulfuric acid deterioration visually appeared to be more surface oriented than sulfate

attack. The attack was concentrated primarily on the matrix of the cement.

• The main deterioration mechanism consisted of the formation of gypsum on the external

surfaces of the concrete specimens. This was followed by surface delamination, some

spalling. In the long term a widespread lack of cohesion leads to a failure mechanism that

spreads directly to the core.

• With reference to mass loss, there was very little distinction between the performances of

each of the six mixes. Some minor differences were, however, noted. An initial increase

(or no decrease) in mass for the first 28 days appeared to be common to all mixes and test

conditions.

• The use of brushing appeared to increase the rate of attack and the level of mass loss at

six months by a factor of approximately 1.5. It is unclear to what extent the use of

brushing replicates actual corrosion mechanisms.

58

• Mass loss may not be an accurate performance indicator of the deterioration level. Despite

a difference between the brushed and unbrushed specimens, cube strengths revealed

almost no change in performance.

• Expansion was not deemed to be an important parameter in sulfuric acid based

degradation.

• The use of GGBS appeared to have little or no effect on improving resistance. Similarly

SRPC had no effect on the performance of concrete in this environment.

• The rate of visual deterioration of a 1% solution of sulfuric acid attack greatly exceeded

that of a 5% sodium sulfate solution.

• The 1% sulfuric acid solution (pH≈1.5) represents the most severe conditions to be

expected in service. Actual pH levels may vary according to time, temperature and

bacterial activity.

• Sulfate deterioration differs from that of sulfuric acid deterioration. It may be possible

upon visual examination to confuse the two mechanisms on account of the presence of

gypsum, common to both.

6.3 Summary

The results of this investigation have clearly outlined the cause of concrete deterioration in

wastewater treatment systems. Consequently, a clear distinction has been drawn between

degradation due to sulfate attack and that due to a sulfuric acid attack in this environment. It is

evident that neither the concrete standards nor concrete specifiers are taking into account the

harsh nature of this form of attack by suitably distinguishing between the two corrosion

phenomena. The laboratory programme has also failed to highlight a concrete specification that is

capable of withstanding biodeterioration. For this to be fully addressed, the range of aggressive

environments associated with wastewater applications needs to be quantified and used as an input

for future research work.

59

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ASTM (2004) C1012 - 04 Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution.

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CHAIX, J.-F., GARNIER, V. & CORNELOUP, G. (2006) Ultrasonic wave propagation in heterogeneous solid media: Theoretical analysis and experimental validation. Ultrasonics, 44, 200-210.

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IRASSAR, E. F., BONAVETTI, V. L., TREZZA, M. A. & GONZÁLEZ, M. A. (2005) Thaumasite formation in limestone filler cements exposed to sodium sulphate solution at 20 °C. Cement and Concrete Composites, 27, 77-84.

IRASSAR, E. F., GONZÁLEZ, M. & RAHHAL, V. (2000) Sulphate resistance of type V cements with limestone filler and natural pozzolana. Cement and Concrete Composites, 22, 361-368.

LEE, H. K., LEE, K. M., KIM, Y. H., YIM, H. & BAE, D. B. (2004) Ultrasonic in-situ monitoring of setting process of high-performance concrete. Cement and Concrete Research, 34, 631-640.

MONTEIRO, P. J. M. & KURTIS, K. E. (2008) Experimental Asymptotic Analysis of Expansion of Concrete Exposed to Sulfate Attack. ACI Materials Journal, 105, 62-71.

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O'CONNELL, M., MCNALLY, C. & RICHARDSON, M.G. (2010) 'Biochemical attack on concrete in wastewater applications: a state of the art review'. Cement and Concrete Composites, 32, 479-485

O'CONNELL, M., MCNALLY, C., DONOHUE, S. & RICHARDSON, M.G. (2009) Assessment of ultrasonic signals to determine the early age properties of concretes incorporating secondary cementitious materials. In: Proceedings of the 15th European Meeting of Environmental and

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OSBORNE, G. J. (1999) Durability of Portland blast-furnace slag cement concrete. Cement and

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PAVÍA, S. & CONDREN, E. (2008) Study of the Durability of OPC versus GGBS Concrete on Exposure to Silage Effluent. Journal of Materials in Civil Engineering, 20, 313-320.

PIPILIKAKI, P., KATSIOTI, M. & GALLIAS, J. L. (2009) Performance of limestone cement mortars in a high sulfates environment. Construction and Building Materials, 23, 1042-1049.

RAMEZANIANPOUR, A. A., GHIASVAND, E., NICKSERESHT, I., MAHDIKHANI, M. & MOODI, F. (2009) Influence of various amounts of limestone powder on performance of Portland limestone cement concretes. Cement and Concrete Composites, 31, 715-720.

RAMYAR, K. & INAN, G. (2007) Sodium sulfate attack on plain and blended cements. Building

and Environment, 42, 1368-1372.

ROBEYST, N., GRUYAERT, E., GROSSE, C. U. & DE BELIE, N. (2008) Monitoring the setting of concrete containing blast-furnace slag by measuring the ultrasonic p-wave velocity. Cement and Concrete Research, 38, 1169-1176.

61

TIAN, B. & COHEN, M. D. (2000) Does gypsum formation during sulfate attack on concrete lead to expansion? Cement and Concrete Research, 30, 117-123.

TOSUN, K., FELEKOGLU, B., BARADAN, B. & AKIN ALTUN, I. (2009) Effects of limestone replacement ratio on the sulfate resistance of Portland limestone cement mortars exposed to extraordinary high sulfate concentrations. Construction and Building Materials, 23, 2534-2544.

TSIVILIS, S., TSANTILAS, J., KAKALI, G., CHANIOTAKIS, E. & SAKELLARIOU, A. (2003) The permeability of Portland limestone cement concrete. Cement and Concrete Research, 33, 1465-1471.

VOIGT, T., GROSSE, C. U., SUN, Z., SHAH, S. P. & REINHARDT, H. W. (2005) Comparison of ultrasonic wave transmission and reflection measurements with P-and S-waves on early age mortar and concrete. Materials and Structures, 38, 729-738.

APPENDIX A: Review Paper

APPENDIX C: Sodium Sulfate Expansion Data

Days ∆L (%) P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0 0.000 0.01 0.01 56 0.006 0.003 0.004 0.01 84 0.012 0.007 0.01 0.016 112 0.025 0.018 0.019 0.027 140 0.027 0.031 0.024 0.029 175 0.029 0.029 0.026 0.031 196 0.035 0.034 0.031 0.037 224 0.043 0.046 0.041 0.046 252 0.045 0.053 0.046 0.047 280 0.051 0.062 0.045 0.05 308 0.06 0.077 0.053 0.058 336 0.066 0.090 0.058 0.062 364 0.073 0.109 0.069 0.072 392 0.081 0.128 0.077 0.078 420 0.101 0.154 0.093 0.092 448 0.105 0.182 0.102 0.097 476 0.119 0.222 0.119 0.114 504 0.141 0.268 0.138 0.131

0

0.05

0.1

0.15

0.2

0.25

0.3

0 56 112 168 224 280 336 392 448 504 560

Ex

pa

nsi

on

%

Days Exposure

CEM II-A/L 100%

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.004 0.006 0.004 0.006 56 0.006 0.007 0.008 0.005 84 0.012 0.012 0.009 0.011 112 0.019 0.018 0.013 0.012 140 0.015 0.018 0.016 0.015 175 0.013 0.016 0.015 0.019 196 0.015 0.017 0.016 0.018 224 0.017 0.017 0.017 0.020 252 0.018 0.020 0.017 0.021 280 0.017 0.022 0.020 0.024 308 0.018 0.022 0.021 0.026 336 0.018 0.024 0.022 0.026 364 0.018 0.024 0.022 0.027 392 0.021 0.026 0.026 0.03 420 0.021 0.028 0.025 0.031 448 0.022 0.030 0.027 0.032 476 0.026 0.030 0.030 0.033 504 0.027 0.032 0.030 0.035

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 56 112 168 224 280 336 392 448 504 560

Ex

pa

nsi

on

%

Days Exposure

CEM II-A/L + 50% GGBS

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.005 0.002 0.008 0.005 56 0.004 0.004 0.002 0.004 84 0.008 0.010 0.012 0.012 112 0.010 0.010 0.014 0.010 140 0.013 0.015 0.016 0.014 175 0.017 0.012 0.015 0.014 196 0.02 0.014 0.017 0.016 224 0.019 0.014 0.017 0.017 252 0.022 0.017 0.020 0.019 280 0.024 0.018 0.022 0.02 308 0.026 0.021 0.023 0.025 336 0.026 0.020 0.023 0.023 364 0.026 0.021 0.024 0.024 392 0.029 0.024 0.027 0.029 420 0.028 0.026 0.027 0.027 448 0.034 0.030 0.029 0.03 476 0.033 0.030 0.031 0.032 504 0.033 0.031 0.035 0.036

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 56 112 168 224 280 336 392 448 504 560

Ex

pa

nsi

on

%

Days Exposure

CEMII-A/L + 70% GGBS

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.013 0.003 0.008 0.014 56 0.025 0.015 0.022 0.026 84 0.029 0.024 0.031 0.034 119 0.037 0.031 0.041 0.046 140 0.048 0.043 0.056 0.058 168 0.059 0.055 0.071 0.072 196 0.072 0.068 0.086 0.089 224 0.088 0.084 0.107 0.109 252 0.109 0.104 0.134 0.132 280 0.123 0.122 0.162 0.155 308 0.153 0.153 0.209 0.196 336 0.185 0.184 0.258 0.236 364 0.249 0.239 0.341 0.315 392 0.309 0.297 0.445 0.404 420 0.407 0.377 0.571 0.52 448 0.546 0.502 0.725 0.664

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 56 112 168 224 280 336 392 448 504

Ex

pa

nsi

on

%

Days Exposure

CEM I 100%

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.003 0.008 0 0.002 56 0.006 0.012 0.006 0.008 84 0.015 0.016 0.009 0.013 119 0.013 0.017 0.014 0.021 140 0.018 0.021 0.017 0.024 168 0.016 0.024 0.018 0.026 196 0.019 0.026 0.021 0.028 224 0.02 0.028 0.023 0.031 252 0.021 0.033 0.025 0.034 280 0.023 0.034 0.026 0.036 308 0.023 0.034 0.028 0.038 336 0.024 0.039 0.029 0.039 364 0.028 0.041 0.034 0.042 392 0.03 0.042 0.034 0.044 420 0.031 0.046 0.035 0.046 448 0.033 0.049 0.037 0.047

0

0.01

0.02

0.03

0.04

0.05

0.06

0 56 112 168 224 280 336 392 448 504

Ex

pa

nsi

on

%

Days Exposure

CEM I + 70% GGBS

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0 0 0 28 0 0 0 0.001 56 0 0.003 0.002 0.006 84 0.003 0.007 0.004 0.009 112 0.008 0.012 0.01 0.012 140 0.012 0.016 0.014 0.014 168 0.015 0.02 0.018 0.019 196 0.022 0.024 0.023 0.023 224 0.024 0.029 0.027 0.026 252 0.024 0.031 0.031 0.028 280 0.032 0.036 0.036 0.028 308 0.041 0.044 0.044 0.037 336 0.048 0.053 0.051 0.042 364 0.051 0.059 0.058 0.045 392 0.064 0.068 0.067 0.054 420 0.071 0.075 0.073 0.06

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 56 112 168 224 280 336 392 448

Ex

pa

nsi

on

%

Days Exposure

SRPC 100%

Prism 1

Prism 2

Prism 3

Prism 4

Results Contd: Expansion vs time 0.5

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM II 100%

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM II + 50% GGBS

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 2 4 6 8 10 12 14 16 18 20

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM II + 70% GBS

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM I 100%

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM I + 70% GGBS

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

SRPC 100%

APPENDIX D: Concrete Permeability and Sorption Tests

Air permeability results

y = -0.054x + 6.2021

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MA53

y = -0.0283x + 6.1883

5.7

5.75

5.8

5.85

5.9

5.95

6

6.05

6.1

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MA16

y = -0.0473x + 6.1426

5.4

5.5

5.6

5.7

5.8

5.9

6

0 5 10 15 20

Ln(P

ress

ure

)

Time mins)

MB15

y = -0.013x + 6.200

5.98

6

6.02

6.04

6.06

6.08

6.1

6.12

6.14

6.16

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MB16

y = -0.0555x + 6.2162

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MC15

y = -0.018x + 6.221

5.9

5.95

6

6.05

6.1

6.15

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MC16

y = -0.0738x + 6.1296

4.8

5

5.2

5.4

5.6

5.8

6

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MD15

y = -0.015x + 6.224

5.95

6

6.05

6.1

6.15

6.2

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MD16

y = -0.0345x + 6.1994

5.65

5.7

5.75

5.8

5.85

5.9

5.95

6

6.05

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

ME15

y = -0.014x + 6.235

6

6.02

6.04

6.06

6.08

6.1

6.12

6.14

6.16

6.18

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

ME16

y = -0.082x + 6.1198

4.8

5

5.2

5.4

5.6

5.8

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

SR15

y = -0.006x + 6.223

6.13

6.14

6.15

6.16

6.17

6.18

6.19

6.2

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

SR16

Water permeability results

y = 3.87E-08x + 1.23E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA53

y = 1.78E-08x - 9.05E-09

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

7E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA16

y = 2.35E-08x + 6.28E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB15

y = 1.30E-08x + 1.40E-08

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

7E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB16

y = 3.12E-08x - 2.85E-09

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC15

y = 1.96E-08x + 3.96E-08

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC16

y = 7.57E-08x + 1.96E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

3.00E-07

3.50E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD15

y = 2.68E-08x + 1.26E-08

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD16

y = 4.07E-08x + 1.49E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME15

y = 2.15E-08x - 1.58E-09

0

2E-08

4E-08

6E-08

8E-08

0.0000001

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME16

y = 6.44E-08x + 2.96E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

3.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR15

y = 2.25E-08x + 5.29E-09

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR16

Water sorptivity

y = 1.56E-08x - 6.25E-09

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA53

y = 2.27E-08x + 1.59E-08

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA16

y = 5.07E-09x + 6.55E-09

0

5E-09

1E-08

1.5E-08

2E-08

2.5E-08

3E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB15

y = 4.04E-09x + 1.76E-08

0

5E-09

1E-08

1.5E-08

2E-08

2.5E-08

3E-08

3.5E-08

4E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB16

y = 2.59E-08x - 4.23E-09

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC15

y = 1.59E-08x - 3.35E-08

0

5E-09

1E-08

1.5E-08

2E-08

2.5E-08

3E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC16

y = 3.97E-08x + 2.36E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD15

y = 1.45E-08x - 1.21E-08

0

1E-08

2E-08

3E-08

4E-08

5E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD16

y = 2.44E-08x - 2.35E-08

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

7E-08

8E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME15

y = 2.66E-08x + 5.75E-09

0.0E+00

2.0E-08

4.0E-08

6.0E-08

8.0E-08

1.0E-07

1.2E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME16

y = 5.35E-08x + 2.76E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR15

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR16

APPENDIX E: Sulfuric Acid Testing: Mass Loss Data (brushed)

MASS (g) WEEK MIX MA

CUBE No. 0 1 2 3 4 8 12 16 20 24 5 2447 2449 2448 2449 2453 15 2434 2437 2436 2435 2435 2436 16 2443 2445 2444 2443 2445 2446 2446 2447 2446 2446 6 2436 2438 2438 2439 2439 7 2449 2451 2451 2451 2455 2453 8 2448 2451 2451 2451 2452 2453 2454 2454 2454 2454 9 2453 2461 2468 2446 2442 10 2456 2464 2473 2449 2446 2357 11 2453 2462 2472 2448 2444 2344 2238 2147 2071 1999 12 2487 2511 2517 2498 2497 13 2462 2487 2493 2475 2473 2406 14 2473 2500 2502 2486 2485 2415 2318 2242 2170 2104 Prism No. 1 3549 3550 3548 3550 3544 3550 3551 3551 3550 3552 2 3535 3527 3526 3528 3528 3527 3528 3528 3529 3529 3 3572 3582 3593 3569 3570 3395 3227 3101 2996 2891 4 3596 3611 3623 3588 3582 3422 3256 3128 3018 2919

∆ MASS MIX MA

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 5 0 33 17 33 100 15 0 50 33 17 17 16 0 33 17 0 33 50 50 67 50 50 6 0 33 33 50 50 0 7 0 33 33 33 100 67 8 0 50 50 50 67 83 100 100 100 100 9 0 133 250 -117 -183 10 0 133 283 -117 -167 -1650 11 0 150 317 -83 -150 -1817 -3583 -5100 -6367 -7567 12 0 436 545 200 182 13 0 455 564 236 200 -1018 14 0 491 527 236 218 -1055 -2818 -4200 -5509 -6709 PRISM No. 1 0 12 -12 12 -58 12 23 23 12 35 2 0 -93 -104 -81 -81 -93 -81 -81 -70 -70 3 0 116 243 -35 -23 -2052 -4000 -5461 -6678 -7896 4 0 174 313 -93 -162 -2017 -3942 -5426 -6701 -7849

MASS (g) WEEK MIX MB

CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2423 2426 2426 2426 2424 4 2434 2436 2436 2437 2436 5 2421 2422 2422 2423 2422 2422 2423 2423 2423 2424 6 2424 2426 2427 2426 2425 2425 7 2423 2426 2424 2425 2425 2425 8 2436 2437 2438 2436 2437 2437 2438 2438 2438 2438 9 2445 2441 2438 2422 2411 10 2429 2425 2426 2405 2394 2273 11 2442 2440 2434 2417 2406 2281 2175 2099 2016 1956 12 2485 2484 2488 2467 2458 13 2485 2485 2487 2472 2463 2361 14 2456 2452 2455 2435 2427 2325 2238 2161 2082 2019 PRISM No. 1 3485 3486 3487 3484 3485 3485 3486 3487 3486 3487 2 3468 3470 3470 3468 3470 3470 3470 3470 3471 3473 3 3494 3483 3488 3466 3448 3281 3138 3022 2903 2814 4 3498 3496 3504 3480 3463 3303 3156 3044 2931 2845

∆ MASS MIX MB

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 50 50 50 17 4 0 33 33 50 33 5 0 17 17 33 17 17 33 33 33 50 6 0 33 50 33 17 17 7 0 50 17 33 33 33 8 0 17 33 0 17 17 33 33 33 33 9 0 -67 -117 -383 -567 10 0 -67 -50 -400 -583 -2600 11 0 -33 -133 -417 -600 -2683 -4450 -5717 -7100 -8100 12 0 -18 55 -327 -491 13 0 0 36 -236 -400 -2255 14 0 -73 -18 -382 -527 -2382 -3964 -5364 -6800 -7945 PRISM No. 1 0 12 23 -12 0 0 12 23 12 23 2 0 23 23 0 23 23 23 23 35 58 3 0 -128 -70 -325 -533 -2470 -4128 -5472 -6852 -7884 4 0 -23 70 -209 -406 -2261 -3965 -5264 -6574 -7571

MASS (g) WEEK MIX MC

CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2437 2438 2439 2438 2437 4 2434 2437 2436 2436 2435 5 2439 2441 2441 2441 2440 2441 2442 2442 2440 2442 6 2421 2424 2425 2423 2423 2424 7 2439 2440 2441 2441 2440 2441 8 2438 2440 2440 2439 2439 2439 2440 2440 2438 2441 9 2407 2404 2410 2394 2387 10 2435 2433 2439 2427 2420 2311 11 2447 2443 2451 2438 2424 2311 2205 2122 2051 1986 12 2478 2478 2485 2471 2461 13 2494 2498 2504 2491 2482 2379 14 2472 2475 2481 2470 2457 2353 2272 2198 2135 2078 PRISM No. 1 3449 3451 3452 3452 3450 3450 3452 3451 3450 3453 2 3472 3477 3476 3475 3476 3475 3476 3475 3475 3478 3 3515 3512 3520 3507 3494 3370 3228 3107 2998 2912 4 3475 3476 3486 3471 3452 3334 3193 3064 2957 2868

∆ MASS MIX MC

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 17 33 17 0 4 0 50 33 33 17 5 0 33 33 33 17 33 50 50 17 50 6 0 50 67 33 33 50 7 0 17 33 33 17 33 8 0 33 33 17 17 17 33 33 0 50 9 0 -50 50 -217 -333 10 0 -33 67 -133 -250 -2067 11 0 -67 67 -150 -383 -2267 -4033 -5417 -6600 -7683 12 0 0 127 -127 -309 13 0 73 182 -55 -218 -2091 14 0 55 164 -36 -273 -2164 -3636 -4982 -6127 -7164 PRISM No. 1 0 23 35 35 12 12 35 23 12 46 2 0 58 46 35 46 35 46 35 35 70 3 0 -35 58 -93 -243 -1681 -3328 -4730 -5994 -6991 4 0 12 128 -46 -267 -1635 -3270 -4765 -6006 -7038

MASS (g) WEEK MIX MD

CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2519 2522 2522 2521 2520 4 2516 2518 2518 2518 2517 5 2516 2519 2518 2518 2518 2518 2519 2519 2519 2518 6 2527 2529 2529 2529 2528 2529 7 2515 2517 2517 2516 2517 2517 8 2500 2504 2502 2503 2502 2503 2504 2503 2503 2502 9 2450 2435 2436 2419 2409 10 2446 2433 2434 2419 2411 2298 11 2446 2432 2432 2414 2404 2297 2191 2104 2020 1957 12 2502 2496 2497 2482 2475 13 2496 2496 2496 2481 2474 2377 14 2481 2480 2481 2468 2457 2364 2270 2199 2124 2063 PRISM No. 1 3527 3528 3530 3530 3528 3529 3531 3530 3532 3531 2 3499 3504 3505 3503 3502 3503 3503 3504 3504 3504 3 3512 3497 3497 3477 3464 3325 3174 3061 2950 2867 4 3503 3484 3489 3461 3444 3297 3136 3024 2916 2838

∆ MASS MIX MD

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 50 50 33 17 4 0 33 33 33 17 5 0 50 33 33 33 33 50 50 50 33 6 0 33 33 33 17 33 7 0 33 33 17 33 33 8 0 67 33 50 33 50 67 50 50 33 9 0 -250 -233 -517 -683 10 0 -217 -200 -450 -583 -2467 11 0 -233 -233 -533 -700 -2483 -4250 -5700 -7100 -8150 12 0 -109 -91 -364 -491 13 0 0 0 -273 -400 -2164 14 0 -18 0 -236 -436 -2127 -3836 -5127 -6491 -7600 Prism No. 1 0 12 35 35 12 23 46 35 58 46 2 0 58 70 46 35 46 46 58 58 58 3 0 -174 -174 -406 -557 -2168 -3919 -5229 -6516 -7478 4 0 -220 -162 -487 -684 -2388 -4255 -5554 -6806 -7710

MASS (g) WEEK MIX ME

CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2447 2450 2448 2448 2448 4 2437 2437 2440 2438 2438 5 2423 2424 2424 2425 2425 2425 2426 2425 2425 2426 6 2427 2427 2427 2428 2427 2428 7 2411 2412 2413 2413 2413 2413 8 2446 2449 2448 2448 2448 2448 2449 2448 2449 2449 9 2432 2432 2437 2416 2408 10 2420 2422 2425 2407 2396 2303 11 2433 2435 2440 2418 2409 2313 2210 2127 2042 1982 12 2471 2483 2486 2460 2458 13 2486 2493 2498 2481 2472 2386 14 2470 2480 2484 2464 2455 2372 2284 2215 2144 2080 PRISM No. 1 3532 3536 3537 3536 3536 3536 3536 3535 3535 3535 2 3471 3476 3476 3475 3473 3474 3475 3475 3476 3476 3 3494 3468 3492 3473 3460 3331 3198 3084 2974 2896 4 3469 3489 3478 3451 3440 3329 3199 3076 2952 2870

∆ MASS MIX ME

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 50 17 17 17 4 0 0 50 17 17 5 0 17 17 33 33 33 50 33 33 50 6 0 0 0 17 0 17 7 0 17 33 33 33 33 8 0 50 33 33 33 33 50 33 50 50 9 0 0 83 -267 -400 10 0 33 83 -217 -400 -1950 11 0 33 117 -250 -400 -2000 -3717 -5100 -6517 -7517 12 0 218 273 -200 -236 13 0 127 218 -91 -255 -1818 14 0 182 255 -109 -273 -1782 -3382 -4636 -5927 -7091 PRISM No. 1 0 46 58 46 46 46 46 35 35 35 2 0 58 58 46 23 35 46 46 58 58 3 0 -301 -23 -243 -394 -1890 -3432 -4754 -6029 -6933 4 0 232 104 -209 -336 -1623 -3130 -4557 -5994 -6945

MASS (g) WEEK MIX SR

CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2481 2482 2482 2482 2482 4 2459 2461 2462 2460 2460 2461 5 2470 2471 2472 2471 2471 2472 2472 2472 2472 2471 6 2478 2480 2479 2480 2480 7 2482 2483 2483 2483 2483 2484 8 2458 2461 2460 2460 2460 2461 2462 2461 2462 2460 9 2461 2451 2448 2431 2423 10 2478 2472 2469 2447 2437 2337 11 2464 2452 2450 2434 2425 2326 2190 2105 2028 1962 12 2520 2526 2524 2508 2500 13 2509 2514 2512 2498 2490 2415 14 2522 2530 2529 2512 2507 2421 2309 2232 2159 2092 PRISM No. 1 3543 3546 3546 3546 3545 3545 3546 3546 3547 3548 2 3550 3551 3549 3550 3550 3550 3552 3553 3553 3553 3 3542 3541 3537 3512 3504 3395 3211 3075 2965 2875 4 3555 3556 3552 3524 3514 3395 3205 3077 2968 2881

∆ MASS MIX SR

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 17 17 17 17 4 0 33 50 17 17 33 5 0 17 33 17 17 33 33 33 33 17 6 0 33 17 33 33 7 0 17 17 17 17 33 8 0 50 33 33 33 50 67 50 67 33 9 0 -167 -217 -500 -633 10 0 -100 -150 -517 -683 -2350 11 0 -200 -233 -500 -650 -2300 -4567 -5983 -7267 -8367 12 0 109 73 -218 -364 13 0 91 55 -200 -345 -1709 14 0 145 127 -182 -273 -1836 -3873 -5273 -6600 -7818 PRISM No. 1 0 35 35 35 23 23 35 35 46 58 2 0 12 -12 0 0 0 23 35 35 35 3 0 -12 -58 -348 -441 -1704 -3838 -5414 -6690 -7733 4 0 12 -35 -359 -475 -1855 -4058 -5542 -6806 -7814

Week Mass Loss (g/m2)

MA MB MC MD ME SR

0 0 0 0 0 0 0

1 261 51 6 153 66 15

2 380 25 105 137 139 55

3 29 335 107 408 198 353

4 11 513 285 567 337 483

8 1601 2442 1984 2300 1844 1959

12 3586 4127 3567 4065 3415 4084

16 5047 5454 4974 5402 4762 5553

20 6314 6832 6182 6728 6117 6841

24 7505 7875 7219 7735 7121 7933

APPENDIX F: Sulfuric Acid Testing: Mass Loss Data (unbrushed)


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2468 2473 2480 2482 2478 2406 2304 2258 2219 2188 18 2472 2477 2486 2488 2487 2426 2318 2275 2226 2201

∆ MASS MIX MA

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 91 218 255 182 -1127 -2982 -3818 -4527 -5091 18 0 91 255 291 273 -836 -2800 -3582 -4473 -4927


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2469 2484 2498 2516 2512 2390 2294 2258 2220 2213 18 2494 2511 2526 2542 2548 2409 2310 2272 2239 2230

∆ MASS MIX MB

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 273 527 855 782 -1436 -3182 -3836 -4527 -4655 18 0 309 582 873 982 -1545 -3345 -4036 -4636 -4800


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2459 2482 2496 2516 2529 2394 2299 2255 2224 2231 18 2484 2477 2517 2534 2549 2426 2329 2291 2262 2257

∆ MASS MIX MC

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 418 673 1036 1273 -1182 -2909 -3709 -4273 -4145 18 0 -127 600 909 1182 -1055 -2818 -3509 -4036 -4127


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2553 2563 2575 2580 2581 2471 2378 2331 2287 2266 18 2544 2557 2569 2580 2578 2453 2366 2325 2286 2267

∆ MASS MIX MD

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 182 400 491 509 -1491 -3182 -4036 -4836 -5218 18 0 236 455 655 618 -1655 -3236 -3982 -4691 -5036


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2478 2498 2512 2525 2534 2424 2326 2281 2258 2262 18 2483 2503 2513 2531 2541 2424 2338 2288 2260 2260

∆ MASS MIX ME

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 364 618 855 1018 -982 -2764 -3582 -4000 -3927 18 0 364 545 873 1055 -1073 -2636 -3545 -4055 -4055


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2510 2526 2540 2549 2540 2435 2337 2291 2245 2220 18 2529 2549 2556 2557 2552 2459 2351 2303 2257 2229

∆ MASS MIX SR

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24

0 291 545 709 545 -1364 -3145 -3982 -4818 -5273 0 364 491 509 418 -1273 -3236 -4109 -4945 -5455


MA MB MC MD ME SR

0 0 0 0 0 0 0

1 61 194 97 140 243 219

2 158 370 425 286 389 346

3 183 577 649 377 577 407

4 153 589 820 383 692 323

8 982 1491 1118 1573 1027 1318

12 2891 3264 2864 3209 2700 3191

16 3700 3936 3609 4009 3564 4045

20 4500 4582 4155 4764 4027 4882

24 5009 4727 4136 5127 3991 5364

APPENDIX G: Sulfuric Acid Testing: Cube Strength Data

Compressive Strength: Mix MA

Days Water Acid % Loss

0 57 57 0% 28 57 50 12% 56 58 35 40% 168 60 21 65%

Compressive Strength: Mix MB


0 61 61 0% 28 65 53 18% 56 65 35 46% 168 70 19 74%

Compressive Strength: Mix MC


0 58 58 0% 28 58 51 12% 56 63 37 42% 168 65 22 66%

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168C

ub

e s

tre

ng

th (

MP

a)

Days


Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days


Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days


Cubes in water

Cubes in acid

Compressive Strength: Mix MD


0 65 65 0% 28 71 56 21% 56 75 43 42% 168 77 19 76%

Compressive Strength: Mix ME


0 54 54 0% 28 57 49 14% 56 59 34 42% 168 69 18 74%

Compressive Strength: Mix SR


0 60 60 0% 28 58 59 0% 56 68 41 40% 168 75 21 72%

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days

MD - 100% CEM I

Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

Days


Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

Str

en

gth

(M

pa

)

Days

SR - 100% SRPC

Cubes in water

Cubes in acid

APPENDIX H: Sulfuric Acid Testing: Expansion Data

MB1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.62 3.332 Wk 0 6.634 3.517 6.717 3.42 6.732 3.601 Wk 4 5.79 2.501 0.003 Wk 4 5.814 2.661 -0.009 5.852 2.557 0.001 5.869 2.712 -0.010 Wk 8 6.454 3.158 0.000 Wk 8 6.46 3.299 -0.012 6.46 3.158 -0.002 6.46 3.304 -0.010 Wk 12 6.147 2.83 -0.008 Wk 12 6.146 3.001 -0.006 6.151 2.862 0.003 6.153 2.976 -0.018 Wk 16 6.052 2.748 -0.003 Wk 16 6.055 2.888 -0.014 6.059 2.752 -0.004 6.059 2.885 -0.017 Wk 20 6.242 2.948 0.001 Wk 20 6.246 3.082 -0.013 6.249 2.949 -0.001 6.251 3.083 -0.015 Wk 24 6.599 3.298 -0.002 Wk 24 6.606 3.435 -0.016 6.608 3.301 -0.004 6.61 3.434 -0.018 MB3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 Wk 0 6.689 3.48 6.779 3.558 Wk 4 Wk 4 5.85 2.687 0.023 5.88 2.668 0.004 Wk 8 Wk 8 6.46 3.226 -0.005 NO READINGS 6.461 -0.008 Wk 12 Wk 12 6.151 2.862 -0.027 6.081 2.823 -0.015 Wk 16 Wk 16 6.058 2.807 -0.012 6.06 2.798 -0.016 Wk 20 Wk 20 6.249 2.989 -0.016 6.252 2.992 -0.016 Wk 24 Wk 24 6.608 3.344 -0.017

6.608 3.347 -0.016 MB1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.981 2.621 Wk 0 5.956 2.75 5.989 2.625 5.994 2.761 Wk 4 6.618 3.345 0.036 Wk 4 6.664 3.422 -0.004 6.851 3.476 -0.004 6.869 3.631 -0.002 Wk 8 6.189 2.807 -0.007 Wk 8 6.19 2.942 -0.006 6.192 2.823 -0.002 6.192 2.937 -0.009 Wk 12 6.436 3.138 0.026 Wk 12 6.234 3.014 0.005 6.424 3.047 -0.005 6.448 3.209 -0.002 Wk 16 6.229 2.887 0.009 Wk 16 6.232 2.99 -0.004 6.249 2.861 -0.010 6.251 3.005 -0.005 Wk 20 6.596 3.213 -0.008 Wk 20 6.605 3.352 -0.008 6.621 3.23 -0.011 6.62 3.357 -0.012 Wk 24 6.433 3.046 -0.009 Wk 24 6.437 3.176 -0.011 6.439 3.047 -0.011 6.439 3.178 -0.011 MB3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.975 2.884 Wk 0 5.985 2.851 5.997 2.874 6 2.822 Wk 4 6.802 3.685 0.002 Wk 4 6.848 3.625 -0.018 6.882 3.725 -0.014 6.883 3.665 -0.016 Wk 8 6.191 3.031 -0.015 Wk 8 6.192 2.981 -0.013 6.192 3.039 -0.012 6.192 2.976 -0.015 Wk 12 6.258 3.22 0.034 Wk 12 6.396 3.188 -0.012 6.47 3.328 -0.008 6.484 3.246 -0.024 Wk 16 6.243 3.056 -0.026 Wk 16 6.245 3.013 -0.022 6.252 3.082 -0.019 6.254 3.019 -0.023 Wk 20 6.61 3.427 -0.024 Wk 20 6.624 3.354 -0.037 6.621 3.424 -0.030 6.618 3.372 -0.027 Wk 24 6.438 3.311 -0.002 Wk 24 6.438 3.177 -0.033 6.438 3.222 -0.037 6.431 3.171 -0.033

MC1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MC2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.135 3.182 Wk 0 6.134 3.085 6.132 3.172 6.133 3.076

Wk 4 6.034 3.07 -0.002 Wk 4 6.035 2.885 -0.037 6.038 3.064 -0.006 6.039 2.893 -0.036

Wk 8 6.214 3.224 -0.012 Wk 8 6.212 3.157 0.001 6.244 3.277 -0.003 6.247 3.142 -0.019

Wk 12 6.05 3.075 -0.006 Wk 12 6.057 2.895 -0.042 6.058 3.075 -0.009 6.059 2.833 -0.068

Wk 16 6.25 3.276 -0.006 Wk 16 6.25 3.027 -0.066 6.248 3.273 -0.006 6.252 3.045 -0.060

Wk 20 6.612 3.635 -0.007 Wk 20 6.612 3.386 -0.068 6.62 3.635 -0.010 6.619 3.381 -0.072

Wk 24 6.434 3.451 -0.009 Wk 24 6.435 3.203 -0.070 6.434 3.451 -0.009 6.436 3.202 -0.071

MC3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MC4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.133 2.949 Wk 0 6.132 3.017 6.133 2.951 6.132 2.881

Wk 4 6.035 2.833 -0.007 Wk 4 6.033 2.721 -0.024 6.039 2.83 -0.010 6.039 2.724 -0.026

Wk 8 6.233 3.07 0.008 Wk 8 6.241 2.959 -0.012 6.247 3.037 -0.010 6.247 2.93 -0.026

Wk 12 6.058 2.829 -0.018 Wk 12 6.054 2.74 -0.025 6.056 2.831 -0.016 6.059 2.73 -0.031

Wk 16 6.251 3.015 -0.021 Wk 16 6.244 2.917 -0.030 6.253 3.016 -0.021 6.251 2.918 -0.033

Wk 20 6.614 3.385 -0.018 Wk 20 6.616 3.386 0.008 6.619 3.379 -0.022 6.62 3.29 -0.032

Wk 24 6.437 3.196 -0.023 Wk 24 6.433 3.088 -0.038 6.438 3.194 -0.024 6.437 3.091 -0.038

MD1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MD2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.147 3.134 Wk 0 6.152 2.98 6.15 3.1 6.15 2.966

Wk 4 6.463 3.374 -0.016 Wk 4 6.466 3.298 0.006 6.468 3.396 -0.009 6.466 3.274 -0.003

Wk 8 6.242 3.141 -0.020 Wk 8 6.246 3.219 0.063 6.249 3.145 -0.022 6.25 3.108 0.017

Wk 12 6.054 2.951 -0.021 Wk 12 6.055 2.98 0.044 6.056 2.953 -0.021 6.057 2.884 0.004

Wk 16 6.249 3.145 -0.022 Wk 16 6.25 3.114 0.019 6.253 3.148 -0.022 6.255 3.07 0.000

Wk 20 6.61 3.502 -0.023 Wk 20 6.611 3.432 0.002 6.612 3.495 -0.027 6.612 3.427 0.000

Wk 24 6.444 3.32 -0.030 Wk 24 6.443 2.253 -0.402 6.446 3.323 -0.029 6.446 3.254 -0.003

MD3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MD4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.149 3.042 Wk 0 6.151 3.132 6.15 3.013 6.15 3.162

Wk 4 6.466 3.235 -0.038 Wk 4 6.464 3.402 -0.017 6.464 3.226 -0.040 6.464 3.399 -0.018

Wk 8 6.248 2.995 -0.046 Wk 8 6.246 3.172 -0.022 6.25 3.01 -0.041 6.25 3.163 -0.027

Wk 12 6.056 2.8 -0.048 Wk 12 6.054 2.984 -0.020 6.059 2.803 -0.048 6.056 2.969 -0.027

Wk 16 6.252 2.986 -0.052 Wk 16 6.253 3.169 -0.026 6.255 2.982 -0.054 6.257 3.162 -0.030

Wk 20 6.611 3.338 -0.054 Wk 20 6.611 3.514 -0.031 6.612 3.331 -0.058 6.611 3.517 -0.030

Wk 24 6.443 3.151 -0.062 Wk 24 6.444 3.334 -0.036 6.446 3.153 -0.062 6.447 3.334 -0.038

ME1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

ME2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.962 2.717 Wk 0 5.964 2.876 5.819 2.559 5.825 2.732

Wk 4 6.464 3.215 0.004 Wk 4 6.466 3.372 0.000 6.444 3.187 0.001 6.434 3.337 -0.002

Wk 8 6.148 2.891 0.001 Wk 8 6.152 3.047 -0.005 6.153 2.883 -0.004 6.153 3.043 -0.007

Wk 12 6.049 2.794 0.002 Wk 12 6.051 2.995 0.015 6.053 2.794 0.000 6.055 2.959 -0.001

Wk 16 6.253 2.989 -0.002 Wk 16 6.253 3.148 -0.005 6.254 2.985 -0.004 6.254 3.147 -0.006

Wk 20 6.614 3.348 -0.002 Wk 20 6.615 3.508 -0.006 6.616 3.347 -0.004 6.616 3.506 -0.007

Wk 24 6.44 3.174 -0.002 Wk 24 6.441 3.332 -0.006 6.443 3.174 -0.004 6.442 3.33 -0.008

ME3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

ME4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.964 2.662 Wk 0 5.797 2.582 5.716 2.574 5.732 2.51

Wk 4 6.467 3.209 0.018 Wk 4 6.466 3.254 0.004 6.46 3.259 0.040 6.466 3.257 0.005

Wk 8 6.153 2.988 0.055 Wk 8 6.151 2.893 -0.014 6.153 2.981 0.052 6.153 2.907 -0.010

Wk 12 6.052 2.882 0.053 Wk 12 6.054 2.787 -0.018 6.054 2.87 0.047 6.055 2.789 -0.018

Wk 16 6.253 3.075 0.050 Wk 16 6.25 2.982 -0.018 6.254 3.062 0.044 6.257 2.981 -0.022

Wk 20 6.615 3.405 0.037 Wk 20 6.615 3.34 -0.021 6.616 3.402 0.035 6.616 3.339 -0.022

Wk 24 6.443 3.222 0.032 Wk 24 6.442 3.158 -0.025 6.443 3.213 0.029 6.443 3.156 -0.026

SR1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

SR2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.683 2.672 Wk 0 5.927 2.592 5.955 2.889 5.955 2.631

Wk 4 6.458 3.224 -0.067 Wk 4 6.461 3.131 0.002 6.464 3.185 -0.085 6.46 3.083 -0.017

Wk 8 6.146 2.869 -0.084 Wk 8 6.15 2.817 0.001 6.15 2.853 -0.092 6.152 2.758 -0.024

Wk 12 6.054 2.748 -0.096 Wk 12 6.055 2.711 -0.004 6.054 2.743 -0.098 6.058 2.678 -0.018

Wk 16 6.255 2.942 -0.099 Wk 16 6.255 2.875 -0.018 6.229 2.905 -0.103 6.236 2.841 -0.024

Wk 20 6.609 3.297 -0.098 Wk 20 6.61 3.222 -0.021 6.61 3.297 -0.099 6.608 3.213 -0.024

Wk 24 6.442 3.123 -0.101 Wk 24 6.444 3.045 -0.026 6.445 3.119 -0.104 6.445 3.044 -0.026

SR3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

SR4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.937 2.681 Wk 0 5.95 2.715 5.956 2.689 5.957 2.72

Wk 4 6.463 3.129 -0.027 Wk 4 6.462 3.162 -0.025 6.465 3.119 -0.032 6.461 3.156 -0.027

Wk 8 6.15 2.806 -0.031 Wk 8 6.151 2.827 -0.035 6.149 2.804 -0.031 6.154 2.825 -0.037

Wk 12 6.058 2.696 -0.038 Wk 12 6.059 2.734 -0.035 6.056 2.69 -0.040 6.058 2.718 -0.041

Wk 16 6.255 2.893 -0.038 Wk 16 6.255 2.88 -0.055 6.239 2.87 -0.041 6.245 2.923 -0.034

Wk 20 6.611 3.226 -0.047 Wk 20 6.61 3.246 -0.051 6.597 3.201 -0.052 6.6 3.228 -0.054

Wk 24 6.444 3.053 -0.050 Wk 24 6.444 3.067 -0.056 6.445 3.047 -0.052 6.446 3.061 -0.059

Biochemical attack on concrete in wastewater applications: A state of the art review

M. O’Connell, C. McNally *, M.G. RichardsonSchool of Architecture, Landscape and Civil Engineering, University College Dublin, Newstead, Belfield, Dublin 4, Ireland

a r t i c l e i n f o

Article history:Received 14 July 2009Received in revised form 20 April 2010Accepted 1 May 2010Available online 7 May 2010

Keywords:Sulfate attackSulfuric acidThiobacillusSecondary cementitious materialsPerformance specifications

a b s t r a c t

The costs associated with the provision and maintenance of drinking water and wastewater infrastruc-ture represents a significant financial demand worldwide. Maintenance costs are disproportionately high,indicating a lack of adequate durability. There remains a lack of consensus on degradation mechanisms,the performance of various cement types, the role of bacteria in the corrosion process associated withwastewater applications and testing methodologies. This paper presents a review of the literature, out-lining the various research approaches undertaken in an effort to address this problem. The findings ofthese varying approaches are compared, and the different strategies employed are compiled and dis-cussed. It is proposed that a key step in advancing the understanding of the associated deteriorationmechanism is a combined approach that considers the interaction between biological and chemical pro-cesses. If this can be achieved then steps can be taken to establishing a performance-based approach forspecifying concrete in these harsh service conditions.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

The provision of high quality water and wastewater infrastruc-ture requires significant international expenditure on concretewith consequent expectations of lengthy service lives. For examplein the US alone, it is estimated that annual investments of up to$20 billion and $21 billion is required to provide adequateinfrastructure for drinking water and wastewater respectively[1]. It is also estimated that the annual operation and maintenancecosts associated with drinking water and wastewater infrastruc-ture to be in excess of $31 billion and $25 billion respectively.Against this backdrop, it is surprising to note that the corrosionof water and wastewater infrastructure has been a topic of debatefor decades, with little consensus on the methods for designing andspecifying this infrastructure to optimally meet the harsh environ-mental demands it will meet in service [2–7]. The majority of stud-ies to date have focused on the deterioration of concrete in sewersystems and pipelines [5,8,9]. However little detailed research hasbeen conducted into the effect of corrosion on the vital treatmentfacilities that are processing our wastewater. Concrete pipes insewer systems tend to be an ‘‘off-the-shelf” product with little in-put by the specifier into specification of mix design. As a result theperformance of the product is largely dependent on the manufac-turer’s mix design which is influenced by local factors. In treatmentplants the concrete may be specified by the engineer, but a lack ofin-depth research into the deterioration of these structures has

meant little change in professional practice concerning concretemix design.

Existing evidence has shown that corrosion is present in manyconcrete structures associated with water and wastewater treat-ment. The alarming fact is that some of these facilities are deterio-rating significantly after less than a decade in service (Fig. 1). Inthis context it is clear that current design practices based on pre-scriptive approaches to concrete specification may not be appro-priate to deal with the aggressive nature of wastewater, and insome cases, the treatment processes involved in drinking waterpurification [10]. Existing research findings are not yet influencingcurrent construction practice. The lack of widely quoted durabilitydesign formulae illustrates that the deterioration mechanismsassociated with this critical infrastructural application are not yetwidely accepted or understood. This paper will assist in bridgingthis gap by considering the role of key parameters such as environ-mental conditions, the nature of the attack and the physical resultsof the attack on the concrete. This will promote increased under-standing of the deterioration mechanism and facilitate the intro-duction of a performance-based design approach.

2. Characterising the wastewater environment

The deterioration of sewer systems has long been a topic underconsiderable scrutiny and in the mid 1940s a comprehensive scien-tific evaluation was undertaken in an attempt to understand thecorrosion process [11]. Current research has continued to focuson the deterioration of concrete sewer pipes and case studies havetaken place throughout the world, including comprehensive

0958-9465/$ - see front matter � 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.cemconcomp.2010.05.001

* Corresponding author. Tel.: +353 1 716 3202; fax: +353 1 716 3297.E-mail address: [email protected] (C. McNally).

Cement & Concrete Composites 32 (2010) 479–485

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reviews on current infrastructure [8]. In the latter, the condition ofthe sewer system in four cities in the Lebanon was evaluatedwhereby certain contributory factors in corrosion were outlined:Biological Oxygen Demand (BOD) levels, high sulfate and dissolvedsulfide concentration, high temperatures, high H2S gas concentra-tion, high turbulence and long detention times, low dissolved oxy-gen levels, low water velocity and low wastewater pH. These andother criteria have been outlined in several publications, all ofwhich detail the conditions leading to corrosion in sewer environ-ments [4,5,12–14].

The contributory factors outlined above are not only limited tosewer piping – they are also found in wastewater treatment plants.Occurrences of concrete degradation in these structures have beenrecorded in a limited fashion in aeration tanks [15], in septic tanksand pumping stations [16] and the underside of concrete slabs andin primary influent channels [17]. The latter two sources bothmake reference to the fact that corrosion has been observed justabove the waterline. This is significant in that prior experimentalresearch [5,18] into understanding degradation of concrete in sew-er pipes has proven that optimum corrosion levels also occur justabove the waterline. Work carried out into determining depth pro-files of sulfate ingress into concrete noted that core samples weretaken from the walls surrounding the spiral pump of a sewagetreatment plant as well as the concrete walls of a clarifier whichhas been damaged by sulfates originating from the sewage waters[19].

Evidence thus far has identified bacterial manifestation of thegenus ‘Thiobacillus’ as a major contributor to the deterioration pro-cess of concrete sewer pipelines [5,11]. The product of their metab-olism results in sulfuric acid being formed which attacks thecementitious matrix of the concrete causing loss of strength andcohesion. Thiobacillus however, plays only a part of a much broaderand complicated corrosion process. In the often anaerobic condi-tions which develop in raw sewage influent, sulfate-reducing bac-teria convert sulfates into sulfides such as hydrogen sulfide (H2S)gas. In favourable conditions this diffuses into the atmosphereand, in the presence of oxygen, is further reduced to elemental sul-fur or partially reduced sulfur compounds. In turn, they provide thecatalyst necessary for the aerobic Thiobacillus bacteria to begin pro-ducing sulfuric acid; a more detailed explanation of the corrosionprocess is presented in a subsequent section.

Sulfuric acid has been identified as a corrosive agent not only incorroding sewers but also in wastewater treatment plants [20,21].An attack by sulfuric acid however is a combined acid–sulfate reac-tion with the hydrogen ion causing a dissolution effect, coupledwith corrosive role played by the sulfate ion [2,22]. When sulfuric

acid reacts with a cement matrix, the first step involves a reactionbetween the acid and the calcium hydroxide (Ca(OH)2) formingcalcium sulfate according to the following equation:

CaðOHÞ2 þH2SO4 ! CaSO4 þ 2H2O ð1Þ

This is subsequently hydrated to form gypsum (CaSO4�2H2O),the appearance of which on the surface of concrete pipes takesthe form of a white, mushy substance which has no cohesive prop-erties and has, ‘‘the consistency of cottage cheese” [23]. In thecontinuing attack, the gypsum would react with the calcium alu-minate hydrate (C3A) to form ettringite, an expansive product:

3CaSO4�2H2Oþ 3CaO�Al2O3 þ 26H2O

! ðCaOÞ3�ðAl2O3Þ�ðCaSO4Þ3�32H2O ð2Þ

According to Skalny et al. [22], the ettringite can be located indeeper sections of concrete as long as the pH is high enough forit to form and the gypsum can migrate into these regions. The evi-dence gathered by Davis et al. [23] in their analysis of piping, how-ever, showed that little ettringite was discovered in the corrodingfront and that the thermodynamics of the conversion to gypsummay be so fast that ettringite is a short-lived intermediate.

From the evidence discussed above there seems to be a distinctrelationship between the corrosion occurring in concrete sewersand that in wastewater treatment facilities. Common variables in-clude environmental conditions, the nature of the attack and thephysical results of the attack on the concrete. Mehta and Burrows[24] have discussed how a paradigm shift is required in concretedesign, moving away from the traditional prescriptive approachto one that promotes a performance-based design. However forsuch an approach to succeed, it is imperative that the deteriorationmechanism is fully understood. In this light it is necessary to ac-count for the severe environments that wastewater infrastructureswill encounter in service, and to take an in-depth look at the cur-rent state of research into sulfate and sulfuric acid corrosion in awastewater environment.

3. Biodegradation aspects

3.1. Providing resistance to biochemical attack

When assessing the available scientific research, it is importantto consider sulfate attack, sulfuric acid attack and how they areboth relevant in determining the resistance of current concrete de-sign specifications to such attacks as biogenic sulfuric acid (BSA)corrosion. As expected there is much conflicting data available onthe subject, a scenario which is eloquently detailed in one practic-ing engineer’s publication on the topic [6]. Also of interest is theperformance of cements containing additions of ground granulatedblast-furnace slag (GGBS) which, when mixed with Portland ce-ment, has been proven to possess an inherent sulfate resistingcapability [25,26]. GGBS is being used in increasing quantities inconcrete practice today along with other secondary cementitiousmaterials (SCMs) such as pulverised fuel ash (PFA). With the highCO2 emissions associated with the production of Portland cement,these SCMs have the advantage of being by-products from otherindustrial processes and as such can help reduce the CO2 footprintof a construction project. While concretes produced using thesebinders are more dense and durable in the long term, they are alsoprone to reduced early age strengths and require particular atten-tion when curing [27–29].

In assessing experimental test methods previously used byresearchers many contrasting opinions exist [4,30], including theproposed inadequacy of sulfate testing as a method to analyse bio-logical corrosion in a wastewater environment while others stipu-late simultaneous biological and chemical sulfuric acid testing as

Fig. 1. Evidence of corrosion in grit removal tanks with gypsum and exposedaggregate visible above the water line in a wastewater treatment plant constructedin 2003.

480 M. O’Connell et al. / Cement & Concrete Composites 32 (2010) 479–485

the only true methodology [4]. The participation of the sulfate ionin sulfuric acid (H2SO4) corrosion and that of residual sulfates pres-ent in wastewater (found in effluent from food and beverageindustries [31]) cannot be ignored however. Reviewing in situand simulated experimental test methods also provides a valuableinsight into the aggressive nature of the environment that sewersand wastewater treatment plants are exposed to. This also helpsto characterise the environmental conditions favourable to theinitiation of biogenic sulfuric acid corrosion, allowing scope forinvestigating the role played by both sulfate-reducing and sulfur-oxidising bacteria.

3.2. Sulfate-reducing bacteria

Initiating the bacterial processes, sulfates present in the rawsewage in sewer system are converted into sulfides by sulfate-reducing anaerobic bacteria such as Desulfovibrio [4]. In partiallyfilled sewers, anaerobic conditions can only occur in the slimelayer on the walls of the pipe above the water line. Some of theessential environmental conditions necessary in the wastewaterenvironment for these bacteria to function and grow are dissolvedoxygen levels approaching zero and sufficient carbon and sulfateconcentrations in the wastewater itself [32]. When this occurs theyutilise the sulfates present in the wastewater to obtain the oxygenthey require and in turn release sulfur ions [33]. According to re-search aimed at quantifying microbial-induced deterioration ofconcrete, the bacteria derive the energy required for the reductionof sulfate by the oxidation of organic compounds and H2 [14]. Intheir assessment of Lebanon’s sewer network, Ayoub et al. [8]claim that sulfate to sulfide reduction takes place when the bacte-ria derive their oxygen from dissolved oxygen and nitrates in thewastewater. They state however, that corrosion in Lebanon’s sew-ers was not observed to have occurred in areas where dissolvedoxygen levels were greater than zero. If sulfate-reducing bacteriarequire dissolved oxygen to induce the corrosion cycle, as they sug-gest, one must ask why is it that no corrosion was found where dis-solved oxygen exists. Their own search of existing literaturesuggested that sulfide build-up could not occur with dissolved oxy-gen levels greater than 0.5 mg/l whereas Hewayde et al. [33] set alevel of 0.1 mg/l above which corrosion will not occur.

The final process in the initial stage of concrete deterioration in-volves the sulfur ions released by the bacteria. These in turn reactwith dissolved hydrogen in the wastewater to form an essentialcontributory product in the corrosion process, hydrogen sulfide(H2S) [33]. The hydrogen sulfide initially formed is found in its dis-solved liquid form but for this poorly soluble compound to contrib-ute to the concrete deterioration process it must leave thewastewater and enter a gaseous phase. The normal pH of sewageis slightly acidic and in the range pH 5–6 but when this begins tolower in conjunction with turbulent water (often found in sewerpipes or associated with some wastewater treatment processes),the H2S escapes and collects in the atmosphere above the water le-vel [4,16,33]. A thin layer of moisture exists on the surface of theconcrete pipe exposed to the atmosphere and it is into here thehydrogen sulfide is gas is dissolved. The condensate layer has ahigh pH attributed to the alkalinity of the concrete (which can havea pH of between 11 and 13). It also serves as the driving force be-hind the gas’ dissolution. At high pH levels the hydrogen sulfide isseparated into HS� or S2� ions which attract more H2S into themoisture layer [14]. Research has also shown that the concentra-tion of H2S in the moisture film increases as the pH of the mortarlining of the concrete pipe decreases [13]. In the presence of oxy-gen the H2S reacts to form elemental sulfur or partially oxidisedsulfur species [4,9,14,21], which can sometimes be seen in the cor-rosion products deposited on the concrete surface [18].

3.3. Sulfur-oxidising bacteria

The formation of sulfur is perhaps the critical link in the chain ofevents leading to the corrosion of concrete in a wastewater envi-ronment. In microbiological experiments carried out in 1945 toinvestigate why sewer pipes were corroding, Parker [11] discov-ered five strains of the species Thiobacillus on the surface of con-crete which oxidise sulfur, or some partially reduced form ofsulfur, to form sulfuric acid. More recent research suggests someof the Thiobacillus strains involved in concrete corrosion as beingThiobacillus thiooxidans, Thiobacillus intermedius, Thiobacillus pero-metabolis, Thiobacillus novellus, Thiobacillus thioparus, Thiobacillusneapolitanus and Thiobacillus versutus all of which are known to oxi-dize and grow with reduced inorganic sulfur compounds [14,34].Research has also identified iron-oxidising bacteria, such as Thioba-cillus ferrooxidans, as being involved in the production of sulfuricacid in pyritic ground and in sewage treatment plants [35,36].

Bacteria of the genus Thiobacillus do not attach themselves tothe surface of concrete under any conditions. Roberts et al. [14]state that the pH of the concrete has to be reduced to 9 and assum-ing sufficient moisture, nutrients and oxygen are present only thenwill the Thiobacillus bacteria colonise. Several theories for the low-ering of the pH of the concrete to around 9 have been put forward,including the involvement of the dissociation process of hydrogensulfide as discussed above. However the most widely assumed the-ory is that the pH will be lowered due to the effects of carbonation[13,14,23]. As a result of in situ tests conducted in a sewage systemwith high concentrations of hydrogen sulfide (>600 ppm) an alter-native theory has been put forward into determining the condi-tions necessary for bacterial colonisation [7]. The authors claimthat the generally accepted role of carbonation in lowering thepH of a concrete’s surface does not hold for their experiments. In-stead they theorise that in the thin moisture layer itself, the bacte-ria oxidise the hydrogen sulfide gas to form sulfuric acid, therebyreducing its pH. They further claim that the bacteria will grow inthe layer even when the pH of the concrete itself ranges from pH11–13. Parker [37] noted in his experimental observations how-ever, that Thiobacillus concretivorus (as he termed the strain of Thio-bacillus found to attack concrete) did not convert the hydrogensulfide directly into sulfuric acid but only free sulfur or other formsof utilisable sulfur compounds including thiosulfate [38]. In char-acterising the strain T. thiooxidans, Waksman and Joffe [39] andNica et al. [38] also stated that hydrogen sulfide and other sulfidesare not used directly by the sulfur-oxidising organism.

In recognising the wide range of Thiobacillus strains that takepart in sulfuric acid production, it must be noted that not all thrivein an identical environment. Some of these strains are categorisedinto ‘acid-preferring’ acidophilic sulfur-oxidising microorganisms(ASOM), such as T. thiooxidans and ‘neutral-preferring’ neutrophilicsulfur-oxidising microorganisms (NSOM), such as T. intermedius[14,38]. It is proposed that different strains of neutrophilic bacteriacolonise the surface of the concrete as its pH depresses fromapproximately a value of 8 to around a value of 6 through theirproduction of sulfuric acid [23]. It was also found that microbialsuccession is a surface phenomenon and that the ASOM move intothe corroding concrete with the corroding layer whereas NSOM donot.

Parker [11] observed that the bacteria which he was cultivatingsurvived to a pH of approximately 6.5 above which none was capa-ble of growth. At these slightly acidic pH values the acidophilic sul-fur-oxidising bacteria colonise and further depress the pH of theconcrete surface to as low as 2 at which level the strain T. thioox-idans can be found thriving [18,40]. The optimum temperature atwhich the acid was produced in its highest quantities after 50 dayswas found to be 30 �C while Barbosa et al. [15] noted in their re-search that ‘sulfide oxidation’ by the strain T. dentrificans decreased

M. O’Connell et al. / Cement & Concrete Composites 32 (2010) 479–485 481

at low temperature and was inhibited at 15.6 �C. Parker [11] alsodiscovered that the rate of acid production in his bacteria increasedwith increasing nitrogen levels up to a concentration of 50 ppm,above which there appeared to be a slight inhibition.

3.4. Other acids and organisms

In a departure from the accepted role of the species Thiobacillusin lowering the surface pH of concrete from approximately 8 to 4,some authors have also attributed the initial reduction to that offungus growth [5,41]. Mori et al. [5] found an unidentified greenfungus which grew at high pH levels and was capable of reducingthe pH to levels suitable for colonisation and growth of T. thiooxi-dans. Gu et al. [41] go further in their explanation and identifiedthe fungus they observed as Fusarium. They claim that this has amore detrimental effect on the concrete that that of the neutro-philic bacteria T. intermedius. In their research they described thelatter as being able to etch the surface of the concrete while thefungus Fusarium was able to penetrate the material. They also statethat a wide range of acids are produced by fungi including acetic,oxalic and glucuronic acids. A further set of experiments [42] usingmortar inoculated with bacteria including T. intermedius was con-ducted independently of Mori et al. [5]. In these experiments thedeterioration of concrete was thought to be caused by the sulfuricacid produced by the bacteria; however the authors noted littlegypsum and limited change in the sulfate ion concentration ofthe culture medium. They concluded that primary deteriorationof the concrete was caused by carbonic and organic acids, whichinclude acetic acid which are all metabolites produced by bacteria.

4. The role of biogenic sulfuric acid corrosion

4.1. Attack mechanisms

Only limited work has been carried out in assessing the perfor-mance of concrete mixes in a biological environment [4] a surpris-ing fact considering several researchers have claimed that biogenicsulfuric acid corrosion found in wastewater systems is more severethan chemical sulfuric acid and sulfate attack [43,44]. This repre-sents a key knowledge gap in the development of a material basedperformance specification. While research has identified gypsum,ettringite and even thaumasite as the end-product of the corrosionproduct the debate centres on the order of their formation, theirquantities and specific effects on the cement matrix.

The corrosive nature of a sulfuric acid attack has been well doc-umented from both in situ observations and chemical testing onconcrete [4,5,22,30,45–47]. The dissolution effect of the hydrogenion and the separate effect of the sulfate ion combine to createan aggressive set of chemical reactions, threatening the stabilityof a cement matrix. Debate exists however regarding the mecha-nisms behind chemical and biological sulfuric acid attacks, andresistance to the former does not necessarily result in resistanceto the latter [4,9,48]. Explanations centre on the involvement ofthe sulfuric acid producing bacteria Thiobacillus where Montenyet al. [4] claim that it is the moist conditions in the gypsum corro-sion front that constitute an excellent breeding ground for the bac-teria to thrive. They then migrate into the concrete producing acidmuch closer to the corrosion front although Yamanka et al. [7] dis-pute this claiming it is the acid itself moving inward. In a chemicalattack however, the poor penetration of sulfuric acid limits the ef-fects of corrosion to the surface [49]. The acid must negotiate itsway through this corrosion layer in order for the attack to con-tinue. It is generally assumed that this results in less severe conse-quences relative to a biological attack, as the corroded surface actsas a barrier for further penetration. Hence regular brushing of

loosely adhering particles may be important in any attempt to mi-mic biological activity with chemical testing [4,50].

4.2. Types of sulfuric acid attack

In 1945, C.D. Parker described a sulfuric acid attack on concretesewers as producing a white putty-like deposit, moist, flaky andeasily removed from the surface [11,37]. The calcium sulfate (gyp-sum) formed was a result of a reaction between the hydration prod-ucts in the cement matrix and the sulfuric acid [22], as previouslydescribed in Eq. (1). Experimental and in situ analysis of both mor-tar and concrete has confirmed that gypsum formation is one of theprimary corrosion mechanisms involved in the deterioration of thecement matrix leading to a loss of cohesion in cementitious calciumcompounds [5,23,33,51]. The degradation of concrete foundationsof an Italian building exposed to sewage waters however wasattributed to the growth of gypsum crystals at the aggregate-pasteinterface causing a loss of strength [52]. The build-up of gypsumthough can also act as a barrier to further penetration, slowing anattack [4,53] however it has also been claimed that the rougher sur-face area leads to a greater surface area to be attacked [18].

The relative resistance of various binder combinations to sulfu-ric acid attack has been discussed by some researchers. Experi-ments exposing 100 mm Portland cement concrete cubes with abinder of 35% ordinary Portland cement (OPC)/65% GGBS to anH2SO4 solution for 5 months, as described in BRE Digest 363 [54],reported higher performance than for binders of 100% sulfateresisting Portland cement (SRPC) or 75% OPC/25% PFA [47]. Thisimproved performance of concrete in acidic conditions has beenattributed to either lower porosity, lower levels of calcium hydrox-ide or both [4,45,48] while Saricimen et al. [16] determined that ina 3% flowing H2SO4 solution neither SRPC nor OPC showed any dif-ference in resisting attack, a conclusion supported by [7]. Montenyet al. [43] suggest that a refined pore structure will increase thecapillary action of the cement matrix and act as a mechanism forthe aggressive solution to find its way deeper into the concrete.

In experiments to assess commercially available piping, De Be-lie et al. [9] prepared non-standard cylindrical specimens of con-crete with CEM I and CEM III high sulfate resisting cement andexposed them to a 0.5% H2SO4 solution in alternating wet/dry cy-cles. They concluded the limestone aggregate, acting as a sacrificialmedium to reduce the rate of acid attack, played a more crucialrole against attack that the cement type. The sulfate resisting ce-ments also performed better than the blast-furnace slag cements,an observation similarly supported by other experimental results[29] (conducting experiments with 60% GGBS cylinders in a 1%H2SO4 for 168 days). This is however contradicted by research fromMonteny et al. [4] who performed experiments in 1–5% H2SO4

solutions. However it is noteworthy that the significance of the roleplayed by the limestone aggregate has been emphasised [25,29].

Ettringite is a crystalline compound and its formation can beobserved in the process of cement hydration (primary ettringite)and in the effects of an external sulfate attack (secondary ettring-ite). Some of the reactions associated with its formation involvecalcium aluminates, such as C3A, and gypsum but may also incor-porate an external sulfate attack on the calcium aluminate hy-drates and monosulfate hydrate phases [4,54]. According toSkalny et al. [22] under sulfuric acid attack only limited amountsof ettringite will form in deeper sections of the concrete as longas the pH is high enough to maintain its stability and enough ofthe gypsum formed in the initial stages of attack can move intothe concrete. This assessment concurs with other researcherswho have also stated ettringite’s inability to survive in an acidicenvironment [44] and even in alkaline environments with pH’sas high as 10.6 [49]. In contrast, Monteny et al. [4] stress in theirassessments the importance of ettringite and its more devastating


effect on concrete than gypsum, while its formation from a sulfuricacid attack was also documented by others assessing the influenceof fungi on concrete corrosion [42] and simulated biogenic sulfuricacid corrosion [5].

It is noteworthy that the presence of such key compounds suchas gypsum and ettringite is accepted as being a function of mix de-sign and the binder combinations used. However the notion ofusing this material design to control the presence of these expan-sive compounds is not at this stage well developed.

4.3. Influence of the sulfate ion

As an attack by sulfuric acid is a combined acid–sulfate reaction,many researchers have deemed it prudent to assess concrete sus-ceptibility in standard sulfate testing solutions including sodiumsulfate (Na2SO4), magnesium sulfate (MgSO4) or a combination ofboth. The validity of this method to assess attack in a wastewaterenvironment has however drawn some uncertainty based on dis-crepancies in chemical and biological tests [4].

Sodium and magnesium-based sulfate solutions have substan-tially different effects on concrete. With the former, calciumhydroxide primarily undergoes decomposition to gypsum and sub-sequently ettringite. When there is an insufficient source of cal-cium for the reaction to continue only then will the solutionbegin to attack the C–S–H phase [22,51]. Magnesium solutions at-tack all phases simultaneously in the cement matrix preferring cal-cium hydroxide first followed by the calcium–silicate–hydrate (C–S–H) phase to obtain its reactive calcium. The products from amagnesium sulfate reaction include gypsum, ettringite, a magne-sium–silicate–hydrate (which lacks cohesive properties) and themineral form of magnesium hydroxide, brucite [55].

In sodium sulfate, ettringite can be associated mainly with thereaction between the AFm monosulfate phase and the sulfate ionsmigrating into the concrete. At low concentrations of sulfate solu-tions (<1000 mg SO2�

4 /l) ettringite will be the primary cause ofdeterioration [4] whereas at higher concentrations (>8000 mgSO2�

4 /l) gypsum will dominate in a sulfate attack [56]. It is impor-tant, therefore, to use a concentration of sulfates that accuratelyrepresents the corrosion mechanism in the desired environment.

In magnesium sulfate solutions the deterioration mechanism isprimarily a result of the loss of cohesion and disintegration withthe formation of gypsum and magnesium hydroxide [4,22]. Thesaturated solution pH of magnesium hydroxide is approximately10.5 and consequently this causes the destabilisation of ettringite.As a result the circumstances favourable in the formation ofettringite from a magnesium sulfate attack are significantly im-peded [57]. Skalny et al. [22] do note however that a limitedamount may form when the pH remains high enough in the con-crete for a sufficient period of time while research on slag cements[58] attributed ettringite formation as substantially contributing tothe damage produced by MgSO4 solutions.

Gollop and Taylor [51,58] concluded in their analysis that theresistance of GGBS concretes to attack by sulfates increases withdecreasing levels of Al2O3. Lower levels of C3A were noted by otherresearchers [16,29] in reducing the harmful effects of exposure tosodium sulfate. In using cement pastes in their analysis however,Gollop and Taylor neglected the effects of the aggregate-pasteinterface previously considered important in analysing a sulfate/sulfuric acid attack [49,59–61]. Their addition of increasing levelsof GGBS up to a level of 92% increased resistance to attack by so-dium sulfate solutions but had the opposite effect when exposedto magnesium sulfate. In an assessment of 150 mm � 75 mm rein-forced concrete cylinder specimens exposed to a 2.1% SO2�

4 sulfatesolution, Al-Amoudi [61] indicated that for a 60% GGBS replace-ment level, deterioration in the mixed magnesium/sodium basedsolution was considered significant. It was concluded that GGBS

mixes fared poorest when compared to other cement replacementmaterials including silica fume (10% replacement) and fly ash (20%replacement). In assessing results from a study by the BRE [25,46],Osborne [29] also came to similar conclusions regarding the effectsof magnesium and sodium sulfate solutions and the use of highpercentages of GGBS as a cement replacement. The TEG one-yearreview [62] also noted the benefit of a 70% GGBS replacement levelwith limestone cement and good quality carbonate aggregateagainst conventional forms of sulfate attack.

4.4. Simulation of the biological corrosion process

In a simulated wet/dry 17-day attack cycle Vincke et al. [21] ex-posed 2 � 2 � 5 cm specimens of concrete to a biological sulfursolution containing Thiobacilli bacteria following an incubationperiod in an H2S environment. After a total of 51 days and three cy-cles, the specimens made with a CEM I Portland cement and CEMIII blast-furnace slag cement were analysed in terms of weight loss.Results indicated that both mixes performed similarly. De Belieet al. [9] used an almost identical process to the above [21], usingspecimens that were 80 mm diameter and 15 mm deep, whichwere subjected to a fourth cycle of 17 days. In their experimentsthey observed the sulfate ion concentration of their solution to in-crease from 2 g/l to 4 g/l which the authors cite as evidence for theproduction of sulfuric acid by the sulfur-oxidising bacteria. The re-sults of their experiments concluded that Portland cement per-formed better than CEM III blast-furnace slag cement. In thisinstance they theorise that owing to the greater surface area ofCEM III the bacteria are able to colonise the surface of the cementmore rapidly than the Portland cement.

Further investigation has revealed other methods of modellingbiological corrosion in the wastewater environment. A simulationchamber was developed by researchers in Hamburg, described byMonteny et al. [4], which allowed the corrosion process to be mod-elled at eight times the in situ level could be reached through theoptimisation of the corrosive environment. Test blocks of60 � 11 � 7 cm were immersed in 10 cm of water at 30 �C andsprayed with Thiobacilli bacteria. H2S gas at 10 ppmv was pumpedinto the chamber and acted as a substrate for the bacteria. Thenumber of bacteria on the surface of the specimens was countedand it was found that the rate of corrosion was dependent on thelevels of T. thiooxidans detected.

Experimental work was also carried out into the corrosionmechanism involved in the deterioration of concrete constructinga simulated sewer pipe 20 m long and a diameter of 15 cm [5]. Testspecimens of mortar bars 4 � 4 � 16 cm were made with the bot-tom half of these bars placed in sewage and exposed to H2S gas notexceeding 300 ppm. Identical mortar bars were placed half sub-mersed into a sewage medium, an autotrophic basal growth cul-ture medium without thiosulfate and distilled water. These wereinoculated every two weeks with T. thiooxidans. Corrosion justabove the waterline was observed on bars in the sewage and auto-trophic basal media. Those in water remained unaffected while thesewage samples displayed the greatest corrosion rate. The authorsconcluded that based on these results the bacteria required a sup-ply of moisture and nutrients to initiate the corrosion processwhile the corrosion products formed were determined to be gyp-sum and secondary ettringite. As with the issue of sulfuric acid at-tack, the possibility of restricting the formation of corrosionproducts through appropriate mix design is not developed.

5. Conclusions

Three research foci were evident in the study of sulfate/sulfuricacid effects on concrete. These are:


� Studies of the biological processes behind the corrosion ofwastewater infrastructure, with particular reference to the roleof sulfate-reducing and sulfur-oxidising bacteria.� Studies of the chemical effects of sulfates and sulfuric acid on

concrete mixes.� Laboratory-based research methodologies, especially those

incorporating the biological effect on concrete.

Chemical tests alone do not fully represent the microbial effectson concrete, although they may help in assessing the types ofdamage that can occur. Some researchers have carried out full-scale laboratory analysis, but it is worth noting that the equipmentnecessary to adequately mimic in situ conditions is invariablycomplicated, cumbersome and custom built [4,63]. The realisationof resources required to undertake such research continues to bean obstacle to addressing this topic. The use of such complexresearch apparatus in routine performance-based specification isimpractical.

Although there exists significant quantities of data on the topicsof sulfate, sulfuric acid and biogenic corrosion of concrete, little hasbeen achieved in the way of formulating an accepted mathematicalmodel of deterioration that incorporates agreed parameters of sig-nificance. This represents a significant knowledge gap and acts as atechnical barrier towards using material design as a means of con-trolling corrosion due to biochemical attack. This continues to inhi-bit the design of durable concrete wastewater infrastructure andhas significant implications for public expenditure in this area.The need to consider the interaction of biological and chemicalprocesses may hold the key to achieving greater progress and allowpractitioners to use concrete mix design as a means of deliveringintended service lives.

Acknowledgements

The authors gratefully acknowledge the financial support pro-vided by Enterprise Ireland Innovation Partnership Project IP/2008/540 and Ecocem Ireland.

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APPENDIX B: Conference Paper

O'Connell, M, McNally, C, Donohue, S, Bonal, J & Richardson, MG. (2009) ‘Assessment of

ultrasonic signals to determine the early age properties of concretes incorporating secondary

cementitious materials’. In: Proceedings 15th European Meeting of Environmental and

Engineering Geophysics, Dublin, 7-9 September.

Near Surface 2009 – 15th

European Meeting of Environmental and Engineering Geophysics

Dublin, Ireland, 7 - 9 September 2009

“Assessment of ultrasonic signals to determine the early age properties of concretes

incorporating secondary cementitious materials”

O’Connell, M., McNally, C., Donohue, S., Bonal, J. and Richardson, M.G.

Summary

Secondary cementitious materials (SCMs) such as ground granulated blast-furnace slag

(GGBS) are used in increasing quantities in concrete practice internationally. While these

materials offer benefits such as reduced CO2 and a more dense microstructure, they also have

drawbacks in terms of slower initial gain of strength. There are significant financial

implications associated with this, as it can lead to delays in the construction process. Key to

overcoming this challenge is the development of a methodology to assess the early-age

stiffness development in concretes manufactured using GGBS. This paper presents the results

of a study into the application of ultrasonic sensors to assess the early age concrete stiffness.

A novel wavelet-based approach is used to overcome the difficulties associated with wave

reflections and classical wave theory is used to determine the concrete small-strain stiffness

based on P and S wave velocities. It was found that the results are largely in agreement with

those obtained using standard strength testing, suggesting potential practical applications of

this method.




Introduction

Secondary cementitious materials (SCMs) such as ground granulated blast-furnace slag

(GGBS) and pulverized fuel ash (PFA) are used in increasing quantities in concrete practice

internationally. These materials are derived from industrial by-products and offer the

significant advantages of abating the high CO2 emissions associated with cement

manufacture, while also making the concrete more dense and durable in the long term

(McNally et al, 2005). However a significant drawback is that SCMs can lead to the concrete

being relatively weak in the initial few days after being cast, leading to costly delays in the

construction process. Decisions on construction sites on when such a concrete is sufficiently

strong to resist applied loading are often based on empirical site practices, which can be quite

punitive to SCMs. In this context, the importance of being able to assess non-destructively the

early-age strength and stiffness of concrete with or without SCMs becomes clear. Ultrasonic

sensors have the potential to allow such an assessment, but to date there is no clear approach

available on the characterisation of concrete at early ages.

Materials

The experimental procedure required three concrete mixes to be prepared with a varying

amount of GGBS to be used as a cement replacement. The cement used was a CEM II A-L

Portland-limestone-cement and GGBS was introduced at replacement levels of 0%, 50% and

70%. Details of the mix design are outlined in Table 1. A series of eight 100mm cubes and

eight 100mm x 200mm concrete cylinders were prepared for each mix with a water/binder

ratio of 0.45. These were left to cure at room temperature for 24 hours prior to demoulding

after which they were stored in a water curing tank at 20˚C for up to 28 days.

Mix ID Cement GGBS 20mm. 10mm. Sand Water

MA 360 0 810 405 685 162

MB 180 180 805 400 680 162

MC 108 252 805 400 162 162

Quantities (kg/m3)

Table 1: Concrete mix designs

Wavelet Analysis of Ultrasonic Signals

It is well known that the Young’s modulus of a material can be determined from the velocity

of the P and S waves across a sample. This approach may be applied using ultrasonic sensors

on concrete samples to allow quantification of the increase in concrete stiffness due to further

hydration of the cementitious materials present. However for this to be done accurately, it is

key that the arrival time of the P and S waves can be determined. For the former this is a

relatively straightforward task as the P-wave arrival can be visually detected from the 1st

discontinuity in the signal. However for the S-wave arrival the situation is less clear, as there

exists a significant amount of interference from the presence of reflected waves off the side

boundaries of the sample. It is in this context that a wavelet-based algorithm was developed to

allow detection of the discontinuity in the signal associated with the S-wave arrival.

A signal may be observed through two main domains: time domain and frequency domain.

The Fourier Transform and its inverse connect these domains and are the main mathematical

tools for signal analysis. The Fourier Transform is perfectly adequate for stationary and

periodic signals and provides a global description of frequency distribution, energy and




overall regularity. However, it involves the complete loss of local time information such as

the location of singularities. A wavelet is a mathematical function used to divide a given

function or continuous-time signal into different frequency components and study each

component with a resolution that matches its scale. A wavelet transform is the representation

of a function by wavelets. The wavelets are scaled and translated copies (known as "daughter

wavelets") of a finite-length or fast-decaying oscillating waveform (known as the "mother

wavelet"). Wavelet transforms have advantages over traditional Fourier transforms for

representing functions that have discontinuities and sharp peaks, and for accurately

deconstructing and reconstructing finite, non-periodic and/or non-stationary signals. The

Wavelet Transform is motivated by the possibility of finding a singularity as it decomposes

the signal into elementary building blocks that are well localized both in time and frequency

(Mallat and Hwang, 1992). The local detail is matched to the scale of the wavelet, so it can

characterise coarse (low frequency) features on large scales and fine (high frequency) features

on small scales.

By assuming the shear wave to be both plane and homogenous, the shear wave arrival in a

bender element test is characterised by the arrival of a broad-band energy. The shear wave is

however preceded by the near-field effect, waves reflecting off the boundaries of the sample

which create a first singular point in the output signal, as illustrated in Fig. 2. It induces an

opposite phase wave preceding the S-wave. The main S-wave arrival creates a second singular

point; however its location in the time domain is usually scrambled by the near-field effect

and the noise. Nevertheless this singularity exists and is defined as a discontinuity in the first

derivative at this time.

Bonal et al. (2008) have presented a novel method of analysing signals using wavelets based

on the Lipschitz exponent (Mallat and Hwang, 1992). The Lipschitz exponent is a well known

tool used to estimate function differentiability. A key feature of the Lipschitz exponent is its

ability to distinguish between singularities due to noise, and those due to events such as the

arrival of the S-wave. In order to accurately determine the first arrival of a shear wave using

wavelets, Bonal et al (2008) followed several maxima lines of the wavelet transform modulus

across a range of scales. The local Lipschitz exponents are determined and the discontinuities

sorted based on this result. They observed the first arrival to be among these singular points

with a local Lipschitz exponent of almost 1; this value is variable but must be compatible with

the characteristics of the input function. This algorithm was then implemented using a Python

script; this approach for wavelet based singularity detection does not give automated results,

but nonetheless directs us to points of interest within the signal.

Methodology

The investigation required S-wave and P-wave ultrasonic readings to be taken on cubes at

one, three, eight, fourteen and twenty-eight days following casting of the specimens. Two sets

of transducers were used for this purpose in conjunction with a square wave pulser-receiver in

‘through-transmission’ mode. The S-wave transducers had a frequency of 0.1 MHz, the P-

wave transducers 50 kHz. For ultrasonic S-wave measurements each transducer was coupled

directly opposite the other using a shear wave couplant gel. A 100V amplitude pulse was

emitted into the specimen for a duration of two minutes and readings were recorded using a

digital oscilloscope connected to a laptop computer. A similar procedure was used for P-

waves with a P-wave couplant gel. The previously described Python script was now

employed to locate the first S-wave arrival; the application of this script is shown in Fig. 2.

To calculate static Young’s modulus for each mix at eight, fourteen and twenty-eight days

tests were carried out in accordance with BS 1881-121 (1983). Extensometers were used to

determine the mean micro-strain of the cylinder at the upper and basic applied stresses.




Fig 1: Ultrasonic measurement experimental set-up: (L-R: laptop, oscilloscope, pulser-

receiver, transducers, 100mm cube and couplant gels)

With the stresses known and the micro-strain readings given by the extensometers, a static

Young’s modulus value to the nearest 100 N/mm2 was calculated for each sample tested.

From ultrasonic testing, the velocity of the P-wave (VP) and the S-wave (VS) can be

calculated. Knowing these, the small strain shear modulus and the Poisson’s ratio can be

determined from Eqn 1 and 2 respectively. Using these values the small strain Young’s

modulus can then be ascertained (Eqn 3).

Eqn 1

Eqn 2

Eqn 3

Fig. 2: S-wave signal showing singularity detection

using a Python script

Results

The results for the experimental testing programme are shown below in Fig. 3. The trends

observed in small strain Young’s modulus, static Young’s modulus and compressive strength

are broadly in line with what is expected for each of the three concrete mixes. The 70%

GGBS mix is clearly defined as being the slowest to develop strength and stiffness at early

ages, although it can be seen that this does gradually improve over time. The shape of the

curves for strength and small-strain stiffness are also quite similar, giving confidence in the

results produced using the wavelet singularity detection algorithm. The approach also appears

more sensitive than the standard static modulus of elasticity, which suggests very little

difference in the concrete properties, regardless of GGBS content.




Fig. 3: Results of experimental testing programmes

Conclusions

Based on the presented results a number of conclusions can be drawn:

• A wavelet-based approach is a valid tool for determining the shear wave velocities in

concrete samples, and is capable of overcoming the issues associated with reflected

waves. However care is needed in determining appropriate Lipschitz exponents.

• The small strain Young’s modulus and compressive strengths for early age concrete

follow similar trends for all GGBS contents; the static modulus of elasticity appears

less sensitive to variations in the GGBS.

• Ultrasonic sensors have the potential to be used in this application, with potentially

significant savings to companies seeking to use secondary cementitious materials in

concrete practice.

Acknowledgements

The authors would like to acknowledge the financial support of Ecocem Ireland Ltd. and the

Enterprise Ireland Innovation Partnership programme (grant no IP/2008/0540). The assistance

of Mr. Eoin Dunne of Trinity College Dublin is also gratefully acknowledged.

References

Bonal, J., Donohue, S. & McNally, C., (2008) Examination of a novel wavelet-based

approach for bender element testing. In: Cannon, E., West, R. & Fanning, P. eds. Bridge and

Infrastructure Research in Ireland, BRI 2008, Galway, Ireland, pp.435–442 .

Mallat, S. and Hwang, W.L., (1992) Singularity detection and processing with wavelets.

Information Theory, IEEE Transactions, Vol. 38 (2) pp.617–643, 1992.

McNally, C., Richardson, M.G., Evans, C., & Callanan, T., (2005) Determination of chloride

diffusion coefficients for use with performance-based specifications. Proceedings of the 6th

International Congress on Global Construction: Ultimate Concrete Opportunities;

Application of Codes, Designs and Regulations Dundee, pp.321–327.

APPENDIX C: Sodium Sulfate Expansion Data

Days ∆L (%) P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0 0.000 0.01 0.01 56 0.006 0.003 0.004 0.01 84 0.012 0.007 0.01 0.016 112 0.025 0.018 0.019 0.027 140 0.027 0.031 0.024 0.029 175 0.029 0.029 0.026 0.031 196 0.035 0.034 0.031 0.037 224 0.043 0.046 0.041 0.046 252 0.045 0.053 0.046 0.047 280 0.051 0.062 0.045 0.05 308 0.06 0.077 0.053 0.058 336 0.066 0.090 0.058 0.062 364 0.073 0.109 0.069 0.072 392 0.081 0.128 0.077 0.078 420 0.101 0.154 0.093 0.092 448 0.105 0.182 0.102 0.097 476 0.119 0.222 0.119 0.114 504 0.141 0.268 0.138 0.131

0

0.05

0.1

0.15

0.2

0.25

0.3

0 56 112 168 224 280 336 392 448 504 560

Ex

pa

nsi

on

%

Days Exposure

CEM II-A/L 100%

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.004 0.006 0.004 0.006 56 0.006 0.007 0.008 0.005 84 0.012 0.012 0.009 0.011 112 0.019 0.018 0.013 0.012 140 0.015 0.018 0.016 0.015 175 0.013 0.016 0.015 0.019 196 0.015 0.017 0.016 0.018 224 0.017 0.017 0.017 0.020 252 0.018 0.020 0.017 0.021 280 0.017 0.022 0.020 0.024 308 0.018 0.022 0.021 0.026 336 0.018 0.024 0.022 0.026 364 0.018 0.024 0.022 0.027 392 0.021 0.026 0.026 0.03 420 0.021 0.028 0.025 0.031 448 0.022 0.030 0.027 0.032 476 0.026 0.030 0.030 0.033 504 0.027 0.032 0.030 0.035

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 56 112 168 224 280 336 392 448 504 560

Ex

pa

nsi

on

%

Days Exposure

CEM II-A/L + 50% GGBS

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.005 0.002 0.008 0.005 56 0.004 0.004 0.002 0.004 84 0.008 0.010 0.012 0.012 112 0.010 0.010 0.014 0.010 140 0.013 0.015 0.016 0.014 175 0.017 0.012 0.015 0.014 196 0.02 0.014 0.017 0.016 224 0.019 0.014 0.017 0.017 252 0.022 0.017 0.020 0.019 280 0.024 0.018 0.022 0.02 308 0.026 0.021 0.023 0.025 336 0.026 0.020 0.023 0.023 364 0.026 0.021 0.024 0.024 392 0.029 0.024 0.027 0.029 420 0.028 0.026 0.027 0.027 448 0.034 0.030 0.029 0.03 476 0.033 0.030 0.031 0.032 504 0.033 0.031 0.035 0.036

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 56 112 168 224 280 336 392 448 504 560

Ex

pa

nsi

on

%

Days Exposure

CEMII-A/L + 70% GGBS

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.013 0.003 0.008 0.014 56 0.025 0.015 0.022 0.026 84 0.029 0.024 0.031 0.034 119 0.037 0.031 0.041 0.046 140 0.048 0.043 0.056 0.058 168 0.059 0.055 0.071 0.072 196 0.072 0.068 0.086 0.089 224 0.088 0.084 0.107 0.109 252 0.109 0.104 0.134 0.132 280 0.123 0.122 0.162 0.155 308 0.153 0.153 0.209 0.196 336 0.185 0.184 0.258 0.236 364 0.249 0.239 0.341 0.315 392 0.309 0.297 0.445 0.404 420 0.407 0.377 0.571 0.52 448 0.546 0.502 0.725 0.664

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 56 112 168 224 280 336 392 448 504

Ex

pa

nsi

on

%

Days Exposure

CEM I 100%

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0.000 0 0 28 0.003 0.008 0 0.002 56 0.006 0.012 0.006 0.008 84 0.015 0.016 0.009 0.013 119 0.013 0.017 0.014 0.021 140 0.018 0.021 0.017 0.024 168 0.016 0.024 0.018 0.026 196 0.019 0.026 0.021 0.028 224 0.02 0.028 0.023 0.031 252 0.021 0.033 0.025 0.034 280 0.023 0.034 0.026 0.036 308 0.023 0.034 0.028 0.038 336 0.024 0.039 0.029 0.039 364 0.028 0.041 0.034 0.042 392 0.03 0.042 0.034 0.044 420 0.031 0.046 0.035 0.046 448 0.033 0.049 0.037 0.047

0

0.01

0.02

0.03

0.04

0.05

0.06

0 56 112 168 224 280 336 392 448 504

Ex

pa

nsi

on

%

Days Exposure

CEM I + 70% GGBS

Prism 1

Prism 2

Prism 3

Prism 4

Days ∆L (%)P1 ∆L (%)P2 ∆L (%)P3 ∆L (%)P4 0 0 0 0 0 28 0 0 0 0.001 56 0 0.003 0.002 0.006 84 0.003 0.007 0.004 0.009 112 0.008 0.012 0.01 0.012 140 0.012 0.016 0.014 0.014 168 0.015 0.02 0.018 0.019 196 0.022 0.024 0.023 0.023 224 0.024 0.029 0.027 0.026 252 0.024 0.031 0.031 0.028 280 0.032 0.036 0.036 0.028 308 0.041 0.044 0.044 0.037 336 0.048 0.053 0.051 0.042 364 0.051 0.059 0.058 0.045 392 0.064 0.068 0.067 0.054 420 0.071 0.075 0.073 0.06

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 56 112 168 224 280 336 392 448

Ex

pa

nsi

on

%

Days Exposure

SRPC 100%

Prism 1

Prism 2

Prism 3

Prism 4

Results Contd: Expansion vs time 0.5

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM II 100%

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM II + 50% GGBS

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 2 4 6 8 10 12 14 16 18 20

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM II + 70% GBS

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM I 100%

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

CEM I + 70% GGBS

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 5 10 15 20 25

Ex

pa

nsi

on

(%

)

Time ^ 0.5(Days)

SRPC 100%

APPENDIX D: Concrete Permeability and Sorption Tests

Air permeability results

y = -0.054x + 6.2021

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MA53

y = -0.0283x + 6.1883

5.7

5.75

5.8

5.85

5.9

5.95

6

6.05

6.1

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MA16

y = -0.0473x + 6.1426

5.4

5.5

5.6

5.7

5.8

5.9

6

0 5 10 15 20

Ln(P

ress

ure

)

Time mins)

MB15

y = -0.013x + 6.200

5.98

6

6.02

6.04

6.06

6.08

6.1

6.12

6.14

6.16

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MB16

y = -0.0555x + 6.2162

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MC15

y = -0.018x + 6.221

5.9

5.95

6

6.05

6.1

6.15

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MC16

y = -0.0738x + 6.1296

4.8

5

5.2

5.4

5.6

5.8

6

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MD15

y = -0.015x + 6.224

5.95

6

6.05

6.1

6.15

6.2

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

MD16

y = -0.0345x + 6.1994

5.65

5.7

5.75

5.8

5.85

5.9

5.95

6

6.05

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

ME15

y = -0.014x + 6.235

6

6.02

6.04

6.06

6.08

6.1

6.12

6.14

6.16

6.18

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

ME16

y = -0.082x + 6.1198

4.8

5

5.2

5.4

5.6

5.8

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

SR15

y = -0.006x + 6.223

6.13

6.14

6.15

6.16

6.17

6.18

6.19

6.2

0 5 10 15 20

Ln(P

ress

ure

)

Time (mins)

SR16

Water permeability results

y = 3.87E-08x + 1.23E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA53

y = 1.78E-08x - 9.05E-09

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

7E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA16

y = 2.35E-08x + 6.28E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB15

y = 1.30E-08x + 1.40E-08

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

7E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB16

y = 3.12E-08x - 2.85E-09

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC15

y = 1.96E-08x + 3.96E-08

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC16

y = 7.57E-08x + 1.96E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

3.00E-07

3.50E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD15

y = 2.68E-08x + 1.26E-08

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD16

y = 4.07E-08x + 1.49E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME15

y = 2.15E-08x - 1.58E-09

0

2E-08

4E-08

6E-08

8E-08

0.0000001

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME16

y = 6.44E-08x + 2.96E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

3.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR15

y = 2.25E-08x + 5.29E-09

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR16

Water sorptivity

y = 1.56E-08x - 6.25E-09

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA53

y = 2.27E-08x + 1.59E-08

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MA16

y = 5.07E-09x + 6.55E-09

0

5E-09

1E-08

1.5E-08

2E-08

2.5E-08

3E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB15

y = 4.04E-09x + 1.76E-08

0

5E-09

1E-08

1.5E-08

2E-08

2.5E-08

3E-08

3.5E-08

4E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MB16

y = 2.59E-08x - 4.23E-09

0.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC15

y = 1.59E-08x - 3.35E-08

0

5E-09

1E-08

1.5E-08

2E-08

2.5E-08

3E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MC16

y = 3.97E-08x + 2.36E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD15

y = 1.45E-08x - 1.21E-08

0

1E-08

2E-08

3E-08

4E-08

5E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

MD16

y = 2.44E-08x - 2.35E-08

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

7E-08

8E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME15

y = 2.66E-08x + 5.75E-09

0.0E+00

2.0E-08

4.0E-08

6.0E-08

8.0E-08

1.0E-07

1.2E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

ME16

y = 5.35E-08x + 2.76E-08

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR15

0

1E-08

2E-08

3E-08

4E-08

5E-08

6E-08

2 2.5 3 3.5 4

Wa

ter

(m3

)

Time ^0.5

SR16

APPENDIX E: Sulfuric Acid Testing: Mass Loss Data (brushed)


CUBE No. 0 1 2 3 4 8 12 16 20 24 5 2447 2449 2448 2449 2453 15 2434 2437 2436 2435 2435 2436 16 2443 2445 2444 2443 2445 2446 2446 2447 2446 2446 6 2436 2438 2438 2439 2439 7 2449 2451 2451 2451 2455 2453 8 2448 2451 2451 2451 2452 2453 2454 2454 2454 2454 9 2453 2461 2468 2446 2442 10 2456 2464 2473 2449 2446 2357 11 2453 2462 2472 2448 2444 2344 2238 2147 2071 1999 12 2487 2511 2517 2498 2497 13 2462 2487 2493 2475 2473 2406 14 2473 2500 2502 2486 2485 2415 2318 2242 2170 2104 Prism No. 1 3549 3550 3548 3550 3544 3550 3551 3551 3550 3552 2 3535 3527 3526 3528 3528 3527 3528 3528 3529 3529 3 3572 3582 3593 3569 3570 3395 3227 3101 2996 2891 4 3596 3611 3623 3588 3582 3422 3256 3128 3018 2919

∆ MASS MIX MA

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 5 0 33 17 33 100 15 0 50 33 17 17 16 0 33 17 0 33 50 50 67 50 50 6 0 33 33 50 50 0 7 0 33 33 33 100 67 8 0 50 50 50 67 83 100 100 100 100 9 0 133 250 -117 -183 10 0 133 283 -117 -167 -1650 11 0 150 317 -83 -150 -1817 -3583 -5100 -6367 -7567 12 0 436 545 200 182 13 0 455 564 236 200 -1018 14 0 491 527 236 218 -1055 -2818 -4200 -5509 -6709 PRISM No. 1 0 12 -12 12 -58 12 23 23 12 35 2 0 -93 -104 -81 -81 -93 -81 -81 -70 -70 3 0 116 243 -35 -23 -2052 -4000 -5461 -6678 -7896 4 0 174 313 -93 -162 -2017 -3942 -5426 -6701 -7849


CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2423 2426 2426 2426 2424 4 2434 2436 2436 2437 2436 5 2421 2422 2422 2423 2422 2422 2423 2423 2423 2424 6 2424 2426 2427 2426 2425 2425 7 2423 2426 2424 2425 2425 2425 8 2436 2437 2438 2436 2437 2437 2438 2438 2438 2438 9 2445 2441 2438 2422 2411 10 2429 2425 2426 2405 2394 2273 11 2442 2440 2434 2417 2406 2281 2175 2099 2016 1956 12 2485 2484 2488 2467 2458 13 2485 2485 2487 2472 2463 2361 14 2456 2452 2455 2435 2427 2325 2238 2161 2082 2019 PRISM No. 1 3485 3486 3487 3484 3485 3485 3486 3487 3486 3487 2 3468 3470 3470 3468 3470 3470 3470 3470 3471 3473 3 3494 3483 3488 3466 3448 3281 3138 3022 2903 2814 4 3498 3496 3504 3480 3463 3303 3156 3044 2931 2845

∆ MASS MIX MB

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 50 50 50 17 4 0 33 33 50 33 5 0 17 17 33 17 17 33 33 33 50 6 0 33 50 33 17 17 7 0 50 17 33 33 33 8 0 17 33 0 17 17 33 33 33 33 9 0 -67 -117 -383 -567 10 0 -67 -50 -400 -583 -2600 11 0 -33 -133 -417 -600 -2683 -4450 -5717 -7100 -8100 12 0 -18 55 -327 -491 13 0 0 36 -236 -400 -2255 14 0 -73 -18 -382 -527 -2382 -3964 -5364 -6800 -7945 PRISM No. 1 0 12 23 -12 0 0 12 23 12 23 2 0 23 23 0 23 23 23 23 35 58 3 0 -128 -70 -325 -533 -2470 -4128 -5472 -6852 -7884 4 0 -23 70 -209 -406 -2261 -3965 -5264 -6574 -7571


CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2437 2438 2439 2438 2437 4 2434 2437 2436 2436 2435 5 2439 2441 2441 2441 2440 2441 2442 2442 2440 2442 6 2421 2424 2425 2423 2423 2424 7 2439 2440 2441 2441 2440 2441 8 2438 2440 2440 2439 2439 2439 2440 2440 2438 2441 9 2407 2404 2410 2394 2387 10 2435 2433 2439 2427 2420 2311 11 2447 2443 2451 2438 2424 2311 2205 2122 2051 1986 12 2478 2478 2485 2471 2461 13 2494 2498 2504 2491 2482 2379 14 2472 2475 2481 2470 2457 2353 2272 2198 2135 2078 PRISM No. 1 3449 3451 3452 3452 3450 3450 3452 3451 3450 3453 2 3472 3477 3476 3475 3476 3475 3476 3475 3475 3478 3 3515 3512 3520 3507 3494 3370 3228 3107 2998 2912 4 3475 3476 3486 3471 3452 3334 3193 3064 2957 2868

∆ MASS MIX MC

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 17 33 17 0 4 0 50 33 33 17 5 0 33 33 33 17 33 50 50 17 50 6 0 50 67 33 33 50 7 0 17 33 33 17 33 8 0 33 33 17 17 17 33 33 0 50 9 0 -50 50 -217 -333 10 0 -33 67 -133 -250 -2067 11 0 -67 67 -150 -383 -2267 -4033 -5417 -6600 -7683 12 0 0 127 -127 -309 13 0 73 182 -55 -218 -2091 14 0 55 164 -36 -273 -2164 -3636 -4982 -6127 -7164 PRISM No. 1 0 23 35 35 12 12 35 23 12 46 2 0 58 46 35 46 35 46 35 35 70 3 0 -35 58 -93 -243 -1681 -3328 -4730 -5994 -6991 4 0 12 128 -46 -267 -1635 -3270 -4765 -6006 -7038


CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2519 2522 2522 2521 2520 4 2516 2518 2518 2518 2517 5 2516 2519 2518 2518 2518 2518 2519 2519 2519 2518 6 2527 2529 2529 2529 2528 2529 7 2515 2517 2517 2516 2517 2517 8 2500 2504 2502 2503 2502 2503 2504 2503 2503 2502 9 2450 2435 2436 2419 2409 10 2446 2433 2434 2419 2411 2298 11 2446 2432 2432 2414 2404 2297 2191 2104 2020 1957 12 2502 2496 2497 2482 2475 13 2496 2496 2496 2481 2474 2377 14 2481 2480 2481 2468 2457 2364 2270 2199 2124 2063 PRISM No. 1 3527 3528 3530 3530 3528 3529 3531 3530 3532 3531 2 3499 3504 3505 3503 3502 3503 3503 3504 3504 3504 3 3512 3497 3497 3477 3464 3325 3174 3061 2950 2867 4 3503 3484 3489 3461 3444 3297 3136 3024 2916 2838

∆ MASS MIX MD

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 50 50 33 17 4 0 33 33 33 17 5 0 50 33 33 33 33 50 50 50 33 6 0 33 33 33 17 33 7 0 33 33 17 33 33 8 0 67 33 50 33 50 67 50 50 33 9 0 -250 -233 -517 -683 10 0 -217 -200 -450 -583 -2467 11 0 -233 -233 -533 -700 -2483 -4250 -5700 -7100 -8150 12 0 -109 -91 -364 -491 13 0 0 0 -273 -400 -2164 14 0 -18 0 -236 -436 -2127 -3836 -5127 -6491 -7600 Prism No. 1 0 12 35 35 12 23 46 35 58 46 2 0 58 70 46 35 46 46 58 58 58 3 0 -174 -174 -406 -557 -2168 -3919 -5229 -6516 -7478 4 0 -220 -162 -487 -684 -2388 -4255 -5554 -6806 -7710


CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2447 2450 2448 2448 2448 4 2437 2437 2440 2438 2438 5 2423 2424 2424 2425 2425 2425 2426 2425 2425 2426 6 2427 2427 2427 2428 2427 2428 7 2411 2412 2413 2413 2413 2413 8 2446 2449 2448 2448 2448 2448 2449 2448 2449 2449 9 2432 2432 2437 2416 2408 10 2420 2422 2425 2407 2396 2303 11 2433 2435 2440 2418 2409 2313 2210 2127 2042 1982 12 2471 2483 2486 2460 2458 13 2486 2493 2498 2481 2472 2386 14 2470 2480 2484 2464 2455 2372 2284 2215 2144 2080 PRISM No. 1 3532 3536 3537 3536 3536 3536 3536 3535 3535 3535 2 3471 3476 3476 3475 3473 3474 3475 3475 3476 3476 3 3494 3468 3492 3473 3460 3331 3198 3084 2974 2896 4 3469 3489 3478 3451 3440 3329 3199 3076 2952 2870

∆ MASS MIX ME

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 50 17 17 17 4 0 0 50 17 17 5 0 17 17 33 33 33 50 33 33 50 6 0 0 0 17 0 17 7 0 17 33 33 33 33 8 0 50 33 33 33 33 50 33 50 50 9 0 0 83 -267 -400 10 0 33 83 -217 -400 -1950 11 0 33 117 -250 -400 -2000 -3717 -5100 -6517 -7517 12 0 218 273 -200 -236 13 0 127 218 -91 -255 -1818 14 0 182 255 -109 -273 -1782 -3382 -4636 -5927 -7091 PRISM No. 1 0 46 58 46 46 46 46 35 35 35 2 0 58 58 46 23 35 46 46 58 58 3 0 -301 -23 -243 -394 -1890 -3432 -4754 -6029 -6933 4 0 232 104 -209 -336 -1623 -3130 -4557 -5994 -6945


CUBE No. 0 1 2 3 4 8 12 16 20 24 3 2481 2482 2482 2482 2482 4 2459 2461 2462 2460 2460 2461 5 2470 2471 2472 2471 2471 2472 2472 2472 2472 2471 6 2478 2480 2479 2480 2480 7 2482 2483 2483 2483 2483 2484 8 2458 2461 2460 2460 2460 2461 2462 2461 2462 2460 9 2461 2451 2448 2431 2423 10 2478 2472 2469 2447 2437 2337 11 2464 2452 2450 2434 2425 2326 2190 2105 2028 1962 12 2520 2526 2524 2508 2500 13 2509 2514 2512 2498 2490 2415 14 2522 2530 2529 2512 2507 2421 2309 2232 2159 2092 PRISM No. 1 3543 3546 3546 3546 3545 3545 3546 3546 3547 3548 2 3550 3551 3549 3550 3550 3550 3552 3553 3553 3553 3 3542 3541 3537 3512 3504 3395 3211 3075 2965 2875 4 3555 3556 3552 3524 3514 3395 3205 3077 2968 2881

∆ MASS MIX SR

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 3 0 17 17 17 17 4 0 33 50 17 17 33 5 0 17 33 17 17 33 33 33 33 17 6 0 33 17 33 33 7 0 17 17 17 17 33 8 0 50 33 33 33 50 67 50 67 33 9 0 -167 -217 -500 -633 10 0 -100 -150 -517 -683 -2350 11 0 -200 -233 -500 -650 -2300 -4567 -5983 -7267 -8367 12 0 109 73 -218 -364 13 0 91 55 -200 -345 -1709 14 0 145 127 -182 -273 -1836 -3873 -5273 -6600 -7818 PRISM No. 1 0 35 35 35 23 23 35 35 46 58 2 0 12 -12 0 0 0 23 35 35 35 3 0 -12 -58 -348 -441 -1704 -3838 -5414 -6690 -7733 4 0 12 -35 -359 -475 -1855 -4058 -5542 -6806 -7814


MA MB MC MD ME SR

0 0 0 0 0 0 0

1 261 51 6 153 66 15

2 380 25 105 137 139 55

3 29 335 107 408 198 353

4 11 513 285 567 337 483

8 1601 2442 1984 2300 1844 1959

12 3586 4127 3567 4065 3415 4084

16 5047 5454 4974 5402 4762 5553

20 6314 6832 6182 6728 6117 6841

24 7505 7875 7219 7735 7121 7933

APPENDIX F: Sulfuric Acid Testing: Mass Loss Data (unbrushed)


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2468 2473 2480 2482 2478 2406 2304 2258 2219 2188 18 2472 2477 2486 2488 2487 2426 2318 2275 2226 2201

∆ MASS MIX MA

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 91 218 255 182 -1127 -2982 -3818 -4527 -5091 18 0 91 255 291 273 -836 -2800 -3582 -4473 -4927


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2469 2484 2498 2516 2512 2390 2294 2258 2220 2213 18 2494 2511 2526 2542 2548 2409 2310 2272 2239 2230

∆ MASS MIX MB

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 273 527 855 782 -1436 -3182 -3836 -4527 -4655 18 0 309 582 873 982 -1545 -3345 -4036 -4636 -4800


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2459 2482 2496 2516 2529 2394 2299 2255 2224 2231 18 2484 2477 2517 2534 2549 2426 2329 2291 2262 2257

∆ MASS MIX MC

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 418 673 1036 1273 -1182 -2909 -3709 -4273 -4145 18 0 -127 600 909 1182 -1055 -2818 -3509 -4036 -4127


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2553 2563 2575 2580 2581 2471 2378 2331 2287 2266 18 2544 2557 2569 2580 2578 2453 2366 2325 2286 2267

∆ MASS MIX MD

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 182 400 491 509 -1491 -3182 -4036 -4836 -5218 18 0 236 455 655 618 -1655 -3236 -3982 -4691 -5036


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2478 2498 2512 2525 2534 2424 2326 2281 2258 2262 18 2483 2503 2513 2531 2541 2424 2338 2288 2260 2260

∆ MASS MIX ME

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24 17 0 364 618 855 1018 -982 -2764 -3582 -4000 -3927 18 0 364 545 873 1055 -1073 -2636 -3545 -4055 -4055


CUBE No. 0 1 2 3 4 8 12 16 20 24 17 2510 2526 2540 2549 2540 2435 2337 2291 2245 2220 18 2529 2549 2556 2557 2552 2459 2351 2303 2257 2229

∆ MASS MIX SR

(g/m2) WEEK CUBE No. 0 1 2 3 4 8 12 16 20 24

0 291 545 709 545 -1364 -3145 -3982 -4818 -5273 0 364 491 509 418 -1273 -3236 -4109 -4945 -5455


MA MB MC MD ME SR

0 0 0 0 0 0 0

1 61 194 97 140 243 219

2 158 370 425 286 389 346

3 183 577 649 377 577 407

4 153 589 820 383 692 323

8 982 1491 1118 1573 1027 1318

12 2891 3264 2864 3209 2700 3191

16 3700 3936 3609 4009 3564 4045

20 4500 4582 4155 4764 4027 4882

24 5009 4727 4136 5127 3991 5364

APPENDIX G: Sulfuric Acid Testing: Cube Strength Data

Compressive Strength: Mix MA


0 57 57 0% 28 57 50 12% 56 58 35 40% 168 60 21 65%

Compressive Strength: Mix MB


0 61 61 0% 28 65 53 18% 56 65 35 46% 168 70 19 74%

Compressive Strength: Mix MC


0 58 58 0% 28 58 51 12% 56 63 37 42% 168 65 22 66%

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168C

ub

e s

tre

ng

th (

MP

a)

Days


Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days


Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days


Cubes in water

Cubes in acid

Compressive Strength: Mix MD


0 65 65 0% 28 71 56 21% 56 75 43 42% 168 77 19 76%

Compressive Strength: Mix ME


0 54 54 0% 28 57 49 14% 56 59 34 42% 168 69 18 74%

Compressive Strength: Mix SR


0 60 60 0% 28 58 59 0% 56 68 41 40% 168 75 21 72%

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

)

Days

MD - 100% CEM I

Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

str

en

gth

(M

Pa

Days


Cubes in water

Cubes in acid

0

10

20

30

40

50

60

70

80

0 28 56 84 112 140 168

Cu

be

Str

en

gth

(M

pa

)

Days

SR - 100% SRPC

Cubes in water

Cubes in acid

APPENDIX H: Sulfuric Acid Testing: Expansion Data

MB1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.62 3.332 Wk 0 6.634 3.517 6.717 3.42 6.732 3.601 Wk 4 5.79 2.501 0.003 Wk 4 5.814 2.661 -0.009 5.852 2.557 0.001 5.869 2.712 -0.010 Wk 8 6.454 3.158 0.000 Wk 8 6.46 3.299 -0.012 6.46 3.158 -0.002 6.46 3.304 -0.010 Wk 12 6.147 2.83 -0.008 Wk 12 6.146 3.001 -0.006 6.151 2.862 0.003 6.153 2.976 -0.018 Wk 16 6.052 2.748 -0.003 Wk 16 6.055 2.888 -0.014 6.059 2.752 -0.004 6.059 2.885 -0.017 Wk 20 6.242 2.948 0.001 Wk 20 6.246 3.082 -0.013 6.249 2.949 -0.001 6.251 3.083 -0.015 Wk 24 6.599 3.298 -0.002 Wk 24 6.606 3.435 -0.016 6.608 3.301 -0.004 6.61 3.434 -0.018 MB3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 Wk 0 6.689 3.48 6.779 3.558 Wk 4 Wk 4 5.85 2.687 0.023 5.88 2.668 0.004 Wk 8 Wk 8 6.46 3.226 -0.005 NO READINGS 6.461 -0.008 Wk 12 Wk 12 6.151 2.862 -0.027 6.081 2.823 -0.015 Wk 16 Wk 16 6.058 2.807 -0.012 6.06 2.798 -0.016 Wk 20 Wk 20 6.249 2.989 -0.016 6.252 2.992 -0.016 Wk 24 Wk 24 6.608 3.344 -0.017

6.608 3.347 -0.016 MB1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.981 2.621 Wk 0 5.956 2.75 5.989 2.625 5.994 2.761 Wk 4 6.618 3.345 0.036 Wk 4 6.664 3.422 -0.004 6.851 3.476 -0.004 6.869 3.631 -0.002 Wk 8 6.189 2.807 -0.007 Wk 8 6.19 2.942 -0.006 6.192 2.823 -0.002 6.192 2.937 -0.009 Wk 12 6.436 3.138 0.026 Wk 12 6.234 3.014 0.005 6.424 3.047 -0.005 6.448 3.209 -0.002 Wk 16 6.229 2.887 0.009 Wk 16 6.232 2.99 -0.004 6.249 2.861 -0.010 6.251 3.005 -0.005 Wk 20 6.596 3.213 -0.008 Wk 20 6.605 3.352 -0.008 6.621 3.23 -0.011 6.62 3.357 -0.012 Wk 24 6.433 3.046 -0.009 Wk 24 6.437 3.176 -0.011 6.439 3.047 -0.011 6.439 3.178 -0.011 MB3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MB4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.975 2.884 Wk 0 5.985 2.851 5.997 2.874 6 2.822 Wk 4 6.802 3.685 0.002 Wk 4 6.848 3.625 -0.018 6.882 3.725 -0.014 6.883 3.665 -0.016 Wk 8 6.191 3.031 -0.015 Wk 8 6.192 2.981 -0.013 6.192 3.039 -0.012 6.192 2.976 -0.015 Wk 12 6.258 3.22 0.034 Wk 12 6.396 3.188 -0.012 6.47 3.328 -0.008 6.484 3.246 -0.024 Wk 16 6.243 3.056 -0.026 Wk 16 6.245 3.013 -0.022 6.252 3.082 -0.019 6.254 3.019 -0.023 Wk 20 6.61 3.427 -0.024 Wk 20 6.624 3.354 -0.037 6.621 3.424 -0.030 6.618 3.372 -0.027 Wk 24 6.438 3.311 -0.002 Wk 24 6.438 3.177 -0.033 6.438 3.222 -0.037 6.431 3.171 -0.033

MC1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MC2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.135 3.182 Wk 0 6.134 3.085 6.132 3.172 6.133 3.076

Wk 4 6.034 3.07 -0.002 Wk 4 6.035 2.885 -0.037 6.038 3.064 -0.006 6.039 2.893 -0.036

Wk 8 6.214 3.224 -0.012 Wk 8 6.212 3.157 0.001 6.244 3.277 -0.003 6.247 3.142 -0.019

Wk 12 6.05 3.075 -0.006 Wk 12 6.057 2.895 -0.042 6.058 3.075 -0.009 6.059 2.833 -0.068

Wk 16 6.25 3.276 -0.006 Wk 16 6.25 3.027 -0.066 6.248 3.273 -0.006 6.252 3.045 -0.060

Wk 20 6.612 3.635 -0.007 Wk 20 6.612 3.386 -0.068 6.62 3.635 -0.010 6.619 3.381 -0.072

Wk 24 6.434 3.451 -0.009 Wk 24 6.435 3.203 -0.070 6.434 3.451 -0.009 6.436 3.202 -0.071

MC3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MC4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.133 2.949 Wk 0 6.132 3.017 6.133 2.951 6.132 2.881

Wk 4 6.035 2.833 -0.007 Wk 4 6.033 2.721 -0.024 6.039 2.83 -0.010 6.039 2.724 -0.026

Wk 8 6.233 3.07 0.008 Wk 8 6.241 2.959 -0.012 6.247 3.037 -0.010 6.247 2.93 -0.026

Wk 12 6.058 2.829 -0.018 Wk 12 6.054 2.74 -0.025 6.056 2.831 -0.016 6.059 2.73 -0.031

Wk 16 6.251 3.015 -0.021 Wk 16 6.244 2.917 -0.030 6.253 3.016 -0.021 6.251 2.918 -0.033

Wk 20 6.614 3.385 -0.018 Wk 20 6.616 3.386 0.008 6.619 3.379 -0.022 6.62 3.29 -0.032

Wk 24 6.437 3.196 -0.023 Wk 24 6.433 3.088 -0.038 6.438 3.194 -0.024 6.437 3.091 -0.038

MD1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MD2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.147 3.134 Wk 0 6.152 2.98 6.15 3.1 6.15 2.966

Wk 4 6.463 3.374 -0.016 Wk 4 6.466 3.298 0.006 6.468 3.396 -0.009 6.466 3.274 -0.003

Wk 8 6.242 3.141 -0.020 Wk 8 6.246 3.219 0.063 6.249 3.145 -0.022 6.25 3.108 0.017

Wk 12 6.054 2.951 -0.021 Wk 12 6.055 2.98 0.044 6.056 2.953 -0.021 6.057 2.884 0.004

Wk 16 6.249 3.145 -0.022 Wk 16 6.25 3.114 0.019 6.253 3.148 -0.022 6.255 3.07 0.000

Wk 20 6.61 3.502 -0.023 Wk 20 6.611 3.432 0.002 6.612 3.495 -0.027 6.612 3.427 0.000

Wk 24 6.444 3.32 -0.030 Wk 24 6.443 2.253 -0.402 6.446 3.323 -0.029 6.446 3.254 -0.003

MD3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

MD4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 6.149 3.042 Wk 0 6.151 3.132 6.15 3.013 6.15 3.162

Wk 4 6.466 3.235 -0.038 Wk 4 6.464 3.402 -0.017 6.464 3.226 -0.040 6.464 3.399 -0.018

Wk 8 6.248 2.995 -0.046 Wk 8 6.246 3.172 -0.022 6.25 3.01 -0.041 6.25 3.163 -0.027

Wk 12 6.056 2.8 -0.048 Wk 12 6.054 2.984 -0.020 6.059 2.803 -0.048 6.056 2.969 -0.027

Wk 16 6.252 2.986 -0.052 Wk 16 6.253 3.169 -0.026 6.255 2.982 -0.054 6.257 3.162 -0.030

Wk 20 6.611 3.338 -0.054 Wk 20 6.611 3.514 -0.031 6.612 3.331 -0.058 6.611 3.517 -0.030

Wk 24 6.443 3.151 -0.062 Wk 24 6.444 3.334 -0.036 6.446 3.153 -0.062 6.447 3.334 -0.038

ME1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

ME2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.962 2.717 Wk 0 5.964 2.876 5.819 2.559 5.825 2.732

Wk 4 6.464 3.215 0.004 Wk 4 6.466 3.372 0.000 6.444 3.187 0.001 6.434 3.337 -0.002

Wk 8 6.148 2.891 0.001 Wk 8 6.152 3.047 -0.005 6.153 2.883 -0.004 6.153 3.043 -0.007

Wk 12 6.049 2.794 0.002 Wk 12 6.051 2.995 0.015 6.053 2.794 0.000 6.055 2.959 -0.001

Wk 16 6.253 2.989 -0.002 Wk 16 6.253 3.148 -0.005 6.254 2.985 -0.004 6.254 3.147 -0.006

Wk 20 6.614 3.348 -0.002 Wk 20 6.615 3.508 -0.006 6.616 3.347 -0.004 6.616 3.506 -0.007

Wk 24 6.44 3.174 -0.002 Wk 24 6.441 3.332 -0.006 6.443 3.174 -0.004 6.442 3.33 -0.008

ME3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

ME4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.964 2.662 Wk 0 5.797 2.582 5.716 2.574 5.732 2.51

Wk 4 6.467 3.209 0.018 Wk 4 6.466 3.254 0.004 6.46 3.259 0.040 6.466 3.257 0.005

Wk 8 6.153 2.988 0.055 Wk 8 6.151 2.893 -0.014 6.153 2.981 0.052 6.153 2.907 -0.010

Wk 12 6.052 2.882 0.053 Wk 12 6.054 2.787 -0.018 6.054 2.87 0.047 6.055 2.789 -0.018

Wk 16 6.253 3.075 0.050 Wk 16 6.25 2.982 -0.018 6.254 3.062 0.044 6.257 2.981 -0.022

Wk 20 6.615 3.405 0.037 Wk 20 6.615 3.34 -0.021 6.616 3.402 0.035 6.616 3.339 -0.022

Wk 24 6.443 3.222 0.032 Wk 24 6.442 3.158 -0.025 6.443 3.213 0.029 6.443 3.156 -0.026

SR1 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

SR2 WATER Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.683 2.672 Wk 0 5.927 2.592 5.955 2.889 5.955 2.631

Wk 4 6.458 3.224 -0.067 Wk 4 6.461 3.131 0.002 6.464 3.185 -0.085 6.46 3.083 -0.017

Wk 8 6.146 2.869 -0.084 Wk 8 6.15 2.817 0.001 6.15 2.853 -0.092 6.152 2.758 -0.024

Wk 12 6.054 2.748 -0.096 Wk 12 6.055 2.711 -0.004 6.054 2.743 -0.098 6.058 2.678 -0.018

Wk 16 6.255 2.942 -0.099 Wk 16 6.255 2.875 -0.018 6.229 2.905 -0.103 6.236 2.841 -0.024

Wk 20 6.609 3.297 -0.098 Wk 20 6.61 3.222 -0.021 6.61 3.297 -0.099 6.608 3.213 -0.024

Wk 24 6.442 3.123 -0.101 Wk 24 6.444 3.045 -0.026 6.445 3.119 -0.104 6.445 3.044 -0.026

SR3 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

SR4 ACID Ref Bar

(mm)

Reading

(mm)

∆L

(%)

Wk 0 5.937 2.681 Wk 0 5.95 2.715 5.956 2.689 5.957 2.72

Wk 4 6.463 3.129 -0.027 Wk 4 6.462 3.162 -0.025 6.465 3.119 -0.032 6.461 3.156 -0.027

Wk 8 6.15 2.806 -0.031 Wk 8 6.151 2.827 -0.035 6.149 2.804 -0.031 6.154 2.825 -0.037

Wk 12 6.058 2.696 -0.038 Wk 12 6.059 2.734 -0.035 6.056 2.69 -0.040 6.058 2.718 -0.041

Wk 16 6.255 2.893 -0.038 Wk 16 6.255 2.88 -0.055 6.239 2.87 -0.041 6.245 2.923 -0.034

Wk 20 6.611 3.226 -0.047 Wk 20 6.61 3.246 -0.051 6.597 3.201 -0.052 6.6 3.228 -0.054

Wk 24 6.444 3.053 -0.050 Wk 24 6.444 3.067 -0.056 6.445 3.047 -0.052 6.446 3.061 -0.059

Date post:	13-Apr-2015
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Ecocem Use of GGBS Concrete Mixes

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