5-Constituents Materials for Concrete â€“ Aggregates

Constituents Materials for Concrete – Aggregates

AGGREGATES

Based on Materials Passing or Retained on 5mm Sieve

( Fine – SAND, Coarse – STONE)

CONCRETE

Volume of Aggregates > Volume of Cement Paste

Physical Properties of Concrete Dependent on

Corresponding Properties of Aggregates

Specific Heat

Specific Density

Coefficient of Thermal Expansion

Volume Stability – Elastic Modulus, Creep, Shrinkage Page 1 of 55


CONCRETE AGGREGATES

Grouped according to size into fine and coarse aggregates

Separation based on materials passing or retained on nominal

5 mm sieve (max. agg. Size : 5 mm, 10 mm, 20 mm and 40 mm)

Fine Aggregate also known as Sand and Coarse Aggregate as Stone

Natural source (rock) or manufactured from other materials or recycled aggregate (RA) or recycled concrete aggregate (RCA)

Classified by density: lightweight, normal weight, heavy weight

Classified by rock type for coarse aggregates

Fine aggregate classified as Natural Sand or Crushed Stone Sand

(Urgent need to use marginal aggregates for sustainable development)

Page 2 of 55


INHERENT Properties

Important in aiding the selection of an aggregate source

Examples:

Strength, Elastic Modulus, Specific Gravity, Absorption,

Particle Shapes and Textures, Chemical Stability, Wear Resistance

Once confirmed before production, only checked periodically (yearly)

Properties Affecting Mix Design and Quality Control

Properties varying from time to time and affecting concrete properties

Regular assessment to detect fluctuations, and hence to facilitate mix adjustment and control of concrete production.

Examples :

Size, Grading, (consistency, trend of change), moisture content,

amount of deleterious substances (organic matter in sand)

Page 3 of 55


CHEMICAL PROPERTIES OF AGGREGATES

Mineral composition, sulfate, chloride, deleterious materials (mica, shells, organic matters)

Alkali - aggregate reactivity - alkali silica, alkali carbonate

MECHANICAL PROPERTIES OF AGGREGATES

Strength (aggregate crushing value, 10% fine value), modulus of elasticity, hardness (aggregate impact value), abrasion resistance (aggregate abrasion value), wear resistance (% wear by Los Angeles Testing Machine)

Acceptance Testing Prior To Approval For Concrete Production

To Ensure Durability Of Concrete

Page 4 of 55


AGGREGATES

Physical Properties of Major Interest to Civil Engineers

Specific Gravity (or Density) – Strength/Mass ratio

Porosity – Absorption

Particle Size Distribution (or Grading) – Packing, Void

Shape – Descriptive term: rounded, angular, cubical

Semi-empirical Measurement: flaky or elongated

Surface – Descriptive term: smooth, rough

Pores: Internal space besides solid material

Voids: Space between particles of aggregates Page 5 of 55


PHYSTICAL PROPERTIES OF AGGREGATES

Shape (round, irregular, flaky, elongated), Size (maximum, 5 to 75 mm),

Grading (single-sized, graded), Specific Gravity, Absorption,

Moisture Content (oven-dry, saturated-surface-dry, free water),

Density (normal, lightweight, heavyweight)

Specific properties - specific heat, thermal expansion coefficient

Regular and systematic monitoring (moisture content, size and grading)

during concrete production to ensure consistent quality of both fresh

and hardened concrete properties

Page 6 of 55


MOISTURE STATE

• Each piece of aggregate may have some internal pores

• Internal pores only filled with water but external surface

dry - saturated-surface-dry (SSD)

• Water in internal pores = absorption (by mass of oven-dry

aggregate)

• External surface water and water between aggregates

(sand)

- free water (free moisture content)

• Total moisture = free water + absorbed water

(i.e. removed by oven-dry at 105OC or by microwave drying) Page 7 of 55


MOISTURE IN AGGREGATE

Bone-dry Air-dry Saturated and

Surface-dry

Moist (Surface Water)

Absorbed Moisture

(Absorption)

Free Moisture

(Moisture Content)

Effective

Absorption

Effective Absorption May Not Be Fully Achieved During Mixing Page 8 of 55


Role of Aggregate in Concrete

• Aggregates are cheaper than cement

• More economical to include, as much aggregates as technically viable and to minimize the cement content per unit volume of concrete

• Volume fraction of aggregates occupies more than double that of cement paste matrix

• Combined volume of fine and coarse aggregates generally between 60% to 80% of total volume of a concrete mix

• Not only as inert materials serving as economical fillers, aggregates contribute beneficially to properties of concrete such as improving volume stability, abrasion resistance and durability

• Physical properties of concrete are directly related to the corresponding properties of aggregates, such as density, specific heat, and modulus of elasticity

Page 9 of 55


EFFECTS OF GRADING ON MIX DESIGN

• Fineness Modulus (FM) – more than one grading may have similar FM, but not the size distribution

• Change in FM of 0.2 in sand may lead to significant change in water demand for the same workability

• In terms of fineness modulus, maximum daily or total deviation, if taken to extremes, will exceed two to three times the commonly accepted change of 0.2 in the fineness modulus beyond which a change in mix proportions is deemed desirable.

EFFECTS OF SIZE ON MIX DESIGN

• Larger maximum size aggregate has smaller total surface area per unit mass of aggregate

• Lower cement content (kg/m3) needed to coat aggregate surface and more towards providing inter-particle paste for workability

• Lower water content (kg/m3) needed for a given water-cement ratio requirement for strength (140 to 160 kg/m3 in ready-mixed concrete production equipment currently available)

• Lower cement content means less heat of hydration in thick sections of concrete, less shrinkage and creep Page 10 of 55


AGGREGATE TESTING

• It should be noted that most properties of aggregate are difficult to define and measure in absolute terms, e.g. shape & texture

• Acceptance criteria are prescriptive in nature, hence most quantitative values cannot be directly related to performance

• Empirical and arbitrarily chosen methods and equipment are described in details and highly standardized to ensure repeatability and reproducibility of test results.

• Reference should be made to relevant standard specifications whenever necessary.

Desirable to move from testing for Conformity to Performance-

based approach for directly useful quantitative values where possible

Page 11 of 55


AGGREGATES

BS EN 12620: 2002+A1: 2008 Aggregates for concrete

(SS EN 12620: 2008)

Aggregates and filler aggregates obtained by processing natural, manufactured or recycled materials and mixtures of these aggregates for use in concrete

Oven dried particle density greater than 2 000 kg/m3

Examples of some requirements taken to illustrate new approach to specify properties and guidance

Note: ISO 565:1990 Test sieves – Metal wire cloth, perforated metal plate and electroformed sheet

Nominal sizes of openings

Minor difference from BS sieves openings

(to change over soonest convenient – UK adopts basic set plus set 2)

Page 12 of 55

BS EN 12620: 2002+A1: 2008 Aggregates for concrete (SS EN 12620: 2008)

Terms and definitions

Aggregate size

Designation of aggregate in terms of lower (d) and upper (D) sieve

sizes expressed as d/D

Fine aggregate

Designation given to the smaller aggregate sizes with D less than or

equal to 4 mm

Coarse aggregate

Designation given to the larger aggregate sizes with D greater than or

equal to 4 mm and d greater than or equal to 2 mm

Fines

Particle size fraction of an aggregate which passes the 0.063 mm sieve

Filler aggregate

Aggregate, most of which passes a 0.063 mm sieve, which can be

added to construction materials to provide certain properties

Page 13 of 55

BS EN 12620: 2002+A1: 2008 Aggregates for concrete (SS EN 12620: 2008)

Terms and definitions (continued)

Grading

Particle size distribution expressed as the percentages by mass

passing a specific set of sieves

Category

Level of property of an aggregate expressed as a range of values or a

limiting value

Natural aggregate

Aggregate from mineral sources which has been subjected to nothing

more than mechanical processing

Manufactured aggregate

Aggregate of mineral origin resulting from an industrial process

involving thermal or other modification

Recycled aggregate

Aggregate resulting from the processing of inorganic materials

previously used in construction Page 14 of 55

Source: PD 6682-1-2003, Aggregates – Part 1: Aggregates for concrete – Guidance on the use of BS EN 12620, BSI Page 15 of 55


New way to state aggregate size

Aggregate sizes specified using the designation d/D

d = lower sieve size and D = upper sieve size (mm)

Aggregate sizes shall have D/d not less than 1,4

Example : graded coarse aggregate 4/20 (d = 4 and D = 20)

Table 2 – General grading requirements

For D/d > 2 and D > 11,2 mm

G3

Percentage passing by mass Category

G 2 D (40) 1,4 Da (31,5) D (20) d (4) d/2 (2)

100 98 to 100 90 to 99 0 to 15 0 to 5 Gc90/15

a Where the sieves calculated are not exact sieve numbers in the ISO 565:1990 R20 series then the next

nearest sieve size shall be adopted.

For graded coarse aggregates where D > 11,2 mm and D/d > 2

i) all gradings shall comply with the overall limits given in Table 3;

ii) the producer shall document and, on request, declare the typical grading passing the mid-size sieve

and tolerances selected from the categories in Table 3.

Table 3 – Overall limits and tolerances for coarse aggregate grading at mid-size sieve

D/d Mid-size sieve

(mm)

Overall limits and tolerances at mid-size sieves

(percentage passing by mass)

Category

GT

Overall limits Tolerances on producer’s declared typical grading

≥ 4 D/2 (10) 25 to 70 17,5 GT 17,5

Gc90/15

D/d

Page 16 of 55

Source: PD 6682-1-2003, BSI

Page 17 of 55


Single size coarse aggregate :

Example 10/20

For D > 11,2 and D/d 2

Table 2 – General grading requirements only

Example 4/10

For D > 11,2 and D/d 2

Table 2 – General grading requirements only

Percentage passing by mass

2 D (40) 1,4 Da (31,5) D (20) d (10) d/2 (4) Category

100 98 to 100 85 to 99 0 to 20 0 to 5 Gc85/20


2 D (20) 1,4 Da (14) D (10) d (4) d/2 (2) Category

100 98 to 100 85 to 99 0 to 20 0 to 5 Gc85/20

Note: Single size aggregate has less potential for segregation within a stockpile

than a graded aggregate leading to less variability in consistence

Preferred for high performance concrete, e.g. SCC, ≥ C60/75 strength

class

Page 18 of 55


Coarse Aggregate Grading Limits

Page 19 of 55


General Specification

Aggregates for

Concrete

Covers All Uses

Select types of

aggregate for project

Specify properties

needed for project

and their limiting

maximum value in

terms of Category

Page 20 of 55


G4

Shape of coarse aggregates – in terms of flakiness index (EN 933-3)

(Differs from BS 812-105 openings and lower limits are specified)

When required, the flakiness index shall be declared in accordance with the

relevant category specified in Table 8 according to the particular

application or end use

Table 8 – Categories for maximum values of flakiness index

(BS 882 values from PD 6682-1:2002, Table 3)

Flakiness index Category BS 882 maximum value Type of aggregate/use

15

20

35

50

50

FI15

FI20

FI35

FI50

FIDeclared

-

-

40

50

-

Special circumstance, e.g.

pavement surface courses

Crushed rock or gravel

Uncrushed gravel

-

No requirement FINR - -

EN 933-3 bar sieves are different from the slot openings in BS 812-106. This leads

to a lower flakiness index values, therefore the limits specified for flakiness in BS

EN 12620 and BS EN 13043 (bituminous mixtures) are lower than those specified

in BS 882 (concrete) and BS 63 (bituminous mixtures).

BS EN 933-3 catagorizes a particle as flaky if it minimum dimension is less than

half its upper sieve size (D) as defined by the particle size fraction in which it falls. Page 21 of 55

FLAKINESS INDEX – EN 933-3 vs BS 812 (SS 73)

Page 22 of 55


Shape of coarse aggregates – in terms of shape index (EN 933-4)

(Shape index: mass of particles with a ratio of dimension L/E more than 3

expressed as a percentage of total dry mass of particles tested)

L = particle length, maximum dimension of a particle

E = particle thickness, minimum dimension of a particle

When required, the shape index shall be declared in accordance with the

relevant category specified in Table 9 according to the particular

application or end use

Table 9 – Categories for maximum values of shape index

Shape index Category - SI

15

20

40

55

> 55

SI15

SI20

SI40

SI55

SIDeclared

No requirement SINR

Shape index value determined by BS EN 933-4 is different from elongation index

determined by BS 812-105.2. It has been suggested that shape index values often

correlate with values of flakiness index (BS EN 933-3) Page 23 of 55


Shell content of coarse aggregates (EN 933-7)

The shell content shall be declared in accordance with relevant category

specified in Table 10 according to the particular application or end use

Table 10 – Category for maximum values of shell content of coarse aggregates

Shell content - % by mass Category - SC PD 6682-1:2002 Clause 3.2.5

10

> 10

SC10

SCDeclared BS 882 limits set at 20% by mass for fractions of 10

mm and/or 8% for by mass for fractions of > 10 mm No requirement SCNR

Fines content

Fines content in EN 12620 relates to percentage passing 0.063 mm sieve

whereas in BS 882, 0.075 mm sieve is specified

PD 6682-1:2002 Table 4 – Recommended BS EN 12620 categories for fines content

Aggregate type BS 882 limits – % by mass Recommended BS EN category

Uncrushed, partially crushed or

crushed gravel coarse aggregate

Crushed rock coarse aggregate

2

4

f1.5

f4

Uncrushed, partially crushed or

crushed gravel sand

Crushed rock sand

4

16(9 for heavy duty floor finishes)

f3

f16(f10 for heavy duty floor finishes)

Gravel all-in aggregate

Crushed rock all-in aggregate

3

11

f3

f11

Page 24 of 55


Fine aggregates shall comply with the general grading requirements specified in Table 2

appropriate to their upper sieve size D

Example : fine aggregate 0/4 (d = 0 and D = 4)

Table 2 – General grading requirements

For D 4 mm and d = 0 mm

Percentage passing by mass Category

G 2 D (8) 1,4 Da (5,6) D (4) d (0) d/2 (0)

100 95 to 100 85 to 100 - - GF 85

Fine aggregates in regular satisfactory use for most applications shall comply with the

requirements specified in Table 4. When specified for special uses and cases where the

variability of grading is reduced, the grading tolerances shall be applied in accordance with

annex C (normative)

Table 4 – Tolerances on producer’s declared typical grading for general use fine aggregates

Sieve size

mm

Tolerances in percentages passing by mass

0/4 0/2 0/1

4

2

1

0,250

0,063b

5 a

-

20

20

3

-

5 a

20

25

5

-

-

5 a

25

5

a Tolerances of 5 are further limited by the requirements for the percentage passing D in Table 2 b In addition to the tolerances stated the maximum value of the fines content for the category selected in

Table 11 applies for the percentage passing the 0,063 mm sieve.

Page 25 of 55


AGGREGATES

◊ BS EN 12620:2002 Aggregates for concrete, Annex B (informative)

Guidance on the description of coarseness/fineness of fine aggregates

Either Table B.1 or Table B.2, but not both can be used

C = coarse, M = medium and F = fine (Note: some overlap of ranges)

P = percentage passing 0,5000 mm sieve

F = fineness modulus, FM = sum of cumulative percentages by mass

retained on sieves as indicated and expressed as a percentage:

FM = {(> 4) + (> 2) + (> 1) + (> 0,5) + (> 0,25) + (> 0,125)}/100

Table B.1 Coarseness or fineness based on percentage passing 0,500 mm sieve

Table B.2 Coarseness or fineness based on fineness modulus


CP MP FP

5 to 45 30 to 70 55 to 100

Fineness modulus

CF MF FF

4,0 to 2,4 2,8 to 1,5 2,1 to 0,6 Page 26 of 55


PD 6682-2:2002, Annex D (informative)

Recommended BS EN 12620 overall grading limits for fine aggregates

Table D.1 Overall grading limits for fine aggregates classified by BS EN 12620

category GF85

Sieve size

mm

Percentage by mass passing ISO 565 sieve for fine aggregate size (d/D)

0/4 (CP)a 0/4 (MP)a 0/2 (MP)a 0/2 (FP)a 0/1 (FP)a

8 100 100 - - -

6.3 95 to 100 95 to 100 - - -

4 85 to 99b (5) 85 to 99 (5) 100 100 -

2.8 - - 95 to 100 95 to 100 -

2 - - 85 to 99 (5) 85 to 99 (5) 100

1 (20) (20) (20) (20) 85 to 99 (5)

0.5 5 to 45 30 to 70 30 to 70 55 to 100 55 to 100

0.250 (20) (20) (25) (25) (25)

0.063 (3) (3) (5) (5) (5)

Note: The producer should document and, on request, declare the typical grading for which

the required tolerances are given in brackets (from Table 4, EN 12620) a Category GF85 b The inclusion of 99% in lieu of 100 % is to ensure consistency and to prevent smaller size

aggregate being classified as D sized aggregate

Page 27 of 55

Examples of Fine Aggregate Grading

Sieve size Mass retained

(g)

% retained

(by mass)

Cumulative %

retained

Cumulative %

passing

4 mm 9 2 2 98 (85 to 99 ± 5)

2 mm 46 9 11 89

1 mm 97 19 30 70

0.5 mm 99 20 50 50 (30 to 70)

0.25 mm 120 24 74 26

0.125 mm 91 18 92 8

Total sample 500 = 259

Fineness modulus = 259/100 = 2.59, (CF) or (MF)

% passing 0.5 mm sieve = 50, (MP)

0/4 (MP), Category GF85, limits shown in RED

Page 28 of 55


Fines content to be declared in accordance with EN 933-1 (0.063 mm rather than 0.075 mm)

Table 11 – Categories for maximum values of fines content

Aggregate 0,063 mm sieve


Category

f

Coarse aggregate ≤ 1,5

≤ 4

> 4

f1,5

f4

fDeclared

No requirement fNR

Natural graded 0/8 mm aggregate ≤ 3

≤ 10

≤ 16

> 16

f3

f10

f16

fDeclared

No requirement fNR

All – in aggregate ≤ 3

≤ 11

> 11

f3

f11

fDeclared

No requirement fNR

Fine aggregate ≤ 3

≤ 10

≤ 16

≤ 22

> 22

f3

f10

f16

f22

fDeclared

No requirement fNR

Page 29 of 55


Fines Quality (Annex D – normative)

Fines shall be considered non-harmful when any of the four following

conditions apply:

(a) the total fines content of the fine aggregate is less than 3% or

other value according to the provisions valid in the place of use of

the aggregate;

(b) the sand equivalent value (SE) when tested in accordance with

EN 933-8 exceeds a specified lower limit;

(c) the methylene blue test (MB) when test in accordance with

EN 933-9 gives a value less than a particular specified limit;

(d) equivalence of performance with known satisfactory aggregate is

established or there is evidence of satisfactory use with no

experience of problems.

Compliance requirements for (b) and (c) on 0/2 mm fraction shall

normally be expressed with a probability of 90%. Precise limits

not yet fixed until further evidence on use is available.

PD 6682-1:2002 recommendation: conditions (a) or (d) preferred Page 30 of 55


Physical Requirements – Clause

The necessity for testing and declaring all properties specified shall be limited

according to the particular application at end use or origin of the aggregate.

When required, the tests specified shall be carried out to determine appropriate

physical properties.

(Guidance on selection of appropriate categories for specific applications can

be found in national provisions in the place of use of the aggregate, e.g.

PD 6682-1:2003 and PD 6682-9:2003)

PD 6682-1:2003 Aggregates – Part 1: Aggregates for concrete – Guidance on the

use of BS EN 12620

The grading of coarse and fine aggregates in BS EN 12620 is based on different

principles to BS 882.

BS EN 12620 specifies grades in terms of consistency of coarse aggregate with

supplier declaring typical grading for the aggregate and working to tolerances

given in BS EN 12620.

Table 1 lists established BS aggregates for concrete and their equivalent in EN

Annex C, Annex D and Annex E detail grading requirements of BS EN 12620 for

coarse, fine and all-in aggregates.

PD 6682-9:2003 Aggregates – Part 9: Guidance on the use of European test

method standards

Page 31 of 55


Particle density and water absorption (EN 1097-6) – declared on request stating means of determination and calculations used

Bulk density (EN 1097-3) – declared on request

DURABILITY

Freeze/thaw resistance of coarse aggregates (EN 1367-1 or EN 1367-2)

If required for used in environment subject to freezing and thawing

Volume stability – drying shrinkage (EN 1367-4)

Where disruptive shrinkage cracking of concrete occurs due to properties of aggregate, when required, not exceed 0.075%

♦ Alkali-silica reactivity

When required assess in accordance with provisions valid in the place of use and results declared

(Guidance – Annex G, BS 8500-2:2006: guidance set out in BRE Digest 330)

[BS 8500-1:2006, Clause A.8.1: “If the producer follows the guidance given in BRE Digest 330, this will be deemed to have satisfied the requirement to minimize damaging alkali-silica reaction.”]

Page 32 of 55


Chemical Requirements – Clause 6

The necessity for testing and declaring all properties specified in this clause

shall be limited according to the particular application at end use or

origin of the aggregate. When required, determine appropriate chemical

properties

Chlorides (water-soluble chloride – EN 1744-1:1998, Clause 7)

On request, declared by producer ( 0.01%, use 0.01%)

Sulfur containing compounds

Acid-soluble sulfate (EN 1744-1:1998, Clause 12)

When required, declare in accordance with relevant category specified in

Table 20 – Categories for maximum values of acid-soluble sulfate content

Aggregate Acid-soluble sulfate content

Percentage by mass

Category

AS

Aggregates other than air-cooled

blastfurnace slag

0.2

0.8

> 0.8

AS0.2

AS0.8

ASDeclared

No requirement ASNR

Air-cooled blastfurnace slag

1.0

> 1.0

AS1.0

ASDeclared

No requirement ASNR Page 33 of 55


Alkali – silica reactivity

“In accordance with provisions valid in place of use”

UK – BS 8500-2:2006

Clause 12.3 Conformity criteria for properties other than strength

“The risk of damaging alkali-silica reaction shall be deemed to be

minimized if the concrete conforms to the guidance in BRE Digest 330.”

BRE Digest 330, Alkali-silica reaction in concrete

Part 1: Background to the guidance notes, 2004

Part 2: Detailed guidance for new construction, 2004

Part 3: Worked examples, 2004

Part 4: Simplified guidance for new construction using aggregates of

normal reactivity, 2004

All aggregates assumed to be of normal reactivity unless otherwise

determined by BS 812: Part 123 concrete prism method

(expansion at 12 months) as (low, normal or high reactivity)

BS 812: Part 104 petrographic examination (qualitative & quantitative) Page 34 of 55


BRE Digest 330 Part 2 Table 1 shows the recommended limits for alkali contents of concrete

Aggregate type

or

combinations

Alkali content of the CEM I-type component of the cement

or the CEM I component of a combination with ggbs or pfa

Low alkali

(guaranteed ≤ 0.60% Na2O eq

on spot samples)

Moderate alkali

(declared mean

≤ 0.75% Na2O eq)

High alkali

(declared mean

> 0.75% Na2O eq)

Low reactivity Self-limiting:

no mix calculation

Self-limiting:

no mix calculation

Limit:

≤ 5.0 kg Na2O eq/m3

Normal

reactivity

Self-limiting:

no mix calculation

Limit:


Limit:


High reactivity Limit:


Limit:


Limit:


BRE Digest 330 Part 2 Table 5

Classification of cement based on the alkali content of the CEM I-type component

Cement classification Alkali limit

Low alkali cement Cement with a guaranteed alkali content 0.60% Na2O eq

Moderate alkali cement Cement with an alkali content 0.75% Na2O eq based on

manufacturer’s declared mean

High alkali cement Cement with an alkali content > 0.75% Na2O eq based on

manufacturer’s declared mean

Page 35 of 55


BS 812-123:1999 Method for determination of alkali-silica reactivity – concrete prism method

Suggested criteria for interpretation: applies to low and normal reactivity UK aggregates

(BSI Working Group B/502/6/10) Expansion for up to 12 months

%

Classification for aggregate

combination tested

Aggregate type from Table 1

> 0.20 Expansive Normal reactivity

0.10 to 0.20 Possibly expansive Normal reactivity

> 0.05 to 0.10 0.05 Probably non-expansive Low reactivity

0.05 Non-expansive Low reactivity

Specific combinations of aggregates in mix for a particular construction with cement and

water or as given in Table 1 – Mix proportions by volume for cement and dry aggregates

Material Proportion - % by volume

Cement * 22.2

Coarse aggregates

< 10 mm

> 10 mm

22.0

16.5

Fine aggregates 16.5

Water (free) 22.8

* Add potassium sulfate to mixing water to produce the same alkalinity as a mix with

cement having alkali content (1.00 0.05%) sodium oxide equivalent

Page 36 of 55


BS 812 – Part 104: 1994 Method for qualitative and quantitative petrographic

examination of aggregates

Principle

The method involves the visual recognition and quantification of rock and

mineral constituents of an aggregate sample to determine the petrographic

composition.

Methods are given to quantify the petrographic composition of the aggregate

sample. These procedures allow for the thorough and statistically reliable

petrographic examination of an aggregate sample

Report : a summary of the results of the quantitative examination, giving the

method of determination, the constituent proportions and 95% confidence

limits for the constituent proportions (rounded to nearest 1%) and the 95%

confidence limits to nearest 0.1%

Table 1 Minimum size of laboratory sample

Maximum particle size – mm Minimum mass - kg

50

40

20

10

200

100

13

2 Page 37 of 55


BS 7943-1999 Guide to the interpretation of petrographical examinations for alkali-silica reactivity

Aggregate – classified as low, normal or high reactivity based on petrographic composition. Aggregates containing detectable amounts of opal or opaline silica are not classified and should not be used in concrete as they are the most reactive of the mineral constituents from the point of view of ASR:

(a) opal or opaline silica;

(b) tridymite;

(c) cristobalite;

(d) quartz with crystal dislocations;

(e) microcrystalline quartz;

(f) highly strained quartz;

(g) volcanic glass

Table 1 Guidance on rock types – with suggested reactivity level (L, N or H) and indicating damage attributed in UK practice (none, some evidence or reaction, but no reported damage, reaction but uncertainty whether damage has resulted and reaction and resulting damage – ranging from superficial cracking to damage of greater significance)

Table 2 Guidance on mineral types – indicating damage attributed in UK practice (as above)

Page 38 of 55


ASTM C295 Standard guide for petrographic examination of aggregates for concrete

Alternative for BS 812 – Part 104: 1994 Method for qualitative and quantitative petrographic examination of aggregates, but does not have corresponding guidance for the interpretation of petrographical examinations for alkali-silica reactivity as BS 7943-1999 Guide to the interpretation of petrographical examinations for alkali-silica reactivity

ASTM C1260 Standard test method for potential alkali reactivity of aggregates (mortar-bar method)

Accelerated test by exposing specimens to NaOH (1N) solution for 14 days

Expansions of less than 0.10% at 16 days after casting – innocuous behaviour

Expansions of more than 0.10% at 16 days after casting – potentially deleterious

Expansions between 0.10% and 0.20% at 16 days after casting – include both aggregates that are known to be innocuous and deleterious in field performance.

Supplementary test: ASTM C295 or ASTM C856 Standard Practice for petrographic examination of hardened concrete (to identify alkali-silica reaction)

ASTM C1293 Standard test method for determining length change of concrete due to alkali-silica reaction

similar to BS 812 Part 123 but different in some details, e.g. lower alkali content used

Page 39 of 55


Sulfur containing compounds

Total sulfur (EN 1744-1:1998, Clause 11)

When required, shall not exceed:

(a) 2% S by mass for air-cooled blastfurnace slag;

(b) 1% S by mass for aggregates other than air-cooled blastfurnace slag

If pyrrhotite is present, maximum total sulfur content = 0.1% S

Constituents which alter rate of setting and hardening of concrete (EN 1744-1:

1998, Clause 15.3)

Proportion of organic or other substances that alter rate of setting and

hardening of concrete shall not:

(a) increase stiffening time of mortar test specimens by more than

120 min.

(b) decrease compressive strength of mortar test specimens by more

than 20% at 28 days

Organic component – EN 1744-1:1998, Clause 15.1

Fulvo acid content – EN 1744-1:1998, Clause 15.2

Constituents which affect volume stability of air-cooled blastfurnace slag

Free from dicalcium silicate disintegration (EN 1744-1:1998, Clause 19.1)

Free from iron disintegration (EN 1744-1:1998, Clause 19.2) Page 40 of 55


Carbonate content of fine aggregates for concrete pavement surface courses

When required to control carbonate content in fine aggregates, determine as specified in EN 196-21:1989, Clause 5, with test portion prepared in accordance with EN 1744-1:1998, Clause 12.3 and declared.

EVALUATION OF CONFORMITY

Producer shall undertake initial test and factory production control to ensure that the product conforms to this standard and to declared values as appropriate

Initial type tests

(a) a new source of aggregate to be used (to characterize properties)

(b) there is a major change in the nature of the raw material or in the processing conditions which may affect the properties of the aggregates

Factory production control – Annex H (normative)

Table H.1 – Minimum test frequencies for general purpose

Table H.2 – Minimum test frequencies for properties specific to end use

Table H.3 – Minimum test frequencies for properties appropriate to aggregate from particular source

[monitoring conformity with relevant requirements and declared values] Page 41 of 55


Annex ZZA (normative)

Testing scheme for aggregates imported from

sources/quarries without a system of product quality control

(to be undertaken by importers of aggregates)

Table ZZA.1 Minimum test frequencies for general properties

Table ZZA.2 Minimum test frequencies for properties specific

to end use

Table ZZA.3 Minimum test frequencies for properties

appropriate to aggregates from particular sources/quarries

The above Tables are similar in requirements to Table H.1,

Table H.2 and Table H.3 for Factory production control in

Annex H (normative) of SS EN 12620 : 2008

[For details of these Annexes – see SS EN 12620: 2008]

Page 42 of 55


Recycling for Sustainable Construction

Recycled Aggregate

Drive for sustainable construction to promote its use

Carbon footprint – cement (0.8 to 1.0 tonne CO2/tonne)

– new aggregate (0.003 tonne CO2/tonne)

– RCA (< 0.003 tonne CO2/tonne)

Cost of producing recycled aggregate by conventional means of thermal decomposition of cement is high

Lack of technical guidance hinders its use in concrete specifications

Reluctance in acceptance may be overcome by incentive

to use recycled aggregates (Green Building Award)

Page 43 of 55


Recycled Aggregate

EN 12620:2002 defines recycled aggregate as aggregate

resulting from the processing of inorganic material

previously used in construction

REUSE

EN 206-1:2000 subclause 5.2.3.3 Recovered aggregate

Aggregate recovered from wash water or fresh concrete

may be used as aggregate for concrete

Limit – not greater than 5% of total aggregate for undivided

recovered aggregate

For greater then 5% – shall be of same type as primary

aggregate and divided into separate coarse and fine

fraction and conform to EN 12620

[ISO 22965-2:2007 : similar limits for recovered aggregate] Page 44 of 55


Classification of the constituents of coarse recycled aggregates

Constituent Description

Rc Concrete, concrete products, mortar

Concrete masonry units

Ru Unbound aggregate, natural stone

Hydraulically bound aggregate

Rb Clay masonry units (i.e. bricks and tiles)

Calcium silicate masonry units

Aerated non-floating concrete

Ra Bituminous materials

FL Floating materials in volume

X

Rg

Others:

Cohesive (i.e. clay and soil)

Miscellaneous: metals (ferrous and non ferrous)

Non-floating wood, plastic and rubber

Gypsum plaster

Glass Page 45 of 55


Classification of the constituents of coarse recycled aggregates Table 20 – Categories for constituents of coarse recycled aggregates

Constituent Content – Percentage by mass Category

Rc 90

80

70

50

< 50

Rc 90

Rc 80

Rc 70

Rc 50

Rc Declared

No requirement Rc NR

Rc + Ru 90

80

70

50

< 50

Rcu 90

Rcu 80

Rcu 70

Rcu 50

Rcu Declared

No requirement Rcu NR

Rb

10

30

50

> 50

Rb 10-

Rb 30-

Rb 50-

Rb Declared

No requirement Rb NR

Ra 1

5

10

Ra 1-

Ra 5-

Ra 10-

X + Rg 0.5

1

2

XRg 0.5-

XRg 5-

XRg 5-

Content – cm3 / kg

FL 0.2

2

5

FL 0.2-

FL 2-

FL 5-

Page 46 of 55


Recycled Aggregate BS 8500-2:2006 subclause 4.3 Aggregates(SS 544-2: 2009)

Coarse recycled concrete aggregate (RCA)

Coarse recycled aggregate (RA)

Requirements specified in Table 2 (mass fraction – %)

Type of

aggregate

Maximum

masonry

content

Maximum

fines

Maximum

lightweight

material B)

Maximum

asphalt

Maximum other foreign

material e.g. glass,

plastics, metals

Maximum

acid – soluble

sulfate (SO3)

RCA A),C) 5 5 0,5 5,0 1,0 1,0

RA 100 3 1,0 10,0 1,0 - D)

A) Where the material to be used is obtained by crushing hardened concrete of known composition that

has not been in use, e.g. surplus precast units or returned fresh concrete, and not contaminated during

storage and processing, the only requirements are those for grading and maximum fines B) Material with a density less than 1 000 kg/m3

C) The provisions for coarse RCA may be applied to mixtures of natural coarse aggregates blended with

the listed constituents D) The appropriate limit and test method needs to be determined on a case-by-case basis (see Note 6 to

4.3)

[SS 544-2: 2009 – Singapore equivalent to BS 8500-2: 2006] Page 47 of 55


Recycled Aggregate

BS 8500-2:2006 subclause 4.3 Aggregates

Note 6 (continued)

In particular the project specification should include:

maximum acid-soluble sulfate;

method for determination of the chloride content;

classification with respect to alkali-aggregate

reactivity;

method for determination of the alkali content;

any limitations on use of concrete

[SS 544-2: 2009 – Singapore equivalent to BS 8500-2: 2006 ] Page 48 of 55


Recycled Aggregate


Note 6 : Provisions for the use of fine RCA and fine RA

are not given in BS 8500 but this does not preclude

their use where it is determined that, due to the source

of materials, significant quantities of deleterious

materials are not present and their use has been

agreed.

While some requirements for coarse RA are specified,

they are insufficient to form an adequate specification.

As the potential composition of RA is so wide, the

additional specification requirements should be

assessed on a case-by-case basis taking into account

the specific composition of the RA. [SS 544-2: 2009 – Singapore equivalent to BS 8500-2: 2006]

Page 49 of 55


Recycled Aggregate


When the composition of coarse RCA and coarse RA is tested in accordance with Annex B (normative), the test results for each type of aggregate shall not exceed the maximum value specified in Table 2

Composites of coarse RCA or coarse RA and natural aggregates shall conform to the general requirements for aggregates specified in BS EN 12620 as appropriate and to the general requirements specified in this subclause

This provides a way to bring RCA or RA within the limits of Table 2 by the inclusion of original natural aggregates that are much below the limits.

[SS 544-2: 2009 – Singapore equivalent to BS 8500-2: 2006]

Page 50 of 55


Recycled Aggregate

BS 8500-2:2006 subclause 4.3 Aggregates Table 3 Limitations on the use of coarse RCA Maximum strength class A) : C40/50 A) material obtained by crushing hardened concrete of known composition that has not been in use and not contaminated during storage and processing may be used in any strength class

Exposure classes B): XO (no risk of corrosion attack) XC1 to XC4 (corrosion induced by carbonation) XF1 (Freeze/thaw attack, moderate water saturation, without de-icing agent DC-1 (sulfate at low levels) B) These aggregates may be used in other exposure classes provided it has been demonstrated that the resulting concrete is suitable for the intended environment.

Note: No limitation on percentage to be used – depends on performance

[RCA limited to 20% replacement for designated concrete – 6.2.2] [BCA Regulation limits the use of RCA up to 20 % replacement only] [In addition, up to 10% washed copper slag replacement for sand] Page 51 of 55


Use of Washed Copper Slag in Concrete

Copper slag that has been used in sand blasting and then washed

to remove contaminants (rust, paint, sulfate and chloride)

BCA Regulation

Up to 10% by mass of fine aggregate for structural concrete

No limit for non-structural concrete

Sulfate content and chloride content need to be monitored by

producer and declared

Suggested Guideline

As for coarse RCA, acid soluble chloride: 1% by mass

(Test method: EN 1744-5, Test for chemical properties of aggregate,

Part 5: Determination of acid soluble chloride salts)

Table 21 acid soluble sulfate 0.8% by mass

(Test method: EN 1744-1: Test for chemical properties of aggregate,

Part 1: Chemical analysis, Clause 11) Page 52 of 55

Recycled Concrete Aggregates – The Microwave Beneficiation Option

Ong et al, K.C.G. Ong, A. Akbarnezhad Zhang M. H., Tam C. T., T. W. J. Foo

Prof S L Lee Symposium, Singapore, April 2011

Fig.1. Various types of RCA comprising (a) a granite particle surrounded by

adhering mortar, (b) three granite particles held together and surrounded by

mortar, (c) only mortar

Fig.6. Surface of a RCA particle before and after microwave heating Page 53 of 55

Fig.2. Relationship between

adhering mortar content (by mass)

and water absorption

[Attached mortar expected to lower

concrete strength and modulus of

elasticity unless mortar content in

concrete is reduced by the likely amount of attached mortar in RCA]

Fig.3. Relationship between

adhering mortar content (by mass)

and bulk specific density

Recycled Concrete Aggregates – The Microwave Beneficiation Option

Ong et al, K.C.G. Ong, A. Akbarnezhad Zhang M. H., Tam C. T., T. W. J. Foo

Prof S L Lee Symposium, Singapore, April 2011

Page 54 of 55


References

PD 6682-1:2003 Aggregates – Part 1: Aggregates for concrete –

Guidance on the use of BS EN 12620

PD 6682-9:2003 Aggregates – Part 9: Guidance on the use of European

test method standards

BRE Digest 330, Alkali-silica reaction in concrete

Part 1: Background to the guidance notes, 2004

Part 2: Detailed guidance for new construction, 2004

Part 3: Worked examples, 2004

Part 4: Simplified guidance for new construction using aggregates

of normal reactivity, 2004

BS 7943-1999 Guide to the interpretation of petrographical examinations

for alkali-silica reactivity

Page 55 of 55

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5-Constituents Materials for Concrete â€“ Aggregates

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