22
Characterization and evaluation of rendering mortars and basecoat mortars for ETICS with CSA and Portland cement Extended Abstract Tiago Manuel Pereira da Mota dos Santos Trigo July 2014
Characterization and evaluation of rendering mortars and basecoat
mortars for ETICS with CSA and Portland cement
Extended Abstract
Tiago Manuel Pereira da Mota dos Santos Trigo
July 2014
1
1 Introduction
Portland cement was first developed approximately 175 years ago. Since then, it has been largely
used in construction, as the primary binder in concrete production, and assumed to be a standard
binder, with good durability, versatility and great economic value (Juenger et al., 2011).
Even though there are economic advantages to the use of Portland cement, there are negative
environmental consequences, and thus great pressure has been put on the cement industry to reduce
energy usage in Portland cement production and to reduce gas emissions. Currently, 5% of the CO2
gas emissions are due to the cement industry. Every year, roughly 2 billion tons of CO2 are produced,
and for each ton of Portland cement produced, 0.87 tons of CO2 are released into the atmosphere. It is
estimated that by 2025 the annual production will reach 3.5 billion tons; these numbers are equivalent
to the current total CO2 gas emission across Europe, which includes the entire industry and transports.
The production of this binder consumes between 10-11 EJ per year, approximately 2 to 3% of the
primary energy consumption (Alaqui et al.; 2007; Juenger et al., 2011).
There are two other problems related to the use of Portland cement: shrinkage, which can lead to the
cracking of elements, and setting time, thus not allowing for a rapid setting. In situations that require a
quick setting of materials and a high early strength, this type of cement is not a good solution. For
instance, the repair of concrete pavements and bridge decks requires materials that can be rapidly
placed and cured in order to be open to traffic in a relatively short period of time. Furthermore, the
Portland cement has durability problems, particularly in aggressive environments, such as areas with
high acidity or sulfates concentration, which can cause the degradation of this cement (Juenger et al.,
2011).
Due to these issues, there is an arising need to find new alternatives to this binder. The cement
industry has to solve issues such as the previously referenced in order to protect the environment and
promote a sustainable development. Thus, the industry will have to reduce gas emissions and find
solutions that would allow lower energy consumption. Moreover, there is a need to increase the
performance, especially in terms of durability, setting times and shrinkage.
Following research for new alternatives, the calcium sulfoaluminate cement (CSA) has been
presenting very interesting characteristics, and has been proposed as a possible alternative to
Portland cement (Juenger et al., 2011; Shi et al., 2011;).
Calcium sulfoaluminate cements(CSA) were developed by the China Building Materials Academy in
the 1970s, with the intention of manufacturing self-stressed concrete pipes to capitalise on the
expansive properties of this material (Shi et al., 2011). Thus, CSA cements have been used in China
as a binder for concrete in bridges, concrete pipes, precast concrete, prestressed concrete elements,
low temperature construction and shotcrete. This cement and the ferroaluminate cement are known as
The Third Cement Series in China, characterized by having large amounts of Ye'elimite (C4A3Ŝ). The
Ye'elimite was introduced as a cementitious phase in the 1960s, when it was patented by Alexander
2
Klein as an expansive or shrinkage compensating addition to cementitious binders (Juenger et al.,
2011; Chen, 2009).
In addition to Ye'elimite, the calcium sulfoaluminate clinker is composed by dicalcium silicate (C2S),
calcium aluminoferrite (C4AF) and calcium sulfates (CS e CS H2). The calcium sulfates can either be
formed as anhydrite in clinker or be interground as plaster after clinkering, or the combination of the
two (Glasser and Zhang, 2001 citado por Chen, 2009).
The sulfoaluminate clinker is produced from limestone, bauxite and calcium sulfate. The production
temperatures of this clinker are situated between 1200-1300ºC, about 200ºC lower than the
temperature used for Portland cement production, resulting in lower energy consumption (Shi et al.,
2011).
The CSA cement uses Ye'elimite as an early strength gain phase, instead of the tricalcium silicate
(C3S) used in Portland cement, and the dicalcium silicate (C2S) for developing these long-term
strengths. Through these steps, which use less calcium oxide (CaO) in the C3S, there is a reduction in
carbon dioxide (CO2) emissions during the calcination of limestone in cement kilns (Chen et al., 2012).
The amount of lime (CaO) required for the production of CSA cement is considerably smaller than that
required for Portland cement. The specific amount of lime needed for the synthesis of Ye'elimite
(C4A3Ŝ) is 50%, 56%, 59% and 80% of the quantity necessary for the formation of the respective C3S,
C2S, C3A (tricalcium aluminate) and C4AF hydration reactions in Portland cement production. Due to
the lower amount of limestone and the lower fuel consumption, the CO2 emissions are reduced to
about half of that emitted by Portland cement clinker production (Juenger et al, 2011; Shi et al, 2011).
In addition to these factors, and due to high porosity, since the clinker is more porous than the
Portland cement, the energy required for its crushing is reduced (Chen et al., 2012). The disadvantage
of the production of calcium sulfoaluminate clinker in relation to the Portland cement is related to the
higher cost associated to it. A bag of this cement can cost twice as much as the same amount of
Portland cement. This situation is logically due to the current domain of Portland cement, which is
produced in enormous quantities, so it will, obviously, be the cheapest (CCTI, 2008).
To obtain CSA cement it is needed to add a source of calcium sulfate, generally gypsum. Usually,
adding 15 to 25% of this element allows for a good setting time, strength development and good
volume stability, yielding the CSA Quick (Angulski da Luz, 2005).
The hydration reactions of Ye'elimite with calcium sulfates start-up quickly and give rise to ettringite
(C6AŜ3H32) and gibbsite (AH3), responsible for the development of CSA cement's early strength
(Chen, 2009). The ettringite is a crystalline substance that occupies twice the volume of the original
compound, when expanded. Equations 1.1 and 1.2 show, respectively, the processes of Ye'elimite
hydration in the absence and presence of calcium hydroxide.
C4A3Ŝ +2CŜH2+34H→ C6AŜ3H32+ 2AH3 Equation 1.1
3
C4A3Ŝ +8CŜH2+ 6CH + 74H→3C6AŜ3H32 Equation 1.2
When the ettringite is formed in the absence of calcium hydroxide, it does not have expansion
properties and provides high early strength. When the formation is according to equation 1.2, the
formed ettringite is expansive; this behavior can be exploited for the production of special binders,
resistant to shrinkage or prestressing (Shi et al., 2011). The presence of calcium hydroxide (CH) could
be originated from the hydration of free lime or dicalcium silicate. According to Min and Mingshu
(1994, cited by Angulski da Luz, 2005), if the calcium hydroxide is placed in a non-saturated solution,
the formed ettringite does not expand, thus contributing to the mortar strength. Also according to this
author, the expansive ettringite formation will depend not only on the presence of lime, but also the
medium alkalinity (Angulski Light, 2005; Chen, 2009). The expansion in CSA cements can also be due
to the amount of C4A3Ŝ, water cement ratio, sulfate amount and the fineness of the particles (Chen et
al., 2012). CSA cements show a rapid setting time, high early strengths, and compensating shrinkage,
due to the C4A3Ŝ rapid reaction and to the natural expansion of ettringite.
These cements have received special attention, because relatively to Portland cement they have
some advantages, such as (Juenger et al.,2011; Shi et al., 2011; CCTI, 2008; Alaqui et al.; 2007):
Producing approximately half of CO2 emissions;
Exhibiting temperatures of clinker production between 1200-1300 ° C, 200 °C to less;
Get a clinker more easier to grind, which means there is less energy consumption;
Allow rapid setting times, reaching higher strengths in shorter times;
Better application at low temperatures, has higher strength in less time;
Exhibiting lower pH (10-11), which is important when concrete or cement is exposed to
moisture;
Low shrinkage;
Low porosity;
High resistance to sulfates.
The low shrinkage of CSA cements is due to two reasons. The first reason is that they consume more
hydration water than Portland cement; most of the mixing water is consumed for hydration which
results in less excess water available to drying, and consequently, tendency for shrinkage. CSA
cements require about 50% more water compared to Portland cements for a better hydration than
these. The other explanation is that these cements gain strength rapidly, and thus the resistance
increases more rapidly than the tension of retraction, which avoids the shrinkage cracks (CCTI, 2008).
Moreover, the CSA cements have some uncertainty, such as their durability, their use in moist
environments, their sulfate richness and their expansive behavior. Regarding to durability, this is not
well determined in the long term, which means that there is a need for more research. Relatively to its
use in wet environments, the uncertainty has to do with the fact that CSA cements having gypsum in
their constitution, since it can cause overexpansion. The expansive behavior caused by the effect of
4
ettringite can't always be taken as an advantage and may have a negative effect on elements where
the CSA cement is used (Juenger et al., 2011).
CSA cement, because of its low pH, rapid strength, lower energy costs and lower emissions, exhibits
an interesting solution that can be advantageous when mixed with Portland cement.
2 Experimental study
The present study aims at the characterization and evaluation of mortars with Portland and calcium
sulfoaluminate (CSA) binders. Starting from industrial mortars sought to replace Portland cement by
CSA cement in various amounts. The incorporation of this binder was made in rendering mortars and
basecoat mortars for ETICS (External Thermal Insulation Composite Systems), thereby dividing the
experimental campaign into two.
In the rendering mortars was introduced a smaller amount of total binder (12,5-14 %), because these
mortars are applied in thick layers (10-20 mm) and in order to minimize shrinkage. In the basecoat
mortars was intended to produce mortars with a higher strength and adhesion that are applied in thin
layers (2-5 mm), thus was introduced a bigger amount of binder (about 20 % more).
For both products were produced reference mortars, with just Portland cement or just CSA cement,
and mortars with both binders in different amounts. For the evaluation of both products a battery of
tests was performed on the mortars in fresh and hardened state. The tests, in general, are common to
the two products, differing only some tests that are more justified for the concerned product. This
battery of tests allowed making a general characterization of 4 mortars by product type. The mortars
mixtures can be found in table 1.
The results analysis consisted in comparing the results between the mortars of the same product and
comparing the results of both products, with the following objectives:
Determine the influence of CSA cement and the effect of the introduced amount, on the
properties of cement mortars in fresh and hardened state, with particular relevance to the
setting time and shrinkage;
Evaluate the behaviour of mortars produced under various curing conditions (normal, heat,
water immersion) as well as their durability (freeze-thaw);
Evaluate the relationship between the two binders, Portland and CSA cement, at the level of
its impact on the final properties of the mortars;
Evaluate the potential of the CSA cement introduction in the mortars application.
5
Table 1 – General characterization of mortar mixtures used in experimental campaigns (% in mass)
Rendering mortars Basecoat mortars for ETICS
Materials Type ROP R+OP:CSA ROP:+CSA RCSA BOP B+OP:CSA BOP:+CSA BCSA
Cement type I
Binder
- 28-36% 18-26% 6-14% 0%
Cement type II 10-15% 8-13% 2-6% 0% -
CSA Cement 0% 2-4% 8-12% 10-15% 0% 6-14% 18-26% 28-36%
Silica sand Aggregate Adjustment
Water repellent
Admixture
0,2-0,8%
Water retention and plasticising admixture
0,08-0,10% 0,20-0,40%
Setting time accelerator 0-0,05% 0-0,10%
Setting time retarder 0-0,10%
Filler Additive 10-20% -
Plastic fibers Additive - 0,05-0,15%
Mortar characteristics
Water/cement ratio
-
1,45 1,4 1,55 1,5 0,85 0,85 0,85 0,9
Ponderal ratios Portland:CSA:Sand
00:05,7 1:0,4:7,02 1:2,5:17,59 01:05,8 1:2,14:8,91 00:02,1 1:0,45:3,05 1:2,2:6,71
ROP: mortar with just Portland cement; R+OP:CSA: mortar with both binders, but with the Portland cement with more amount; ROP:+CSA: mortar with both binders, but with the CSA cement with more
amount; RCSA: mortar with just CSA cement;
BOP: : mortar with just Portland cement; B+OP:CSA: mortar with both binders, but with the Portland cement with more amount; BOP:+CSA: mortar with both binders, but with the CSA cement with more
amount; BCSA: mortar with just CSA cement.
6
The table 2 presents the tests in fresh and hardened state per product and the respective standards or
test procedures.
Table 2 – Tests performed in experimental campaign
Characterization Test Standard Product
Fresh state properties
Consistence (flow value) EN 1015-3 (1999)
Rendering mortar
and Basecoat
mortar
Bulk density EN 1015-6 (1998)
Setting time EN NP 196-3 (2006)
Hardened state properties
Bulk density EN 1015-10 (1999)
Tensile and compressive strengths EN 1015-11 (1999)
Dimensional variation (shrinkage) and mass variation Cahier 2669-4 (1993)
Dynamic elastic modulus NF B 10-511 (1975)
Water absorption coefficient due to capillary Adapted da EN 1015-18
(2002)
Water absorption at low pressure Adapted do LNEC FE Pa
39 (2002)
Water vapor permeability EN 1015-19 (1998)
Open porosity Adapted da RILEM I.1
(1980)
Durability (freeze-thaw) Adapted da EN 1348
(2007)
Adhesive strength in brick substrate EN 1015-12 (2000) Rendering
mortar Cracking susceptibility – brick substrate Internal method
Adhesive strength in concrete and EPS substrate
EN 1348 (2007) e EN 12004 (2008) Basecoat
mortar
Impact resistance ETAG (2000)
The internal method of cracking susceptibility test consists in squirting water on the specimen,
allowing a better observation of the existence or not of cracks, their orientation, size and width.
These tests were done in various types of specimens after four types of different curing conditions:
normal conditions of temperatures and humidity, after water immersion, after heat exposition and after
freeze-thaw cycles, the last three curing conditions are referenced in the EN 1348 (CEN, 2007) and
EN 12004 (CEN, 2008) standards. The four types of curing conditions will be following presented:
i) Normal curing conditions: The normal curing conditions and humidity consists in the curing of
the specimens in a climate-controlled chamber, with a 23 ± 2 °C of temperature and 50 ± 5%
of relative humidity. The specimens remained 28 days in these conditions.
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ii) Heat curing conditions: In the conditions of heat exposition the specimens are stored in the
normal conditions for 14 days, and after that they are placed in one stove with air circulation at
70 ± 2 °C during other 14 days, followed by 1 day in normal curing conditions.
iii) Water immersion curing conditions: In the conditions after water immersion, the specimens
initially are stored for 7 days under normal conditions e then they are submerged in water at
23 ± 2 °C during 21 days.
iv) Freeze-thaw curing conditions: in the conditions after freeze-thaw cycle, the specimens, like
after water immersion curing conditions , are stored for 7 days under normal conditions and
after that they are submerged in water at 23 ± 2 °C during 21 days. After 21 days, starts the
25 cycles freeze-thaw, and each cycle consists in introduce the specimens in an ice chamber
with a -15 ± 3 °C of temperature for 4 hours. After that period the specimens are submerged in
water at 23 ± 2 °C for 4 hours. The specimens are maintained under water until the start of the
next cycle. After 25 cycles, allow the specimens reach the normal air conditions. The
Durability tests are considered the tests after freeze-thaw curing conditions.
The table 3 presents the specimens types produced for each test as well as the respective types of
curing conditions.
Table 3 – Specimens and respective curing conditions s conditions for each test
Characterization Test Test specimen type Curing
conditions
Hardened state properties
Bulk density Prismatic 25 x 25 x 280 mm3 Normal
Dynamic elastic modulus
Tensile and compressive strengths
Prismatic 40 x 40 x 160 mm3
Normal, immersion and freeze-
thaw
Dimensional variation (shrinkage) and mass variation
Water absorption coefficient due to capillary
Half’s of prismatic specimens 40 x 40 x 160 mm3
Normal
Water absorption at low pressure Circular 12 cm diameter
Water vapor permeability
Open porosity 1 cm3 cubes
Adhesive strength in brick substrate Coating layer in hollowed ceramic
bricks with 300 x 200 x 110 mm3 Cracking susceptibility – brick substrate
Adhesive strength in concrete and EPS substrate
Coating layer in concrete and EPS substrate
Normal, immersion and heat
Impact resistance Coating layer in EPS substrate with or
without reinforcement Normal
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The following table 4, presents a summary of the number of measurements made for each product, in
the fresh and hardened states.
Table 4 – Number of measurements for each product
Characterization Test Rendering mortar Basecoat mortar
Fresh state properties
Consistence (flow value) 5 4
Bulk density 5 4
Setting time 5 4
Hardened state properties
Bulk density 10 8
Tensile and compressive strengths 30 24
Dimensional variation (shrinkage) 40 32
Dynamic elastic modulus 10 8
Water absorption coefficient due to capillary
15 12
Water absorption at low pressure 5 4
Water vapor permeability 5 4
Open porosity 15 12
Adhesive strength in brick substrate 20 -
Cracking susceptibility – brick substrate
5 -
Adhesive strength in concrete and EPS substrate
- 160
Impact resistance - 16
Total measurements 170 292
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3 Results
3.1 Rendering mortars
The rendering mortars results are presented in the table 5. The tabled values are the average values
for each test.
Table 5 – Rendering mortars results
Mortar ROP R+OP:CSA ROP:+CSA RCSA
Test
Fresh state
Consistence (flow value) (mm) 150 153 130 149
Bulk density (kg/m3) 1554,4 1535,47 1492,79 1497,89
Setting time with regulators (min) 360/465 195/360 60/150 270/390
Setting time without regulators (min) 360/465 mai-30 60/150 270/390
Hardened state
Bulk density (kg/m3) 1557,97 1508,49 1572,51 1584,31
Tensile strength (MPa) 1,56 0,85 1,12 1,27
Tensile strength after water immersion curing conditions (MPa)
1,21 0,66 0,96 0,92
Compressive strength (MPa) 3,41 1,1 2,51 3,83
Compressive strength after water immersion curing conditions (MPa)
2,01 1,04 1,89 2,44
Dimensional variation (shrinkage) (mm/m)
0,99 0,76 0,87 2,23
Dimensional variation (shrinkage) after water immersion curing
conditions (mm/m) 0,49 0,08 -0,1 1,8
Mass variation (g/kg) -76,99 -82,4 -82,12 -75,57
Mass variation after water immersion curing conditions (g/kg)
25,09 -4,84 18,18 45,65
Dynamic elastic modulus (MPa) 7061,9 4886,89 5852,53 7260,44
Water absorption coefficient due to capillary (kg/(m2.min0,5)
0,07 0,02 0,03 0,03
Water absorption at low pressure (ml) 1,1 0,05 0,15 0,25
Water vapor diffusion coefficient 4,31 4,03 7,09 4,54
Open porosity (%) 42 37,37 40,1 42,51
Adhesive strength in brick substrate (MPa ) and rupture typology
0,50 (cohesive in
the rendering)
0,19 (cohesive in
the rendering)
0,13 (15% cohesive,
85% adhesive in the brick)
0,11 (adhesive in
the brick)
Cracking susceptibility – brick substrate
Not Not Not Not
Durability (after freeze-thaw curing conditions)
Dimensional variation (shrinkage) (mm/m)
0,04 -0,24 0,43 0,15
Mass variation (mm/m) -84,29 -113,36 -102,53 -99,63
Tensile bending strength (MPa) 0,91 0,51 0,78 0,69
Compressive strength (Mpa) 0,75 0,79 1,2 0,95
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It was found for the fresh state characteristics that the introduce of CSA cement provides a plastic
effect in the mortars, decreasing the setting times, 90 to 300 minutes, and the consistence, flow value,
until 15 %.
Regarding to the hardened state properties, as a bulk density, compressive strength, dynamic elastic
modulus and the open porosity, they demonstrate da same trend. When CSA cement it’s introduced
there is a decreasing of the values, however, the values increases with the increasing of this binder,
concluding that these properties depends on this two binders relation. For the bulk density, the values
of the Portland cement reference mortar are exceeded when the CSA cement amount it is higher than
the Portland, with only a 2 % variation. For the compressive strength, only the CSA cement reference
mortar demonstrates higher values than the Portland cement reference mortar. This same situation is
also observed for the dynamic elastic modulus results, with the increase of 10 %, and for the open
porosity, although with a minimum increase of just 1 %. Therefore, it is concluded that the values of
these properties increases when the CSA cement amount it is higher than the Portland amount and
decreases when the ratio is reversed.
Regarding the tensile strength, there is a decreasing of the values when CSA is introduced, between
20 and 45 %. This situation is also observed for the adhesive strength in brick substrate, where the
results values of the Portland cement reference mortar are about twice comparatively with the others.
Should be also mentioned that the rupture types of the mortars with more CSA cement are adhesive
to brick. These two situations indicate a weak internal cohesion and binding to the substrate of the
mortars with CSA cement.
For the dimensional variations (shrinkage) was observed a decrease with the introduction of CSA
cement, about 20 %, excepting the Portland cement reference mortar, that exhibits the high value.
Even repeating the test for this mortar, the results demonstrates the same results, indicating some
instability regarding the shrinkage behavior.
The water absorption coefficients due to capillary and water absorption at low pressure properties
demonstrate improvements in the results with the introduction of CSA cement. The water absorption
coefficient due to capillary decreased for the half when was introduced this binder. The water
absorption at low pressure results are even more satisfactory, because there was a decrease of more
than 75 % between the Portland cement reference mortar and the others. Relative to the water vapor
permeability results, they demonstrate a bit inconstant, just highlighting one increase of the water
vapor permeability resistance for the mortars with both binders and with the CSA cement in more
amounts.
With respect to the after water immersion results, the tensile and compressive strengths demonstrate
the same trend that after normal curing conditions. The shrinkage results were all within normal limits,
except de ROP:+CSA (mortar with both binders, but with the CSA cement with more amount) mortar,
which expanded.
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Regarding to the durability, all the mortars exhibited a deteriorated state. The same decrease of
values in the tensile bending strength with the introduction of CSA cement and the same increase of
values in the compressive strength results with the CSA cement introduction was observed too. Thus,
it is concluded that for small amounts of binder, about 12,5 to 14 %, the CSA cement does not benefit
the rendering mortars durability.
3.2 Basecoat mortars for ETICS
The basecoat mortars results are presented in the table 6 where the average values for each test are
showed.
The basecoat mortars exhibited more clear results regarding the introduction of CSA cement. In the
fresh state was verified the same results as the rendering mortars, a bigger plastic effect introduced by
CSA cement, decreasing the setting times, 300 to 650 minutes, and flow values, until 15 %.
As for the rendering mortars, the bulk density, dynamic elastic modulus, compressive strength and
open porosity presented demonstrate the same trend. Analyzing the bulk density it is observed a slight
decrease of the values with the CSA cement introduction, which increase with the increase of this
binder quantity. The CSA cement reference mortar exhibits a bulk density increase of a little more than
20 % relatively to the Portland cement reference mortar. Concerning the compressive strength, the
increase is higher, having again a first decrease of the strength with the CSA cement introduction,
which rapidly increase with the quantity of the CSA cement introduced. The both mortars with more
CSA cement quantity clearly demonstrate values over the two first ones, and the CSA cement
reference mortar exhibit the double of the compressive strength of the Portland cement reference
mortar. In the dynamic elastic modulus is observed again a values decrease with the entry of CSA
cement, highlighting the value of the CSA cement reference mortar, which is 30 % higher than the
mortar only constituted by Portland cement. In the open porosity, despite the mortar only constituted
by CSA cement which exhibit a low result due the accelerator use, the BOP:+CSA mortar demonstrated a
10 % value higher than the Portland cement reference mortar. These results allow to conclude the
same as the rendering mortars, in a clearly way, the values increase when the quantities of CSA
cement are higher and decrease when are lower.
Like the rendering mortars the tensile strength decrease for the half when CSA cement is introduced,
which can support the idea of a weak internal cohesion of this binder.
Regarding to the dimensional variations, the mortars demonstrate great results. Thus, was verified a
linear relation between the decrease of shrinkage and the increase of CSA cement quantity. The both
mortars with more CSA cement show half or less of the shrinkage values relatively the Portland
cement reference mortar. As opposed of the rendering mortars there was no instability in the results,
which may indicate that mortars with low binder quantities are more propitious to instability.
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Table 6 – Basecoat mortars results
Mortar BOP B+OP:CSA BOP:+CSA BCSA
Test
Fresh State
Consistence (flow value) (mm) 152 150 130 125
Bulk density (kg/m3) 1452,52 1477,7 1344,48 1431,18
Setting time with regulators (min) 720/750 105/180 60/180 20/75
Setting time without regulators (min) 720/750 5/30 60/180 345/450
Hardened State
Bulk density (kg/m3) 1440 1397,23 1444,49 1786,43
Tensile strength (MPa) 3,42 1,66 1,59 1,79
Tensile strength after water immersion curing conditions (MPa)
2,97 1,71 1,9 2,1
Compressive strength (MPa) 6,77 6,1 9,1 13,83
Compressive strength after water immersion curing conditions (MPa)
5,55 6,13 5,51 6,38
Dimensional variation (shrinkage) (mm/m) 2 1,63 1,04 0,6
Dimensional variation (shrinkage) after water immersion curing conditions (mm/m)
0,29 1,09 0,49 -1,45
Mass variation (g/kg) -94,06 -98,08 -82,47 -67,91
Mass variation after water immersion curing conditions (g/kg)
36,7 32,66 37,92 55,52
Dynamic elastic modulus (MPa) 9862,9 6125,07 7957,78 12747,46
Water absorption coefficient due to capillary (kg/(m2.min0,5)
0,04 0,05 0,03 0,05
Water absorption at low pressure (ml) 1,3 0,2 0,2 0,15
Water vapor diffusion coefficient 5,73 6,29 7,4 5,29
Open porosity (%) 40,4 38,7 44,35 29,12
Adhesive strength in concrete substrate after water immersion curing conditions (MPa)
0,55 (50% AFT/ 50%
CFA)
0,47 (85% AFT/ 15%
CFA)
0,60 (50% AFT/ 50% CFA)
0,19 (95%
AFT/ 5% CFA)
Adhesive strength in concrete substrate after heat curing conditions (MPa)
0,07 (95% AFT/ 5%
CFA)
0,25 (95% AFT/ 5%
CFA)
0,51 (40% AFT/ 60% CFA)
- (unglued during the
curing conditions
)
Adhesive strength in EPS substrate after water immersion curing conditions (MPa)
0,08 (AFS)
0,11 (AFS)
0,12 (80% CFS/ 20% AFS)
0,02 (79%
AFT/ 21% AFS)
Adhesive strength in EPS substrate after heat curing conditions (MPa)
0,06 (31% AFT/ 65% AFS/ 4%
CFS)
0,06 (20% AFT/ 80%
AFS)
0,02 (95%
AFT/ 5% AFS)
0,04 (34%
AFT/ 62% AFS/ 4%
CFS)
Durability (after freeze-thaw curing conditions)
Dimensional variation (shrinkage) (mm/m) 3,47 1,98 0,26 -1,71
Mass variation (mm/m) -6,82 39,2 9,12 -10,34
Tensile strength (MPa) 3,45 1,92 1,95 1,99
Compressive strength (MPa) 6,42 6,35 4,9 6,61
AF-T: Adhesive rupture between the bonding product and the ceramic tile; AF-S: Adhesive rupture between the bonding product
and the substrate; CF-A: Cohesive rupture in the bonding product; CF-S: Cohesive rupture in the substrate.
13
The water absorption coefficient due to capillary and water absorption at low pressure results do not
demonstrate consistent like was observed in the rendering mortars. This situation due to the water
absorption coefficient due to capillary, where was verified a values variation difficult to relate with the
quantities of the two binders. With respect to the water absorption at low pressure, the results were
like the rendering mortars, having about 85 % decreases in the values of the Portland cement
reference mortar for the others. Showing a trend like the rendering mortars, the water vapor
permeability results demonstrate an increase in the resistant to vapor diffusion in the mortars
constituted for the both binders, which increase with the quantity of CSA cement.
In the after water immersion curing tests, the tensile and compressive strengths demonstrated two
different situations. The tensile strength exhibited the same trend that after normal curing conditions,
however the compressive strength after water immersion curing conditions demonstrated a different
result that after normal curing conditions, where was verified a constancy in results between the four
mortars instead the increase of the strengths with the CSA cement increase like after normal curing
conditions. Faced with these results, concludes that the CSA cement introduction for the compressive
strength after water immersion curing conditions has the same effect as Portland cement, not
providing any change in the results. Regarding the shrinkage results, these were all within the normal
limits except the BCSA (mortar with just CSA cement) mortar, which has a 1,25 mm/m expansion.
The specimen’s state after the durability test confirms an acceptable state, which is justified by the
higher binder quantity introduced. The shrinkage and tensile strength results confirm the same
observed trends for the normal and immersion curing conditions, concluding about the low influence of
the durability curing conditions effects in the CSA cement. Also in the compressive strength results
were verified the same trend that the immersion curing conditions, leading to the same conclusion.
Lastly, the adhesive strength in concrete and EPS substrate results demonstrated, in general, a linear
relation between the increase of adhesive strength and the increase of CSA cement introduction, with
the except of the EPS substrate after heat curing conditions results, where was verified a values
decrease. However, and being a single case, it is proposed the repetition of this test. Faced with these
results and the adhesive strength in brick substrate results of rendering mortars it is verified a
contradiction, for the latter case was observed a values decrease with the CSA cement introduction
and a respective bad adhesion to the substrate. Thus, it is plausible to suspect that the CSA cement
provide a weak adhesion to the substrate when it is introduced in mortars with a low binder quantity,
as the rendering mortars.
3.3 Results comparison
The following graphs present some analyzed characteristics with the results of both products. It is
made an analysis for both studied products based on the results and the approximate trend lines, in
order to reach the influence of Portland cement, CSA cement and other variables.
14
3.3.1 Setting initial and final time without regulators
The figures 1 and 2 presented the setting times for the studied mortars, with the difference that will be
the times without setting time regulators in the mortars where were used the regulators.
Figure 1 – Setting initial times of rendering and basecoat mortars without regulators and the respective trend curves
Figure 2 - Setting final times of rendering and basecoat mortars without regulators and the respective trend curves
Observing the figures 1 and 2, it is verified the similarly of results between the two products, which
reinforce the withdrawn conclusions. All the results are close to a 2º degree polynomial with R2 values
close to the unit. Thus, it is concluded that the setting times mainly depend on the relation between the
two binders, however, it is still possible to observe the decreasing of the setting time with de entry of
CSA cement.
3.3.2 Bulk density in hardened state
The bulk density in hardened state results for the two products and the respective approximate trend
lines can be consulted in the figure 3.
As concluded before, the introduction of CSA cement may introduce an increase in the bulk density in
hardened state. The rendering mortars results approximate to a 2º degree polynomial with a low R2
value, suggesting an additional influence besides the quantities of the two binders. The rendering
mortars due to have a lower quantity of binder than the basecoat mortars may exhibit more sensitive
R² = ,0,962
R² = ,0,955
-100
0
100
200
300
400
500
600
700
800
OP +OP:CSA OP:+CSA CSA
Tim
e [m
in]
Setting initial time without regulators
reboco camada de base Polinomial (reboco) Polinomial (camada de base)
R² = ,0,912
R² = ,0,907
0
100
200
300
400
500
600
700
800
OP +OP:CSA OP:+CSA CSA
Tim
e [m
in]
Setting final time without regulators
reboco camada de base Polinomial (reboco) Polinomial (camada de base)
15
behaviors in certain properties. Concerning to the basecoat results confirm the dependence of the
relationship between the two binders for the bulk density results, not allowing observing a slight values
increase when the CSA cement is in higher quantities.
Figure 3 – Bulk density in hardened state of rendering and basecoat mortars and the respective trend curves
3.3.3 Compressive strength after normal curing conditions
The results comparison of compressive strength, after normal curing conditions, of the two products
and the respective approximate trend lines can be consulted in the figure 4.
Figure 4 – Compressive strength of rendering and basecoat mortars and the respective trend curves
Has shown on the results observation, both products have the same trend of dependence of the two
binders, although the rendering mortars R2 value is not as certain as the basecoat mortars value, with
a R2 of 0,995. In fact, the basecoat mortars have a reasonable R2 value, 0,797, for a linear trend line,
demonstrating a compressive strength increase with the increase of CSA cement introduced, although
this property also depends on the Portland cement quantity.
3.3.4 Tensile strength after normal curing conditions
The results comparison of tensile strength, after normal curing conditions, of the two products and the
respective approximate trend lines can be consulted in the figure 5.
R² = ,0,979
R² = ,0,588
1300
1400
1500
1600
1700
1800
1900
OP +OP:CSA OP:+CSA CSA
Bulk
density [kg/m
3]
Bulk density in hardened state
camada de base reboco Polinomial (camada de base) Polinomial (reboco)
R² = ,0,995
R² = ,0,797
R² = ,0,835
0
5
10
15
OP +OP:CSA OP:+CSA CSA
Com
pre
ssiv
e s
trength
[M
pa]
Compressive strength
camada de base reboco Polinomial (camada de base)
16
For both products was observed the decrease of tensile strength with the introduction of CSA cement.
Also, stands out the fact of the rendering mortars trend curve be a 2º degree polynomial with R2 value
of 0,766, suggesting additional variables that condition the property in study.
Figure 5 – Tensile bending strength of rendering and basecoat mortars and the respective trend curves
The decreasing of the tensile bending strength with the CSA cement entry as opposed to the increase
of the bulk density, dynamic elastic modulus and compressive strength may be related with the
internal cohesion. This issue is reinforced when is observed the adhesive strength in brick substrate
results, where was verified clearly the same, verifying a lowest cohesion too. However, in the adhesive
strength in concrete and EPS substrate analysis was observed an increase of the strengths with the
increase of the CSA cement quantity introduced. This increase in the most of the tests was
proportional to the increase of CSA cement quantity. These results are contradictory with the
rendering mortars results; thus, the CSA cement introduction in rendering mortars is clearly prejudicial
for the internal cohesion and for the adhesion to the substrate, and in the basecoat mortars is
prejudicial to the internal cohesion but not for the adhesion to the substrate, although some results in
EPS substrate demonstrate this problem.
3.3.5 Shrinkage after normal curing conditions
The results comparison of shrinkage, after normal curing conditions, of the two products and the
respective approximate trend lines can be consulted in the figure 6.
Figure 6 – Shrinkage of rendering and basecoat mortars and the respective trend curves
R² = ,0,956
R² = ,0,766
0
0,5
1
1,5
2
2,5
3
3,5
4
OP +OP:CSA OP:+CSA CSA
Te
nsile
bendin
g s
trength
[M
pa]
Tensile bending strength
camada de base reboco Polinomial (camada de base) Polinomial (reboco)
R² = ,0,993
R² = ,0,971
0
0,5
1
1,5
2
2,5
OP +OP:CSA OP:+CSA CSA
Shrin
kage [m
m/m
]
Shrinkage
camada de base reboco Linear (camada de base) Polinomial (reboco)
17
In this figure, it is noted the linear relation for the basecoat mortars, with a R2 value of 0,933. This
value demonstrates the direct relation between the shrinkage decrease and the CSA cement quantity
introduced. The rendering mortars shows the same shrinkage decrease with da CSA cement
introduction, excepting the CSA cement reference mortar, which exhibit a very high results, and
although repeating the tests the results revealed the same instability. Thereby, it is concluded that
may have some instability in the dimensional variation when the mortars are made only by CSA
cement.
3.3.6 Water absorption at low pressure after 180 minutes
The results comparison of water absorption coefficient due to capillary of the two products and the
respective approximate trend lines can be consulted in the figure 7.
Figure 7 – Water absorption at low pressure of rendering and basecoat mortars and the respective trend curves
Looking at the results of figure 7, it can be observed the consistency between the products, concluding
that the water absorption coefficient due to capillary decrease with the CSA cement introduction. In
addition both results are approximate to a 2º degree polynomial, resulting once again in the
dependence of the two binders in cause, suggesting that this property is closely related with the
mortars compactness.
R² = ,0,929
R² = ,0,905
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
1,4
OP +OP:CSA OP:+CSA CSAWate
r absorp
tio
n a
t lo
w p
resure
[m
l]
Water absorption at low pressure after 180 minutes
camada de base reboco Polinomial (camada de base) Polinomial (reboco)
18
4 Conclusions
In the analyzed results for the two products, it is possible to find common points. Therefore, the
common conclusions for two products, related to the CSA cement introduction are the following:
Setting time reduction, 90 to 300 minutes for the rendering mortars and 300 to 650 minutes to
the basecoat mortars;
Plastic effect in the mortars, decreasing the flow, until 15 %;
Increase of bulk density in the hardened state (2 % for the rendering’s and 20 % for the
basecoat’s), compressive strength (12 % for the rendering’s and 100 % for the basecoat’s)
and dynamic elastic modulus (10 % for the rendering’s and 30 % for the basecoat’s), but only
when in high quantities of CSA cement;
Tensile strength reduction, 20 to 45 % for the rendering mortars and about 50 % for the
basecoat mortars;
Shrinkage reduction in the presence of this binder, 15 to 25 % for the rendering mortars and
20 to 70 % for the basecoat mortars;
Reduction of water absorption at low pressure, in about 85 %.
Regarding to the durability, the rendering mortars results demonstrate a deteriorated state, concluding
that for small quantities of binder, 12,5 to 14 %, the CSA cement does not benefits the rendering
mortars durability. In the basecoat mortars, the specimens showed an acceptable state and the tests
results indicated the same trend observed for the normal and immersion curing conditions , concluding
about the small influence of the durability curing conditions effects in the CSA cement.
In the water immersion results, and for the rendering mortars, the results showed the same trend that
after normal curing conditions, except in the shrinkage test, that was one mortar, the mortar with both
binders with the CSA cement with more amount (ROP:+CSA), who expanded. In the basecoat mortars
the tensile strength showed the same trend that the normal curing conditions, but in the compressive
strength was a results constancy between the four mortars and not the increasing of the strength with
the increase of CSA cement amount as was verified in the normal curing conditions. The shrinkage
tests results were all within the normal limits, except for the CSA cement reference mortar (BCSA)
which had a 1,25 mm/m expansion.
Essentially, the highest water consumption of CSA cement provides that there is less free water in the
mortars, having less water to evaporate, and consequently less free spaces in the mortar. Thus, the
CSA cement introduction leads to more compact mortars with a lowest shrinkage and mass loss. The
presented facts explain the increasing trend for the bulk density in hardened state, dynamic elastic
modulus, compressive strength and explain the water absorption due to capillary and water absorption
at low pressure decreasing, with the increase of CSA cement, but often depending on the relation with
the Portland cement. Thus, stands out that the shrinkage after water immersion curing conditions can
cause an expansion effect in the mortars composed mostly or totally by CSA cement.
19
Despite these results being common in the both studied products, clearly reveals the fact that the
basecoat results are more expressive, as it was possible to check in the R2 values. Concluding, from
the rendering mortars analysis, which the CSA cement introduction in these mortars, with a lower
binder percentage, may lead to some instability in certain properties. In the basecoat mortars for
ETICS, where aims a thinner and more resistance layers, the CSA cement introduction clearly
demonstrated an improvement in certain properties. Thus, was demonstrated that the CSA cement
introduction in higher percentages of binder is more stable.
Analysing the comparison with the EN 998-1 (CEN, 2010a), LNEC (2005), ETAG 004 (EOTA, 2000),
MERUC classification requirements and finally the mortars average values of the market (Flores-
Colen, 2009), it is verified that in general all the mortars presented a reasonable performance and are
within the requirements, except for the water vapor permeability. Thus, the mortars with CSA cement
present a reasonable performance, meaning that de replacement of Portland cement for CSA cement
can be viable, obtaining mortars with a similar performance with an improvement in sustainability.
Faced with these facts, it is concluded that the objectives were fulfil, highlighting the fact that basecoat
mortars with more CSA cement quantity clearly demonstrated better results in the setting time and
shrinkage, and presented similar or better performances in the other properties relative to the mortars
with more Portland cement. Thus, it was achieved better performances in certain properties, or at least
kept them in an appropriate level, and achieved a clearly improvement in the setting time and
shrinkage, allowing to reach an advantage product for a rapid application.
Nevertheless, it is proposed to continue the dimensional variations and mass studies, in order to
understand some detected uncertainties, the internal cohesion analysis of CSA cement mortars and
the evaluation of the CSA and Portland cements interconnection.
20
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21
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