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Article

The Effect of Superabsorbent Polymers on Mechanical Characteristics and Cracking Susceptibility of Alkali-Activated Mortars Containing Ground Granulated Blast-Furnace Slag and Copper Slag

by
Stewart MacLennan
1,
Fernando C. R. Almeida
2 and
Agnieszka J. Klemm
1,*
1
School of Computing, Engineering and Built Environment, Glasgow Caledonian University, 70 Cowcaddens Road, Glasgow G4 0BA, UK
2
Department of Materials Engineering and Construction, Federal University of Minas Gerais, 6627 Av. Presidente Antônio Carlos, Belo Horizonte 31270-901, Brazil
*
Author to whom correspondence should be addressed.
CivilEng 2022, 3(4), 1077-1090; https://doi.org/10.3390/civileng3040061
Submission received: 11 October 2022 / Revised: 1 December 2022 / Accepted: 2 December 2022 / Published: 9 December 2022
(This article belongs to the Special Issue Concrete in Structural Engineering for Sustainability)
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Abstract

:
In an attempt to increase sustainability of construction materials, both ground granulated blast-furnace slag (GGBS) and, less popular, copper slag (CS) can be used in alkali-activated composites. However, such composites are often more susceptible to cracking, triggered by the self-desiccation processes. The addition of superabsorbent polymers (SAP) may enable internal curing of concrete and prevent excessive cracking. Thus, this paper aims to evaluate the effectiveness of SAP as an internal curing agent for alkali-activated slag mortars containing GGBS and CS. The samples were activated by sodium silicate using 6.5% Na2O by mass of precursor. The evaluation was based on the analysis of mechanical properties, autogenous shrinkage, and water absorption capacity of two types of SAPs. Depending on the type of polymer, a higher alkali concentration in SAP solutions speeds up early age reactions up to 7 days. After this period, SAP collapses and reactions follow at the same pace as the reference sample. In the presence of CS, SAP with higher absorption and smaller particles well-distributed in the mix leads to a higher extension of reactions, observed in higher values of autogenous shrinkage (AS). This results in increased compressive strength of GGBS-CS mortars, achieving values 8.8% greater than the reference sample (without SAP) at 6 months. Although its leads to higher cracking susceptibility, SAP can improve mechanical properties and promote new applications for sustainable material containing copper slag.

1. Introduction

It is a well-known fact that the production of Portland cement (PC) is one of the major contributors to greenhouse gas emissions. Production of cement-based materials alone is responsible for more than a third of raw construction materials extracted from nature and 5–10% of anthropogenic CO2 [1,2]. It is now a common practice to incorporate supplementary cementitious materials (SCM) based on industrial by-products [3,4,5]. This sustainable approach results in environmental and economic benefits by reducing energy and consumption of non-renewable resources. It also avoids contamination of the natural environment, depletion of natural resources and reduced capacity of final waste disposal arrangements [6,7]. Many alternative materials have been successfully used as a PC replacement, such as fly ash [8], blast-furnace slag [9], silica fume [10], ceramic waste powder [7], coal bottom ash and waste glass sludge [11], tires waste [12], rice husk ash [13], sugarcane bagasse ash sand [14], iron ore tailings [15], water treatment plant sludge [16], among others. This paper is focused on ground granulated blast-furnace slag (GGBS) and less popular, copper slag (CS) [5,17,18].
Ground granulated blast-furnace slag (GGBS) is often used as an effective cement replacement, which can benefit the final hardened product with regards to durability requirements, mechanical properties, and economic reasons. GGBS is a latent hydraulic binder, which reacts very slowly without a suitable activator. The reaction between slag and water produces a protective film, which is deficient in calcium, stifling progress of the hydration process [19]. To minimize this effect and activate the reaction, an alkali environment is highly recommended. In PC-GGBS blended binders, cement portion facilitates the production of alkali calcium hydroxide and permits hydration of slag. Moreover, high glass content of GGBS makes it better suited for cement replacement due to its higher reactivity [20,21]. Once a critical pH is achieved, the glassy structure of slag is disrupted, and the latent hydraulic reaction with water is initiated. The main product of this reaction is calcium silicate hydrate (C-S-H) gel, which is the same product of PC hydration. However, the reaction does not produce calcium hydroxide [22].
Copper slag (CS) is a waste product formed during smelting and refining of copper. Similar to GGBS, CS floats on top of pure metal after the mix of ore concentrate and silica has been heated in a flash furnace. The production of copper metal produces CS in quantities reaching 2.2 times the mass of copper production (i.e., 2200 kg of CS for 1000 kg of copper) [23]. Copper slag has been traditionally used as fine aggregate, but when used in conjunction with GGBS as precursors, it can improve cementitious properties. Both slags possess some hydraulic properties but require alkali activation to achieve the pace of strength development by PC, particularly during the first 14 days [24,25].
Alkali activation involves dissolution of an aluminosilicate precursor in an alkali solution (usually, based on sodium silicate), forming a semi-crystalline silico aluminate polymeric structure. The role of sodium silicate solution is to release Si and Al from glass-rich slags [24]. Song et al. [19] reported 11.5 alkalinity of the glassy structure to be activated, although this depends on the reactivity of the slag, activator, and temperature. When an adequate quantity of Si and Al is available, these elements can then polymerize with SiO2, which is available within sodium silicate and precursors. The main reaction products formed as a result of GGBS and CS reaction are calcium silicate hydrate (C-S-H) and/or calcium aluminate silicate hydrate (C-A-S-H) and, occasionally, sodium aluminosilicate hydrate (N-A-S-H) [26]. However, the reaction products occupy less space than the reactants. This in turn makes the composite more susceptible to cracking, triggered by both self-desiccation processes and subsequent autogenous shrinkage (AS).
The addition of superabsorbent polymers (SAP) has proven to be effective in reducing the cracking formation by enabling internal curing of PC-based concrete [27,28,29,30,31]. SAP provides additional water for a longer period of cement hydration. This supplemental water at later stages results in densification of matrix and shrinkage reduction in cement paste. Although application of SAP in alkali-activated materials has been previously studied, the publications were focused on composites containing only GGBS as a precursor [32,33,34,35]. Therefore, the contribution of this paper to the current body of knowledge is based on the application of SAP in alkali-activated materials incorporating not only GGBS but also CS.
The aim of this paper is to evaluate the effectiveness of SAP as an internal curing agent in sodium silicate-activated mortars with GGBS and CS as precursors. The assessment was based on the analysis of mechanical properties, autogenous shrinkage, and water absorption capacity of two types of SAPs.

2. Materials and Methods

Mortars have been designed using different content of GGBS and CS as precursors. GGBS was provided by LKAB Minerals (Derby, UK) and CS by Scangrit (Immingham, UK). Table 1 shows the chemical compositions of GGBS and CS used in the experimental study.
The particle size distribution of GGBS and CS was obtained by laser diffraction method (Figure 1). Although both precursors have a similar shape of particle distribution, CS has a wider distribution of coarser particle sizes.
Sodium silicate (silicate modulus Ms = 2.05, and density = 1.686 g/cm3) was used to activate the precursors. For alkali solution, 6.5% Na2O by mass of slag was calculated for each 50 mL of fluid volume. The content of Na2O in the sodium silicate solution was 17.8%.
Mixes were activated by sodium silicate solution, in the ratio of fluid volume/precursor (F/P) of 0.55. The notation used to signify this is fluid volume/precursor (F/P) where the volume of fluid remains the same and the density of activator was used to calculate the required volume.
For mortar production, fine sand was used as an aggregate in the ratio of 1:2 (precursor: sand). At least 90% of particles sizes were below 0.43 mm, with a bulk density of 1.40 g/cm3.
Two types of superabsorbent polymers (SAP), with different water absorption capacities, have been used in the content of 0.25% by mass of precursor. They were both based on the same polymer (modified polyacrylamide) but had different particle sizes: SAP C (30–140 μm) and SAP E (20–130 μm), as shown in Figure 1. SAP E has a larger proportion of particles in the 0–60 µm range; it is also better graded in comparison to SAP C.
Table 2 shows the sample mix compositions used in the experimental study.
The water absorption of SAP was measured by the tea-bag test [36,37]. The readings were taken in triplicate at 1, 5, 10, 30, 60, and 180 min. Alkali solutions were prepared using the following combinations of precursors: 100:0, 75:25, and 50:50 of GGBS and CS, respectively. Sodium silicate Ms = 2.05 @ 6.5% Na2O by mass of precursor was maintained and compared. At the same time, pH of the solutions was measured by the Fisher Scientific (Waltham, MA, USA) accumet AP110 pH-meter.
Workability of fresh mortars was evaluated using the flow table according to BS EN 1015-3 [38] and setting times measurements were carried out according to BS EN 196-3 [39]. Autogenous shrinkage (AS) measurements were taken regularly in triplicate over a 90-day period using the corrugated tubes method, according to ASTM C1968-09 [40,41]. Compressive strengths readings were taken from six samples at 30, 90, and 180 days, according to BS EN 1015-11 [42].

3. Results and Discussion

Figure 2 shows water absorption capacities (WAC) of SAPs in different solutions during a period of 3 h.
The lowest WAC in the first 30 min was attained for 100GC solution, followed by 50GC. This can be attributed to a high number of calcium ions within GGBS, which inhibit SAP absorption capacity [43]. This tendency is more pronounced with SAP C. The highest WAC occurs initially in 75GE solution. In the later stages (after approx. 45 min), the highest WAC was achieved in 100GE solutions.
Figure 3 shows water absorption capacities (WAC) of SAPs in different solutions during a period of 24 h.
The greatest SAP absorptions were exhibited in 100GE and 75GE solutions. Considering that both SAPs have identical chemical composition, the difference in WAC can be attributed mainly to their particle sizes, i.e., SAP E (finer particles) has a faster and greater water absorption capacity.
Table 3 shows results of pH measurements of alkali solutions with and without SAP (reference). The addition of SAP promotes higher pH after 1 day. This is because there is an enrichment of the alkali solution when used in conjunction with SAP. As SAP absorbs water, pH values of GGBS-CS-activated solutions are slightly increased due to higher concentration of alkali ions. On the contrary, reference mixes showed a dilution effect, i.e., the same amount of alkaline ions diluted in a larger portion of free-water available in the solution. Moreover, the reference solutions are more sensitive to reduction in pH due to the carbonation effect [44,45]. Overall, SAP E solutions had a slightly higher pH reading, which can contribute to the alkali activation principle.
Workability of mortars was measured by flow table tests, and the results are shown in Figure 4.
CS addition in each mix notably reduced the flow values. Table 4 shows workability reduction (in percentages) for different mortars with increasing replacement level of CS using 100G as the reference. The replacement of GGBS with 25% of CS results in an approximately 5.4% decrease in workability. The addition of a further 25% results in a 23.2% reduction in workability.
The relationship between copper slag replacement and loss of workability is not in a proportion of the replacement level. This is mostly due to high water demand of CS, given by irregular shapes and higher specific surface area of particles. High hardness of copper slag and the grinding process led to sharply crushed particles, which are interlocking within the fresh mix.
Table 5 is based on the same principle as above but focusses on the workability reduction, resulting from the addition of SAP. The change is calculated using the corresponding reference sample (without SAP) as a comparison, i.e., 100GC and 100GE is compared with 100G.
As expected, the addition of SAP in both cases reduced workability of each set due to a volume of fluid, which is retained in SAP particles (hydrogel). This extra water is stored in small reservoirs distributed throughout the matrix and, therefore, reducing extra water required between solids to attain greater flow. SAP E inclusion in 75% GGBS samples results in the greatest change in workability (11.3%) caused by the highest absorption level. Reduction in flow in 100GE samples reaches 9.6% and in 50GE samples only 5.4%. The incorporation of SAP C in the 100G mixes results in an 8.9% reduction in workability and 6.9% reduction in the 75G samples. For 50G samples, the reduction is only 3.1%. This indicates that the addition of SAP has a smaller effect than the level of CS replacement.
Figure 5 shows initial and final setting times results by Vicat test. The addition of CS within the mix significantly increases the setting times.
The longer setting time is due to a low early-age activity of copper slag. In this case, CS is acting as an aggregate with little to no reactions taking place in the early ages. Copper slag has higher water demand, leading to a stiffer mix in the fresh state. In the first hours, GGBS is reacting, providing stiffness, and shortening setting times. For samples with low content of GGBS, the reactions are notably slower. This can also be attributed to the higher alkali content of GGBS (especially by CaO) compared to CS (Table 1), which contributes to faster reactions of alkali-activated system.
When SAP is added, no significant changes are observed due to the high scatter of results. However, in absolute values, it seems that SAP slightly reduces initial setting time. This effect is not as evident in the final setting times, where higher water demand of CS mixes is apparent. The final setting time for 100G samples is extended by SAP E. The 75G mortars show a small reduction when SAP C is added but not for SAP E, where values are approximately the same. The addition of both SAP C and E prolongs the final setting time of samples containing 50% of copper slag.
Figure 6 shows autogenous shrinkage (AS) results of reference mortars (without SAP). A progressive increase in copper slag in composites results in reduction in AS. This is due to the higher reactivity of GGBS over CS, where more reactions occur in the reactive GGBS precursor. The 100G and 75G samples experience very rapid autogenous shrinkage, whereas the 50G sample has a low shrinkage and slower onset.
Again, low reactivity of CS (even in an alkali-activated environment) makes this precursor acting as an aggregate, thus reducing AS. By contrast, a high amount of GGBS increases the degree of reaction and consequently AS, due to its higher glass content and higher CaO content.
Figure 7 shows autogenous shrinkage of GGBS mortars with and without SAPs. During the first 3 days, AS values are similar for all samples. However, after this period, the positive effect of SAP C is much more pronounced, and the reduction in AS is well evidenced.
SAP E results in higher shrinkage. Its finer particles create well distributed water reservoirs in mixes, increasing the degree of reaction from the precursors and affecting volume change. SAP E appears to increase AS in the first days.
Figure 8 shows AS results for samples containing 75% GGBS with and without polymers, (75G, 75GC, and 75GE). The highest AS value resulted from the incorporation of SAP E. Again, this can be attributed to temporarily increased alkali concentration by SAP.
A similar pattern was found for the 75% and 100% GGBS samples. It appears that SAP C reduces AS whereas SAP E increases AS. However, the slope of curves for samples with SAP C and SAP E is almost identical in the first three days. This slope is also higher when compared to that formed by the reference sample (without SAP). This indicates a higher kinetics of reaction given by SAP.
Figure 9 shows results of autogenous shrinkage for samples with 50% GGBS.
As it can be seen, the 50GE sample exhibited the greatest AS. The finer SAP E better distributed water reservoirs than SAP C. This results in less space between SAP particles within the matrix and reduction in osmotic pressure required to continue the reaction. SAP increases alkalinity of systems and allows for enhanced hydration reactions. It appears that mortars benefit from finer particles of SAP. For samples without SAP, there is a dilution effect on the activator, which reduces the completeness of alkaline reaction. This suggests that the reaction products and internal humidity govern the future reactions. This effect is dependent on the CS substitution level and type of SAP used. The 50GE sample has undergone more polymerization than the 50G and 50GC groups.
Thus, the results show that the addition of SAP has a twofold effect on GGBS-CS alkali-activated materials, changing the rate and degree of reactions:
  • Rate of reaction: SAP increases kinetics of alkali-activated GGBS-CS reactions. The water retention by SAP results in a higher alkali concentration available in the solution to activate the precursors, speeding up reactions. The capacity to maintain this effect depends on the type of polymer. SAP C (with lower WAC) is able to accelerate reactions up to approximately 3 days, while SAP E (higher WAC) can contribute up to 7 days. After this period of time, SAP collapses and reactions seem to follow at the same pace as the reference sample (without SAP).
  • Degree of reaction: The effect of SAP depends on the type of precursor, especially in the capacity to form silicates in the presence of CS. In this case, SAP E, with higher absorption and smaller, well-distributed particles in the mix, leads to higher extension of reaction. In turn, the bigger particles and lower water absorption of SAP C can leave behind larger pores (after SAP collapsing), allowing more room for any volume change and reduction in AS of mortars. For samples with low or no CS content, the degree of reaction is less affected because GGBS (with higher reactivity) is rapidly activated by the alkali solution. At 90 days, the level of AS (which indicates the extension of this effect) is comparable to all GGBS samples (with or without SAP).
This outcome is in line with compressive strength results shown in Figure 10. All samples were tested at 1, 3, and 6 months.
Overall, the addition of CS, due to its lower reactivity, reduces compressive strength in all cases. SAP E seems to be more beneficial than SAP C, especially in higher CS levels. SAP E help to maintain the alkali loading and provide transport to ions in order to continue the reaction, as observed in Figure 9. SAP E particles are closely spaced, and the exchange of water from SAP to the reaction front is promoted with less osmotic pressure than that of SAP C. SAP E is able to increase 7.3% and 8.8% of compressive strength at 6 months, respectively, for mortars with 25% and 50% CS (Table 6).
By contrast, SAP C is not as effective due to significant spacing between SAP hydrogels. SAP C has water for longer, but the products of reaction prevent transport of ions to promote polymerization. Moreover, low WAC of SAP C leaves behind more pores in collapsed state, which are not able to be refilled by later hydration products. At 6 months, the reduction in compressive strength by SAP C was in the order of 7.1%, 6.7%, and 10.6%, respectively, for samples with 100%, 75%, and 50% GGBS (Table 6).
Thus, there is a balance between quantity of CS replacement and efficiency of SAP (given by the water retention capacity and ability to form smaller pores in the collapsed state). In general, CS-GGBS mixes are enhanced by SAP E. The 50GE samples have the greatest AS, triggered by its higher reaction degree, which correlates with the higher compressive strength results. The same concept is applied for the 75GE sample, which showed better results in comparison to the respective reference sample and sample with SAP C. The 50G sample had a very low shrinkage value due to low CS reactivity, which is reflected in low compressive strength results. The smaller particle sizes of SAPs are contributing to a greater reservoir of water and better distribution in the matrix. Thus, SAP E seems to be better suited for alkali-activated mortars. This allows for a higher initial alkali concentration, which maintains pH at higher levels. The faster and extended reactions lead to a higher autogenous shrinkage and an increased compressive strength.

4. Conclusions

From the experimental data, the following conclusions can be drawn:
(a)
Copper slag (CS) has lower reactivity than ground granulated blast-furnace slag (GGBS), even in a sodium silicate-activated system. CS acts as an aggregate when no water control takes place. This results in prolonged setting time, lower autogenous shrinkage, and lower compressive strength;
(b)
Water absorption capacity (WAC) of superabsorbent polymers (SAP) leads to increased pH values of systems due to lower dilution of alkali ions in aqueous solution. SAP with finer particles absorbs faster and more water from alkali-activated GGBS-CS solutions. However, this reduces workability of mortars up to approximately 10%, for mixes with the same ratio of fluid volume/precursor;
(c)
SAP increases the rate of activated GGBS-CS reactions observed in higher slopes of autogenous shrinkage curves. Depending on the type of polymer, a higher alkali concentration of SAP solutions speeds up early age reactions up to 7 days. After this period, SAP collapses, and the pace of reaction follows as for the reference sample;
(d)
SAP may also increase the degree of reactions, depending on the type of polymer and type of precursor. In the presence of CS, SAP, with higher absorption and smaller particles well-distributed in the mix, leads to a higher extension of reaction. For samples with high GGBS content (above 75%), the degree of reaction is less affected by SAP because of higher slag reactivity, which is rapidly activated by the alkali solution. At 90 days, the level of autogenous shrinkage is comparable to all GGBS mortars (with or without SAP);
(e)
The effect of faster and extended reaction of activated GGBS-CS mortars by SAP reflects in higher compressive strength. SAP with lower WAC and larger particles may lead to decreased autogenous shrinkage by providing more room for volume changes after its collapsing. However, it may lead to the reduction in compressive strength by 10% at 6 months, especially at high CS contents. On the contrary, finer SAP with higher WAC has higher ability to increase compressive strength of GGBS-CS mortars, achieving values 9% greater than the reference sample at 6 months.
Therefore, finer particles of SAP, with higher absorption capacity, are more suited for enhancement of polymerization reaction in alkali-activated GGBS-CS mortars. Although this leads to higher cracking susceptibility, mechanical properties may be improved. This in turn promotes a new application for a sustainable material using copper slag. However, in terms of research limitations, the major issue is related to the origin of precursors and manufacturing processes involved. Therefore, future research should be focused on assessment of the robustness of SAP in matrices derived from different mineral sources across the world.

Author Contributions

Conceptualization: S.M. and A.J.K.; Methodology: S.M. and A.J.K.; Formal analysis: S.M., F.C.R.A. and A.J.K.; Investigation: S.M.; Writing—original draft preparation: S.M., F.C.R.A. and A.J.K.; Writing—review and editing, S.M., F.C.R.A. and A.J.K.; Supervision: A.J.K.; Project administration: A.J.K. All authors have read and agreed to the published version of the manuscript.

Funding

F.C.R. Almeida was supported by FAPEMIG (grant number APQ-00062-22).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data sharing is not applicable for this article.

Acknowledgments

The authors acknowledge LKAB Minerals for GGBS supply, Scangrit for CS supply, and BASF Construction Chemicals GmbH for SAPs supply. F.C.R. Almeida acknowledges CNPq-Brazil and FAPEMIG (grant number APQ-00062-22).

Conflicts of Interest

The authors declare no conflict of interest.

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Civileng 03 00061 g001 550
Figure 1. Particle size distribution of precursors GGBS, CS, and SAPs by laser diffraction.
Figure 1. Particle size distribution of precursors GGBS, CS, and SAPs by laser diffraction.
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Figure 2. Water absorption capacities of SAPs up to 3 h.
Figure 2. Water absorption capacities of SAPs up to 3 h.
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Figure 3. Water absorption capacities of SAPs up to 24 h.
Figure 3. Water absorption capacities of SAPs up to 24 h.
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Figure 4. Workability of mortars by flow table.
Figure 4. Workability of mortars by flow table.
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Figure 5. Setting times results by Vicat test.
Figure 5. Setting times results by Vicat test.
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Figure 6. Autogenous shrinkage of samples without SAP.
Figure 6. Autogenous shrinkage of samples without SAP.
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Figure 7. Autogenous shrinkage of 100% GGBS samples.
Figure 7. Autogenous shrinkage of 100% GGBS samples.
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Figure 8. Autogenous shrinkage of 75% GGBS samples.
Figure 8. Autogenous shrinkage of 75% GGBS samples.
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Figure 9. Autogenous shrinkage of 50% GGBS samples.
Figure 9. Autogenous shrinkage of 50% GGBS samples.
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Figure 10. Results of compressive strength of mortar in different ages.
Figure 10. Results of compressive strength of mortar in different ages.
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Table
Table 1. Chemical composition of GGBS and CS (Source: manufacturers).
Table 1. Chemical composition of GGBS and CS (Source: manufacturers).
ElementGGBS (%)CS (%)
CaO40.043.90
SiO236.0137.30
Al2O310.031.68
Fe2O30.5038.80
MgO8.012.09
SO30.20-
K2O0.70-
Na2O0.41-
Cr-0.22
Cu-0.70
Zn-0.78
Table
Table 2. Mix compositions of the samples.
Table 2. Mix compositions of the samples.
SampleSand
(g)		GGBS
(g)		CS
(g)		Water
(g)		Sodium
Silicate (g)		SAP C
(g)		SAP E
(g)
100G200100033.3436.5100
75G200752533.3436.5100
50G200505033.3436.5100
100GC200100033.3436.510.250
75GC200752533.3436.510.250
50GC200505033.3436.510.250
100GE200100033.3436.5100.25
75GE200752533.3436.5100.25
50GE200505033.3436.5100.25
Table
Table 3. pH measurement of alkali GGBS-CS solutions with and without SAPs during teabag test.
Table 3. pH measurement of alkali GGBS-CS solutions with and without SAPs during teabag test.
SAP C Measurements
Time100% GGBS75% GGBS50% GGBS
MinutesHoursSAP CRefSAP CRefSAP CRef
180312.2912.4712.6212.8212.4412.67
14402412.3112.1712.6512.5712.5012.42
SAP E Measurements
Time100% GGBS75% GGBS50% GGBS
MinutesHoursSAP ERefSAP ERefSAP ERef
180312.3112.4412.7312.8612.6212.71
14402412.3312.2612.6712.5312.5212.44
Table
Table 4. Percentage change in workability of reference samples by addition of CS.
Table 4. Percentage change in workability of reference samples by addition of CS.
SampleCS ContentFlow (mm)Flow Reduction by CS Addition
100G0%168-
50G25%1595.4%
75G50%12923.2%
Table
Table 5. Percentage change in workability of samples with addition of SAP.
Table 5. Percentage change in workability of samples with addition of SAP.
SampleType of SAPFlow (mm)Flow Reduction by SAP
100G-168-
100GCSAP C1538.9%
100GESAP E1569.6%
75G-159-
75GCSAP C1486.9%
75GESAP E14111.3%
50G-129-
50GCSAP C1253.1%
50GESAP E1225.4%
Table
Table 6. Percentage change in compressive strength results by addition of SAP at 6 months. Negative values indicate the reduction in compressive strength, and positive values indicate the increase in compressive strength, compared to the respective reference samples (without SAP).
Table 6. Percentage change in compressive strength results by addition of SAP at 6 months. Negative values indicate the reduction in compressive strength, and positive values indicate the increase in compressive strength, compared to the respective reference samples (without SAP).
GGBS ContentCS ContentSAP CSAP E
100%0%−7.1%−2.3%
50%25%−6.7%+7.3%
75%50%−10.6%+8.8%
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MacLennan, S.; Almeida, F.C.R.; Klemm, A.J. The Effect of Superabsorbent Polymers on Mechanical Characteristics and Cracking Susceptibility of Alkali-Activated Mortars Containing Ground Granulated Blast-Furnace Slag and Copper Slag. CivilEng 2022, 3, 1077-1090. https://doi.org/10.3390/civileng3040061

AMA Style

MacLennan S, Almeida FCR, Klemm AJ. The Effect of Superabsorbent Polymers on Mechanical Characteristics and Cracking Susceptibility of Alkali-Activated Mortars Containing Ground Granulated Blast-Furnace Slag and Copper Slag. CivilEng. 2022; 3(4):1077-1090. https://doi.org/10.3390/civileng3040061

Chicago/Turabian Style

MacLennan, Stewart, Fernando C. R. Almeida, and Agnieszka J. Klemm. 2022. "The Effect of Superabsorbent Polymers on Mechanical Characteristics and Cracking Susceptibility of Alkali-Activated Mortars Containing Ground Granulated Blast-Furnace Slag and Copper Slag" CivilEng 3, no. 4: 1077-1090. https://doi.org/10.3390/civileng3040061

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