Abstract
In this study, internal curing by superabsorbent polymers (SAP) is utilized to mitigate self-desiccation and autogenous shrinkage of alkali-activated slag (AAS) pastes. Absorption and desorption kinetics of SAP incorporated in AAS pastes were studied with X-ray tomography. Internal curing delayed the peak of the rate of heat liberation but increased the total reaction degree of AAS pastes. Internal curing by SAP mitigated effectively the drop of internal relative humidity and the self-desiccation-induced autogenous shrinkage of AAS pastes. The cracking tendency of AAS pastes undergoing shrinkage in restrained conditions was also significantly reduced with SAP. Nonetheless, adding SAP, regardless of their content, cannot eliminate the autogenous shrinkage of AAS pastes, suggesting the existence of other autogenous shrinkage mechanism(s) besides self-desiccation.
Highlights
Slag based alkali-activated materials have emerged as eco-friendly alternatives to binders based on ordinary Portland cement (OPC) [1]
Several drawbacks of activated slag (AAS), such as fast setting and large shrinkage, limit a wide application of this material in engineering [8,9]. It has been reported in the literature that mixtures based on AAS can exhibit several times higher autogenous shrinkage than mixtures based on OPC [10]
This study aims at exploring the effectiveness of internal curing by superabsorbent polymers (SAP) in mitigating the autogenous shrinkage and the early-age cracking of AAS
Summary
Slag based alkali-activated materials have emerged as eco-friendly alternatives to binders based on ordinary Portland cement (OPC) [1]. Compared to Portland cement, alkali-activated slag (AAS) entails around 25–50% lower CO2 emissions and more than 40% lower embodied energy in the production process [2,3]. Several drawbacks of AAS, such as fast setting and large shrinkage, limit a wide application of this material in engineering [8,9]. It has been reported in the literature that mixtures based on AAS can exhibit several times higher autogenous shrinkage than mixtures based on OPC [10]. The high autogenous shrinkage of AAS can increase the cracking potential of the concrete [11]
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