Internal curing by superabsorbent polymers in alkali-activated slag

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.The funding supported by China Scholarship Council under grand number 201506120072 and by Netherlands Organisation for Scientific Research (NWO) are acknowledged. The short visit at Empa by the first author was supported by the STSM project “Towards the next genera tion of standards for the service life of cement-based materials and structures” of COST Action TU1404. The funding provided by the Portuguese Foundation for Science and Technology (FCT) to the Research Project IntegraCrete (PTDC/ECM EST/1056/2014 - POCI-01-0145-FEDER-016841) is grateful acknowledged, as well as the grant UID/ECI/04029/2019 - ISISE, funded by national funds through the FCT/MCTES (PIDDAC)