Autogenous Shrinkage of Alkali-activated Fly Ash-slag Pastes With and Without SAP

This paper presents an experimental study on mitigation of autogenous shrinkage in alkaliactivated fly ash-slag (AAFS) pastes by internal curing using superabsorbent polymers (SAP). A series of tests including workability, setting time, mechanical properties and autogenous shrinkage on AAFS pastes with various SAP dosages (0-0.5%) are conducted. The results indicate that the flowability and setting time of fresh AAFS pastes increase with the addition of SAP, while the compressive strength decreases with increasing SAP dosage. The chemical shrinkage and autogenous shrinkage of AAFS pastes are significantly reduced by the addition of SAP. As SAP dosage increases from 0.2% to 0.5%, the chemical shrinkage is reduced by around 18% to 45% while the autogenous shrinkage is decreased by about 76% to 85% compared to that without SAP. Moreover, internal curing using SAP is found to lower the heat peak and shift the peak to the right indicating the slower hydration rate corresponding to the lower chemo-mechanical deformation (chemical shrinkage), which contributes to the mitigation of autogenous shrinkage. Thus, internal curing by means of SAP is an efficient method for mitigating autogenous shrinkage in AAFS pastes