Effect of polymer latex powder on shrinkage behaviors and microstructure of alkali-activated slag binder

Alkali-activated slag (AAS) cements usually exhibit larger shrinkage than the ordinary Portland cements. This study investigated the effectiveness of styrene acrylate copolymer latex powder addition in mitigating the shrinkage behavior of AAS binders. The results showed that the one-dimensional autogenous shrinkage of the binder with 2 wt% latex addition was decreased by 47.6%. The latex addition compacted the pore structure of binder to restrict the moisture evaporation, contributing to the mitigation of drying shrinkage. The proportion of capillary pores (10–50 nm) in the matrix was also reduced, resulting in a lower capillary pressure development. The less gel pores imply that the chemical shrinkage of paste with latex is relatively weak. Not only would the inert latex gains embedded in the matrix hinder the microcrack development but it also enhanced the bonding performance in the binder. It should be noted that the binder with 0.5 wt% latex addition exhibited the lowest drying shrinkage. This was also mainly attributed to the dilution effect brought by the inert latex grains, which enhanced the availability of activator for per unit volume of slag particles, and thus enhanced the degree of alkali activation in the binder.