Sulfate resistance and hydration products of steam cured steel slag blended cement mortar under dry–wet cycle

Abstract

In this investigation, the dry–wet-cycled sulfate resistance and hydration products of steam-cured and standard-cured steel-slag mortars were investigated. Strength loss, porosity change, and microstructure of mortars prepared by replacing 20% of cement with steel slag (SS) were analyzed and compared with pure cement (PC) mortars. The results revealed that SS-blended cement mortar shows worse sulfate resistance than PC mortar regardless of the initial curing condition. Steam-cured PC mortar presents inferior sulfate resistance to standard-cured PC mortar, on the contrast, steam curing improves the sulfate resistance of SS mortar, when compared with the standard-cured mortars. Besides the large amount of C-S-H gels, the formation of hemicarbonate, C-A-S-H and relative lower CH content under steam curing can account for the improved sulfate resistance of initially steam-cured SS mortars, although the high porosity caused by steam curing brings negative impact to the sulfate resistance.