Resistance of Alkali-activated Slag Cement Against Sodium Sulfate

This work evaluates the resistance of alkali-activated slag (AAS) mortar against sodium sulfate attack. The effects of immersion in 5% sodium sulfate solution under room temperature and wetting-drying cycles on the compressive strength of mortar specimens were considered to evaluate the extent of degradation. Mortar specimens prepared from type II and V Portland cements (PC2 and PC5) in accordance with ASTM standard were also used as a reference. To characterize the chemical products of the degradation process due to sodium sulfate attack, the specimens were also studied by X-ray diffractometry, scanning electron microscopy, and the elemental analysis by energy-dispersive X-ray spectroscopy. After 360 days of exposure to the sodium sulfate solution, PC2, PC5 and AAS cements showed 71, 52 and 45% reduction in compressive strength, respectively. According to the obtained results, AAS cement exhibits a higher sulfate resistance compared to PC2 and PC5.