Portland cement-blast furnace slag mortars activated using waterglass: Effect of temperature and alkali concentration

Abstract

Mortars of portland cement with 50% of blast furnace slag were alkali activated with 0–10%Na2O using waterglass and cured at 10–40°C. The presence of the slag reduced the strength of 0%Na2O blends and the alkaline activation with 4%Na2O resulted in even lower values; 6%Na2O gave similar results as 0%Na2O and 10%Na2O rendered strengths similar or higher than those of neat portland cement. The combination of higher temperature and higher alkalinity favored the reactivity and strength. The formation of N–C–S–H and delayed hydration of portland cement appeared to be the causes of the low strengths observed in alkali activated systems.