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

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.