Portland cement-blast furnace slag mortars activated using waterglass: – Part 1: Effect of slag replacement and alkali concentration

Mortars of PC replaced with 0% to100% blast furnace slag were activated by waterglass at 0–10 wt.% of Na2O, aiming to investigate the effect of the alkaline activation in reducing the low early strength observed in Portland cement–slag blends. For the activated blended mortars, increased %Na2O and slag contents favored strength; 80% slag showed favorable results with 6 and 10%Na2O, while 30–50% slag, the presence of the alkaline activator was unfavorable relative to the non-activated Portland cement and slag mortars. The microstructures showed denser matrices of hydration products as the amount of slag and alkali concentration were increased, corresponding to the strength observations.

► The activation of mortars of Portland cement with slag was investigated to reduce the low early strength.
► For mortars with 50–30% slag, the activation with water glass (4–10%Na2O) was not effective.
► For 80% slag the activation with 4–10%Na2O was effective.
► The highest strengths were for activated 100% slag cements.