Resistance of alkali-activated slag to sulphate attack and elevated temperatures

Abstract

Thermal stability as well as sulphate resistance of alkali activated slag (AAS) pastes prepared from Ground Granulated Blast Furnace Slag (GGBFS) and 5% fly ash (FA)are examined. AAS pastes are accelerated using alkaline solution of sodium hydroxide with concentration 1, 1.5 and 2 M and sodium silicate with fixed concentration (0.28 mol/Kg).AAS pastes exposed to 5% MgSO4 solution and to high temperature (200, 400, 600 and 800 oC). The compressive strength, bulk density, total porosity, chemically combined water content and phase composition are determined in this study. Concentration of 2M NaOH with 5% FA promotes the best properties of AAS pastes that exhibit the highest resistance to firing up to 400oC by achieving the greatest compressive strength. However, AAS pastes activated by 2M NaOHgive a high sulphate resistance.