Investigation of the Cause of Disintegration of Alkali-Activated Slag at Temperature Exposure of 50°C

Abstract

Tests reported in this paper show that alkali-activated slag paste (AASP) can totally disintegrate when exposed to oven drying at 40–50°C with circulating air. This phenomenon has not been previously reported in the literature. Further tests eliminated two possible reasons for the disintegration: (1) carbonation of calcium-silicate-hydrate (C-S-H) gel leading to loss of strength and (2) differential shrinkage and cracking leading to disintegration of the samples. Thermal gravimetric analysis (TGA) confirmed that maximum mass loss of about 18% occurred at approximately 40°C. It is postulated that the mass loss is attributed to the loss of chemically-bound water resulting from the disintegration of C-S-H gel and strength loss. This conclusion is arrived in this paper by the process of elimination. Disintegration of AASP at this relatively low temperature is a serious issue and warrants further research on exact cause and possible remedies.