The hydration of slag in complex binder and the microstructural variation of hardened paste under the condition of leaching of soft water

Abstract

The hydration of slag in complex binder with different dosage was studied by identifying Ca(OH)2 content in hardened paste and Ca/Si ratio of formed C-A-S-H gel. The results shows that: elevated temperature curing could improve the slag’s reaction degree in early ages, but hinder the further hydration in late time. Some Ca(OH)2 is consumed when the outer hydrate is formed in early hydrating time, so the Ca(OH)2 content in the hardened paste decreases and Ca/Si ratio of C-A-S-H gel decreases. In the late hydrating time, the inner hydrate is formed, it no longer consumes a significant amount of Ca(OH)2, then Ca/Si ratio of C-A-S-H gel decreases more and Ca(OH)2 content tends to increase in the hardened paste. The Ca(OH)2 content in pastes is abundant, the Ca/Si ratio of C-A-S-H gel slightly decreases but there is not the decomposition sign of C-A-S-H gel after leaching of soft water for long time. The porosity of cement-slag complex binder pastes is low. The cement-slag complex binder containing no more than 70% slag shows good leaching resistance