Hydration of portland cement and slag cement mixtures with insights on AFm phases and reaction mechanism

Abstract

Hydration of Portland cement + slag blends with different slag replacements at various hydration times has been studied. Findings from QXRD, TGA, ESEM(EDS) & NMR have provided us with insights into the hydration mechanisms and phase assemblage of cement and slag mixtures. Phase assemblage and quantification of the AFm phases has been made possible using the parallel beam X-ray diffraction and it was observed that AFm formation is favored in these blends in direct proportion with the slag level. In fact, AFm formation after pozzolanic reaction can be considered as one of the consumers of portlandite in portland cement+slag blends. Hydrocalumite has been observed to be present among the hydration phases of these blends at various hydration times and its concentration has been observed to increase with increasing slag replacement. The presence of this phase might have implications on the durability aspects of the resulting concrete. Furthermore, some chemical reactions during slag hydration as well as its interactions with hydration of clinker phases have also been proposed.