Rheology, calorimetry and electrical conductivity related-properties for monitoring the dissolution and precipitation process of cement-fly ash mixtures

Abstract

The process of dissolution and precipitation of hydrated cement-fly ash mixtures is the basis of rheological behaviour and the establishment of mechanical strength over time. In this paper, the dissolution and precipitation process of cement-fly ash mixtures was monitored by rheology, calorimetry and electrical conductivity measurements.Two FAs supplied from different thermal power stations are used.The physical and chemical properties of FAs, including particle size and glassy phase, are shown to have various effects on the rheology and hydration kinetics of modified cement pastes.Calorimetry and electrical conductivity findings are in agreement to corroborate the dissolution process during the first minutes of hydration, followed by the precipitation of hydrated products, mainly portlandite, during the acceleration period. The addition of FAs leads to the prolongation of the dormant period and the slow dissolution of cement species by diffusion through the formed hydrate layer around the surface of cement particles. • Cement partially (10, 20, 30, 40%wt) replaced with altered FAs. • FA type affected the hydration degree and electrical conductivity. • The rheological properties are more related to the FA particle size. • The glassy phase has higher influence on the mechanical performance than the fineness of FA.