Effect of curing temperature on hydration, microstructure and ionic diffusivity of fly ash blended cement paste: A modelling study

Abstract

This paper presents an integrated modelling framework to investigate the effect of curing temperature on hydration, microstructure and ionic diffusivity of fly ash blended cement. A 3D cement hydration model, i.e. CEMHYD3D, was modified by incorporating the parameters representing the temperature-dependent dissolution of Portland cement and fly ash and then used to simulate the hydration and microstructural evolution of blended cement with different fly ash replacement ratios and types and water-to-binder ratios cured at various temperatures. Based on the generated 3D microstructure, a lattice Boltzmann model for diffusion was employed to simulate the ionic diffusivity and estimate the relationship between ionic diffusivity and microstructure in hydrating fly ash blended cement paste. Results indicate the simulated hydration process of blended cement cured at various temperatures agrees well with experimental data. The elevated curing temperature leads to a lower capillary porosity and connectivity, less diffusible C-S-H and lower ionic diffusivity at early ages but higher ionic diffusivity later due to the denser hydration products in fly ash blended cement paste.