Modelling and visualizing the impact of metakaolin on the alkali concentration in cement paste pore solution

Abstract

This study investigates the effects of replacing Portland cement (PC) with metakaolin (MK) on the pore solution composition of cementitious binders. Using the empirical Taylor model and a thermodynamic model (GEMS), the required replacement levels of PC by MK are computed to achieve different threshold alkali metal concentrations. GEMS predicts that similar amounts of MK (15–20 %) are required regardless of w/b-ratio and PC alkali content, which does not match with the experimental evidence. The Taylor model captures better the effect of these variables, predicting replacement levels ranging from 0 to 40 %. Results are visualized through contour and 3D plots, highlighting the complex interactions and effects of SCMs on concrete durability.