Surface Reactivity of Cementitious Crystals Alite and Belite

A fundamental understanding of why alite undergoes faster hydration compared to belite is developed in this manuscript through a dispersion-corrected first principle based simulation study. Consideration of dispersion correction gives a better correlation of lattice parameters with experimental observations as well as results in changes to the relative ordering of surface energy of these materials. A new methodology is presented to quantitatively estimate and compare the global surface reactivity of these two materials using concepts of chemical potential, chemical hardness, change in the number of electrons in the system, and change in energy. Underlying insights for reactive sites on each surface are determined through local reactivity parameters such as condensed atom variants of Fukui indices representing the propensity for a nucleophilic or electrophilic attack. Apart from providing a detailed fundamental understanding of why alite undergoes faster hydration compared to belite, the study presents a methodology for assessing the reactivity of a crystal surface without the need of introducing any foreign moiety near the surface.