Understanding why Alite is responsible of the main mechanical characteristics in Portland cement

We provide here a full analysis of the ground state properties of Tricalcium silicate Ca3SiO5 (C3S) by means of density functional theory. Elastic behaviour of C3S was characterized by considering the stable phase and anisotropy of this material. Moreover, the electronic structure is determined in order to get an insight into the reaction mechanism of C3S. Local density of states (LDOS) of valence band maximum (VBM) and conduction band minimum (CBM) are analysed to characterize reactive sites of C3S. Two oxygen atom-types were distinguished from the charge density of the system. LDOS of VBM is highly localized explaining the observed high reactivity of C3S under electrophilic attacks (e.g. H+). In addition, reactive sites under electrophilic attacks are noticed to be only around some specific oxygen atoms. In contrast, the analysis of LDOS for CBM suggests that some calcium atoms are responsible for undergoing reaction with anions such as hydroxide ion.