First-principle insights of initial hydration behavior affected by copper impurity in alite phase based on static and molecular dynamics calculations

Copper tailings have been used as a raw material for cement clinker production. The Cu element can enter into the cement phase and change its hydration behavior. In this study, the influence of Cu-doping on the structure and hydration characteristics of alite phase (tricalcium silicate, C3S) are disclosed by combining the density functional theory (DFT)-based static and molecular dynamics calculations. In the static simulation, local Oi atoms move closer to doped Cu atom with Cu-O distance of 1.84-1.93 angstrom and forms Cu-Oi bonds, resulting the decrease of surface electrophilic reactivity. A single water molecule exhibits lower adsorption energies (0.92-2.12 eV) on the Cu-doped C3S surface than on the pure C3S surface (0.62-1.69 eV), as the chemical bonds of Ca-OW and HW-OS were weakened. Further ab-initial molecular dynamics (AIMD) simulations cover the shortcomings of static calculations and obtain new discoveries: (a) Cu-doping promotes hydroxylation of C3S surface and stabilizes fluctuation of dissociated proton. (b) Ca-OW bond concentration is raised after Cu-doping, whereas the constraint effect of the C3S surface on OW is weakened. (c) Cu-doping accelerates the diffusion of Oi into water layer by similar to 2 angstrom within 13 ps, facilitating the dissolution of clinker. These findings contribute in several ways to our understanding of the hydration properties of Cu-doping C3S and provide theoretical support for the sustainable and greener development of the construction industry.