First-Principles Approach to Water Adsorption Properties of Belite with Dopants

Belite-rich cement is beneficial to low-heat liberation, strength development at a later age, and reduction of environmental impact in clinkerization process. However, this cement has to compromise on the lower hydraulic activity at an early age. This study theoretically investigates the effect of additional incorporation of S and P atoms into Mg-doped beta-form belite (beta-C2S) on the improvement of water adsorption ability of Mg-doped beta-C2S having low hydraulic reactivity by first-principles calculations. The numerical simulation based on density functional theory shows that the additional co-doping of S and P into Mg-doped beta-C2S dramatically enhances the absolute value of initial water adsorption energies on beta-C2S surface two to four times as much as that of Mg-doped beta-C2S. The contribution of S and P to reactivation is theoretically proved in PDOS analyses, and the calculation results corroborate with the strength development properties of cement paste containing the synthesized Mg-doped beta-C2S with SO3 and P2O5.