Hydration activity, crystal structural, and electronic properties studies of Ba-doped dicalcium silicate

Abstract

High belite cement has a wide application potential due to its low energy consumption, low CO2 emission, and excellent durability performance. Due to the low hydration rate and strength development at an early age, the activation of beta-dicalcium silicate (β-C2S) crystallographic structure is essential to improve the early strength of high belite cement. In this study, the β-C2S phase is activated by dissolving Ba2+ ions into the crystal lattice to improve the hydration rate. Unlike the traditional analysis methods of thermodynamics and dynamics theory, the first principle and density functional theory were applied to study the effect of Ba2+ ions on the activation of β-C2S, especially on the crystallographic structure, lattice parameters, and electronic structure change. The crystallographic structure of β-C2S can be activated by doping Ba atom and the crystal formation energy increases and the bandgap between VBM and CBM become narrow in the activated β-C2S crystallographic structure. Comparing the Ca2+ substitution in [CaO6] or [CaO8], the lattice deformation and hydraulic reactivity is more significant in Ba2-C2S and Ba22-C2S. The first principle and density functional theory explains the change of the electronic structure of the activated crystallographic structure and provides a theoretical basis for the purposeful design of material structures.