Dual dynamic regulation mechanism of trace calcium phosphate on hydration of cementitious materials and optimization of pore structure

This study explores the regulatory mechanisms of trace calcium phosphate (CaP) in the hydration of Portland cement. The results indicate that incorporating 0.001 wt% CaP extends the induction period by forming a passivation film while simultaneously accelerating the hydration rate during the acceleration phase as a nucleation agent, thereby improving hydration efficiency and uniformity. CaP enhances the polymerization degree and homogeneity of C-S-H gel. It modulates the formation and distribution of Ca(OH)₂, facilitating a controlled transition of the crystal structure from a chain-like configuration to layered or network-like forms, thereby enhancing stability. Furthermore, this study highlights the distinct roles of CaP in fresh and aged cement systems and proposes a multi-scale mechanism for complex hydration processes. These findings offer valuable theoretical insights and practical guidance for applying CaP in cementitious materials.