Effects of the heterogeneous hydration of alkaline-earth aluminosilicate glasses on phase evolution in hardened blended cement paste

Supplementary cementitious materials (SCMs) affect the hydration process and long-term properties of cementitious systems. Since a large percentage of SCMs belong to alkaline-earth aluminosilicate glasses that possess a phase-separated structure, further research into their hydration characteristics is essential. This study investigated the effects of the hydration characteristics of synthetic glasses with various phase-separated structure on the phase evolution of cementitious systems by combining simulations with experiments. The results showed that with the increasing degree of phase separation, the hydration of synthetic glass transitions from homogeneous to heterogeneous hydration. The phase evolution of hardened paste, particularly for calcium hydroxide, is influenced by the difference in hydration rates among each separated glassy phase. Compared to homogeneous hydration, the rapid hydration of the Ca-rich phase reduced the consumption of calcium hydroxide, while the rapid hydration of the Si-rich phase accelerated calcium hydroxide consumption. For glasses exhibiting phase separation characteristics, the consistency between thermodynamic simulations employing a heterogeneous hydration model and experimental results exhibits a notable enhancement.