Quantifying the effect of temperature on belite hydration kinetics through quasi in situ XRD

Belite-rich cement is a promising low-carbon material, yet the limited hydraulic reactivity of its primary component, dicalcium silicate ($\beta$-Ca₂SiO₄), still poses a challenge. This study introduces a new approach to examining the reaction kinetics and acceleration strategies for low-reactivity materials like $\beta$-Ca₂SiO₄ using quasi in situ X-ray diffraction (XRD). By simultaneously analyzing pre-cured and fresh samples, the method reduces measurement time at the expense of lowering temporal resolution. Applying this technique to hydrating $\beta$-Ca₂SiO₄ pastes from 21 to 80 °C provides insight into the underlying temperature-dependent dissolution process and its apparent activation energy (AAE). The estimated AAE of 49 ± 3 kJ/mol aligns with existing data and supports the view that the rate-limiting step of belite hydration may change based on the physical properties of the material. By offering phase-specific and time-resolved data, this method serves as a useful tool in devising science-informed strategies to accelerate hydration of belite-rich cements.