Reaction Kinetics, Modeling, and Analysis of Ground Granulated Blast Furnace Slag Hydration in Model Systems

ABSTRACT Hydration temperature and particle size strongly influence the reaction kinetics of supplementary cementitious materials (SCMs). This study focuses on quantifying and modeling these effects on ground granulated blast furnace slag (GGBFS) hydration in the R 3 model system. Particle size fractions ( d 50 5.3–40.0 µm) and curing temperatures (20°C–40°C) typical of cement hydration were investigated. The GGBFS degree of reaction (DoR) was systematically assessed using selective dissolution, with careful verification of method selectivity, providing a robust basis for model calibration. The kinetic model is based on a classical shrinking core approach with coupled reaction stoichiometry to simulate phase assemblage evolution and provides a transferable framework readily applicable to other systems. Experimental results showed that hydration kinetics was strongly accelerated by increased temperature and finer particle size, both of which increased reactivity. At later ages, all systems converged toward a similar ultimate DoR, indicating an inherent limitation in hydration extent. Analysis of rate‐controlling factors coupled to microstructural observations showed that reaction deceleration at higher degrees of reaction coincided with the formation of a dense hydrotalcite rim. This evolution, together with decreasing activation energies coupled to calorimetric and microstructural evidence, suggests a progressive shift in the reaction rate controlling mechanism.