Thermodynamic modelling of cement stabilised soil

Soil stabilisation uses cement as a binder to improve the mechanical performance and durability of problematic soils. However, the underlying hydration of the cement and chemical behaviour combined with the soil’s influence is not well understood in these environments. This paper presents simulations of how the cement behaves in the soil-cement system using the pH Redox Equilibrium (PHREEQC) geochemical modelling software. The model incorporates the chemical description of the cement and soil using measured X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) data to simulate hydration reactions and provides predictions of the soil phase assemblages, pore solution chemistries and pH both over time and with increasing soil additions. The model therefore presents a geochemical-based predictive tool to optimise binder formulations and curing conditions in soil stabilisation applications. This model is then compared to physical data from a sample that has been stabilised to compare how the model aligns.