Experimental evaluation of kaolin stabilised with class F fly ash

This study aims to investigate the effectiveness of fly ash (FA) in stabilising a kaolin soil through laboratory tests. Kaolin is an example of moderate plasticity clays that require stabilisation methods for construction purposes. The influence of FA on the improvement of kaolin is studied by varying its dosages in the mixtures (0%, 10% to 20%) as well as the cement content, used as an activator in different percentages (5 and 7%). The influence of the dry unit weight and the curing time of the soil mixture is also analysed through unconfined compressive strength and indirect tensile strength tests. The experimental results show that the strength increases linearly with both FA and cement contents. Moreover, higher initial dry unit weights also yield higher final strengths. To further assess the improvement, the application of the porosity over the volumetric cement content ratio, as the main variable, succeeded in attaining a relationship with the strength and the stiffness of the studied soil. Results for the combined effect of the porosity and the volumetric cement on the secant modulus were also determined. Furthermore, a unique relationship was obtained combining porosity, volumetric cement and FA content