Insights on the clay reactivity in alkaline media: Beyond filler role for kaolin

Abstract Beside lime and hydraulic binders, alkaline activation recently emerges as a possible solution for soil stabilisation. Unfortunately, soil reinforcement by alkaline activation requires additional reactive aluminosilicate sources under ambient temperature. In this study, we focus on kaolin as a simplified model of kaolin-rich soils which show limited improvement on mechanical performance after lime treatment. Here, we explore the reactivity of kaolin after a two-step process combining NaOH activation and sodium silicate solution activation. We show that kaolin reactivity is greatly enhanced compared to sodium silicate solution activation only. After the two-step process, the formed phases differ depending on the setup of the NaOH activation. More interestingly, for well chosen conditions, a large amount of highly depolymerized gel is created, which is expected to improve the mechanical performance of treated kaolin clay soils.