Use of alkali activated high-calcium fly ash binder for kaolin clay soil stabilisation: physicochemical evolution

This study addresses the use of alkali activated high-calcium fly ash-based binder to improve engineering characteristics of soft clay-rich soils as an alternative to common stabilisers. The physico-chemical reaction sequence has been investigated by considering the binder alone and the binder mixed with kaolin. An insight into the reactivity evidenced that calcium-containing phases derived from high-calcium fly ash represent the reactive phases and, hence, pozzolanic activity is the dominant process. New compounds are formed, thenardite Na₂SO₄ and an amorphous silicate consisting of chains combined with calcium probably incorporating three-dimensional four-fold aluminium environments.