Stabilisation of Sulfate-Rich Expansive Soils Using Wollastonite Powder: A Mineralogical Approach

Expansive soils with high sulfate content pose a serious challenge to the pavement infrastructure due to the rapid formation of expansive minerals like ettringite. The conventional calcium-based stabilizers, like lime and cement, often accelerate the ettringite crystal growth and result in sulfate-induced heave. Therefore, an alternative stabiliser that prevents these adverse chemical reactions is required. This study evaluates the potential use of wollastonite powder (CaSiO₃) as a sustainable stabiliser for sulfate rich soils. The research focussed on the physico-chemical and mineralogical changes of the wollastonite powder-treated soil matrix at varied curing periods and dosages. Atterberg limits were conducted to access the modification in plasticity properties of the stabilised sulfate-rich natural expansive soil. pH and EC of the treated expansive soil were measured at different time intervals to understand the balance between calcium and sulfate ions associated with wollastonite dissolution. X-Ray diffraction (XRD) analyses was performed at selected curing periods to study the minerological transitions and to detect the presence or absence of ettringite with time. These findings support the development of low-carbon sustainable binder as an alternative to the conventional stabilisers like lime in sulfate-rich environments.