Micro-fabric and mineralogical studies on the stabilization of an expansive soil using inorganic additives

This paper describes the microfabric and mineralogical changes in an expansive soil from Siruseri (South-East Chennai, Tamilnadu, India), when treated with inorganic additives such as Calcium Hydroxide and Calcium Chloride. The engineering and index properties and mineralogical composition of the untreated and treated soil were determined. The soil particles have been found to get altered and new products are formed in the case of the calcium hydroxide treated samples. The fabric becomes more flocculated and the microfabric results indicate the formation of new aggregations and bindings due to the addition of the stabilizer. The X-ray diffraction tests on the treated samples indicated a shift in the basal spacing and reduction in peak intensities which is due to the formation of the flocculated structure. This shows that the stabilizing effect of an effective additive brings a change in the microfabric and mineralogy, which causes a change in the engineering and index properties of the original soil. The effects of both the stabilizers are studied and a comparative study is made. Calcium hydroxide brings more desirable effects due to the pozzolanic reactions and formation of cementitious products such as the calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH). The addition of CaCl2 makes the soil denser and forms denser clay matrices and there is no pozzolanic reaction. In order to cater the problem of solubility in the case of lime column usage for deeper depths, attempt was made to study the influence of the addition of lime solution to the expansive soil. The addition of lime solution reduced swelling but the engineering properties did not change significantly.