Lime treatment of expansive soil like black cotton soil together with fly-ash and cement is known as calcium based treatment. The aim of this treatment is to alter clay mineralogy to have a better founding soil without significant swelling followed by shrinkage. This process of treatment results chemical reaction of exchanging ions of particles of clay mineral with positive species of ions. This process is called “cation-exchange” reaction.
Through the process of flocculation-agglomeration, this treatment clump tiny clay particles to form a larger particle. This process includes the reaction of positive charged particles with particles having negative charge.
Calcium based treatment also left cementing agent in the black cotton soil mass to form a soil mass of altered properties. The resulting effect of calcium based treated soil is a soil of reduced swelling and shrinkage potentials having better strength properties. In case of highway construction works this method is widely used.
|Octahedral sheet is sandwiched between two tetrahedral sheets to create the mineral structure of Black Cotton soil|
In India black cotton soils are found in over wide range of area. Highway construction works in most cases face this problem and the calcium based treatment is adopted. The Molecular Sandwich of Black Cotton Soil is discussed in previous post. Better understanding you can read this.