As the development progresses the need for agricultural products are also increasing day by day. For increasing the productivity more fertilizers have been used. As days passes population also increasing thus the accommodation is becoming problem, thus the uncultivated lands which were earlier cultivating used for construction. Chemicals in fertilizers may change the properties of soils and can affect the constructed structures. One of the most used fertilizer is the Rock phosphate, which is used as remineralising agent in cultivation. This study focuses on the detailed study of Rock phosphate and its effect on CL Clays.