Egypt has witnessed tremendous development in its infrastructure over the last decades. The problems of expansive soils seem to be overlooked during the design and construction of some of the projects. As a result, some houses and roads were demolished. In this study, soil samples were taken from New Sohag City (town in Upper Egypt). The physical and mechanical properties of the natural soil were obtained. Then the soil was treated with chemical additives (Addicrete P) 0.5%, 1% and 2% by dry weight of soil. After treatment of soil the properties of samples were investigated at different times. The main results show that with increase of Addicrete P Plastic limit increases and liquid limit decreases, hence decreases plasticity index. As the amount of additives is increased, there are apparent reductions in optimum moisture content, unconfined compressive strength, and free swell, swelling potential and swelling pressure, and a corresponding increase in maximum dry density and continue to increase or decrease over time. This study established optimum dosage levels for each of the treated additives. Based on the results obtained, it can be concluded that the expansive soil can be successfully improved by Addicrete P.