This paper deals with the improvement of soil swelling for purposes of constructions by adding industrial waste Phosphogypsum (PG), in addition to the chemical additive sodium chloride (NaCl) to reduce its expansiveness and improve its characteristics for many earth work construction, the test results showed significant decrease in the swelling properties and pronounced reduction in the liquid limit, plastic limit and plasticity index of the clay by increasing the ratios of PG and NaCl. Also the results from x-ray diffraction (XRD) analyses of bentonit only and the mixture (1.2% PG+3% NaCl+95.8% Bent.) showed that, large amounts of Montmoronite clay mineral were approximately transformed to other phases during the reaction. Reaction products are non-swelling clay mineral commonly Kaolinite this is because, the mineralogy of both clay minerals reflects that, Montmoronite is an immature clay mineral while Kaolinite is a mature clay mineral. This maturity state may be attained through the chemical reaction with these additives. So, the PG industrial waste helps to improve the physical characteristics of soil swelling and the results present a very important factor for constructions purposes.