Expansive clays suffer very abrupt volumetric changes in the presence and absence of water, a synonym of instability that is reflected in technical and economic problems. The city of Los Mochis, Sinaloa, Mexico, has a high percentage of clays, which has been a challenge for engineers to build on unstable soil. Studies have been made with different soil stabilization techniques with different materials, such as lime, hydraulic cement, phosphates, aluminum salts and recently polymers. In this research we used the polymer diallyl dimethyl ammonium chloride (DADMAC), which is generally used as a flocculant polymer for water treatment.