Enhancing the Swelling Characteristics and Shear Strength of Expansive Soil Using Ferric Chloride Solution

Expansive soil has high tendency to swell and shrink with the change in moisture content. This phenomenon can cause excessive total and differential movements of overlying structures. Population growth has led to rapid urbanization that requires expansion of civil engineering infrastructures and the associated services. In Egypt, these types of soils are extensively found in many areas and it is virtually impossible to avoid construction on such soil. Recently, chemical stabilization became one of the most popular soil treatment techniques as they have the ability to dissolve easily in water. In this study, X-ray diffraction analysis, free swell index, modified Proctor compaction, consistency limits and swelling pressure of bentonite as a tested expansive soil were determined. Solid ferric chloride (FeCl3) is an inorganic highly ionizable material that can produce active trivalent iron compound (Fe3+) when mixed with water. In this study, the optimum percentage for ferric chloride solution was found to be 1%. At that percentage of ferric chloride solution, the free swell index and the swelling pressure for the expansive soil were reduced by 62% and 43%, respectively. Also, at 15% ferric chloride solution, the expansive soil plasticity index was reduced by 35%. Ferric chloride solution is a novel material that has not been used before in improving the behavior of expansive soil. This study demonstrates the effectiveness of the proposed method in stabilizing and improving the properties of expansive soil.