Modification of Expansive Clay Behavior by Using of the Filtration Effluent of the Water Treatment Plant

Document Type


Publication Date



Many studies have been conducted on using additives to modify the behavior of expansive clay, given the significant structural damage caused by dispersive and swelling clay. This study investigated the effect of ferric chloride on dispersive clay properties. Owing to the presence of polyvalent cations, ferric chloride, used as a coagulant in water treatment, reduces the thickness of clay's double layer through cationic exchange and decreasing water absorption. Ferric chloride was added to the soil at four levels (1, 2.5, 5, and 7.5%), and Atterberg limits, permeability, pH, and unconfined compressive strength tests were conducted to evaluate the effect of this substance on the swelling properties of soil. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests were conducted to obtain the results. The results show that adding this substance increased the compressive strength up to 2.5%, confirming the viability of using ferric chloride as a non-traditional and an environmentally friendly additive.


Original published version available at

Publication Title

Iranian Journal of Science and Technology, Transactions of Civil Engineering