Swelling and compressibility characteristics of bentonite and kaolin clay subjected to inorganic acid contamination

Increasing number of failures of industrial structures due to distress caused by acid contamination of foundation soils prompted the present study. This study examines the effect of highly concentrated inorganic acids on the swelling and compressibility characteristics of commercially available bentonite and kaolin clay. Two concentrations of sulphuric acid and phosphoric acid are used as pore fluids. Experimental results showed that bentonite specimens contaminated with both acids exhibited significantly lower swelling and compressions than uncontaminated bentonite. Decrease in double layer due to replacement of sodium cations by hydrogen ions is responsible for lower swelling and compressions. On the other hand, kaolin clay exhibited higher swelling with both acids than uncontaminated kaolin clay. However, compressibility marginally increased with both sulphuric acid and phosphoric acid. Formation of flocculant fabric along with mineral dissolution is responsible for deviations in compressibility behaviour of contaminated kaolin clay. The structural alteration due to acid contamination was examined by FT-IR spectroscopy.