Effect of Sulfuric Acid on Swelling Behavior of an Expansive Soil

Soil often becomes contaminated with a variety of chemicals due to leakage of under/aboveground chemical storage tanks, improper discharge of waste, or improper design of waste containment facilities. Contaminated soil water can influence the soil's behavior seriously. Mineralogical alterations play a vital role in such circumstances. This paper describes the impact of varying concentrations of sulfuric acid solutions on the swell behavior of expansive soil containing predominantly montmorillonite. Using the conventional oedometer tests, the swell behavior of soil compacted with water inundated with acid solutions was studied. The soil swell, which is about 2% in water, increases to about 9% with 1N and to 50% with 4N acid solutions. The induced swell in acid solutions is attributable to mineralogical changes. The formation of new minerals and their associated fabric changes are investigated by scanning electron microscopy, X-ray diffraction, and energy dispersive analysis of X-ray on soil samples treated with sulfuric acid. While minerals like gypsum and kornelite are formed in the presence of 1N sulfuric acid, aluminite and chloritoid are formed in the presence of 4N sulfuric acid. These types of alterations are known to occur in iron sulfate minerals and are also found on Mars. The mechanism of mineralogical alterations is presented.