Contamination of soils is a critical problem as a result of malfunctioning industries like possible leakage and inferior disposal of wastes. The leakage and spillage of acids infiltrate to the ground and cause swelling of the foundations because of their reaction with the active minerals in the soils. Calcareous soils are widely used in construction. Hence, the carbonate soils are liable to volumetric changes when contaminated with acids. The current work examines the effect of the changes of volume as well as the microstructure of calcareous soils when infiltrated by different concentrations of phosphoric acid. The samples of soil were equipped with molds of acid resistance high-density polyethylene. The volume change was measured by the linear variable differential transformer. The compositional analysis was performed for the acid-contaminated samples. The results indicate there is a volume change with varying the acid concentration, however, silty clayey sand exhibited extensive expansion. This can be attributed to the severe reactions of phosphoric acid and carbonate mineral and the products blocked off the passage for the acid to permeate to the other parts of the soil sample as evidenced by the morphological and compositional analysis of the contaminated samples. (C) 2019 Elsevier B.V. All rights reserved.