Volume change and microstructure of calcareous soils contaminated with sulfuric acid

Acid contamination of soils is a common problem within fertilizer and petrochemical industries. Soil properties could be altered due to acid contamination, especially the volume change within the vicinity of the contaminated soils. There are huge petrochemical and fertilizer industries in the industrial areas that produce or utilize different acids. Further, most of the soils used for road bases and under pavement and walkways are calcareous in nature. These carbonate soils are susceptible to large volume change when attacked by acids. This research aims to study the volume and microstructural changes using two calcareous soils, i.e. non-plastic and plastic marls, due to interaction with sulfuric acid at three different concentrations. The soil samples were prepared in high-density polyethylene (HDPE) molds that were placed in large containers and instrumented with linear variable differential transformer (LVDT) to measure the volume change. The morphology and composition analyses were studied utilizing scanning electron microscopy and X-ray diffraction. Results of this investigation indicate that the volume change and acid concentration were proportional except in the case with the non-plastic marl at high acid concentration. This was ascribed to the severe reaction of sulfuric acid with the carbonate minerals resulting in blocking the paths for further infiltration of the acid into the whole soil.