Microstructural and Geotechnical Evaluation of Cement-Stabilized Crude Oil-Contaminated Silty Clay

Abstract

This study assessed the performance of Ordinary Portland Cement (OPC) in stabilizing crude oil-contaminated silty clay soil with special focus on the improvement of the geotechnical and microstructural properties. Geotechnical tests were conducted on soil samples contaminated with crude oil at concentrations up to 20% and stabilized with cement contents from 6% to 10%. The geotechnical properties investigated were void ratio, compressibility, California Bearing Ratio (CBR) and unconfined compressive strength (UCS). Furthermore, Scanning Electron Microscopy (SEM) was used to characterize the microstructure changes in the soil. The results indicated that crude oil increased the initial void ratio and compression index by 18.3% and 47.6%, respectively, and decreased the CBR by 43.1% and soil cohesion by 40%, mainly due to the lubricating effect of oil on soil particles. The addition of OPC as a stabilizing binder promoted pozzolanic reactions, which resulted in an 11–24% reduction in void ratio under an applied stress of 710 kN/m2 and a 7.7–21.5-fold increase in UCS compared with the untreated contaminated soil. SEM analysis of the soil with 10% cement showed the formation of continuous C–S–H matrices around the oil droplets, and hydraulic conductivity was decreased by about 1.5 times. The results showed that the application of OPC can significantly improve the mechanical stability and microstructure of oil-contaminated silty clay, and therefore confirm the feasibility of using it as a soil stabilizer for environmental rehabilitation.