Assessment of the Impact of Oil-Contaminated Sand on the Structural Performance of Reinforced Concrete: Experimental and Numerical Analysis

This study presents a systematic investigation of the physical, chemical, microstructural, and mechanical properties of oil-contaminated sand (OCS) and the resulting concrete, alongside a structural evaluation of RC beams under monotonic loading. Sixteen groups of concrete cylinders were cast at oil contamination levels of 0–30% by weight of fine aggregate, and six RC beams were fabricated and tested at contamination levels of 0%, 4%, 8%, 12%, 16%, and 20%. Physical testing showed OCS has an increase of 249% water absorption and a decrease in specific gravity of 7.3% compared to clean sand. At 2% oil content, there was a slight improvement in all mechanical properties of concrete, but as the content increased, the concrete properties gradually and nonlinearly decreased; at 30% oil content, the concrete compressive strength, splitting tensile strength, modulus of rupture and modulus of elasticity, were reduced by 70.91%, 89.94%, 71.43%, and 44.84%, respectively. From a structural point of view, a 70% decrease in cracking load, 61.1% decrease in ultimate load and 60% decrease in the deflection capacity at midspan were observed with contamination increasing from 0% to 20%, and a fundamental transition in failure mode from ductile flexural to explosive brittle failure. The practical limit for structural applications is determined as 8-12% contamination.