Effects of Used Engine Oil on Production of High-Strength Concrete

Abstract

This research addressed the dual challenge of sustainable waste management through the reuse of used engine oil and the continuous demand for innovative high-strength concrete (HSC) production methods. The aim of this study was to investigate the effects of used engine oil on production of high-strength concrete. A detailed set of experiments was conducted involving the production and testing of full-scale reinforced concrete beams. The beams were cast using concrete mixes with a controlled dosage of superplasticizer, and their performance was compared with that of test mixes produced using varying dosages of used engine oil. The tests included fresh concrete properties such as slump and air content, as well as hardened properties including compressive, flexural, and splitting tensile strengths. The data obtained from the experimental tests underwent comprehensive analysis. This included plotting load–deflection curves and assessing the compressive strength, flexural strength, and tensile strength of both the control and test beams, cubes, and cylinders. Cracking patterns were also documented. At 56 days, the control mix achieved a compressive strength of 53.8 MPa, while mixes containing 0.15% and 0.30% used engine oil recorded 39.2 MPa and 25.7 MPa, representing reductions of 27.14% and 60.1%, respectively. The slump values increased from 210 mm (control) to 230 mm and 240 mm, showing a 9.52% –14.29% improvement in workability. The flexural strength load decreased from 57.08 kN (control) to 52.65 kN and 43.11 kN, indicating reductions of 7.76% and 24.47%, respectively. Similarly, splitting tensile strength loads changed from 96.48 kN (control) to 105.29 kN and 92.72 kN, showing a slight increase at 0.15% but a minor drop at 0.30%. The findings indicate that the incorporation of used engine oil enhances the workability of high-strength concrete but leads to a significant reduction in compressive and flexural strengths as the dosage increases. A low dosage of 0.15% used engine oil provided a limited improvement in workability and splitting tensile performance, though with a noticeable compromise in compressive strength, while a 0.30% dosage proved detrimental to overall mechanical performance. Consequently, used engine oil is not suitable as an admixture for high-strength structural concrete where strength is critical, but may be cautiously considered at very low dosages for non-structural applications where improved workability and sustainability benefits are prioritized.