Used Oil as an Admixture to Improve the Rheological Properties of Concrete

In the past, industrial waste and by-products have successfully been used to improve the properties of concrete. Used engine oil is a waste product which is burdensome to discard of and, due to frequent replacement, is produced in high quantities in the construction industry. The utilisation of used engine oil in concrete has shown potential as an admixture by reducing slump and increasing air-content. The main disadvantage is a reduction in long term compressive strength. This study investigates used engine oil (UEO) and used hydraulic oil (UHO) as admixtures to concrete, focusing on its effect on the rheological properties. Slump, air-content, compressive strength and rheometer tests are conducted for concrete containing different dosages of UEO and UHO. Adding low dosages of UEO and UHO have no noteworthy effect on the compressive strength, although increasing air-content and altering the rheological properties significantly. UEO and, to a lesser extent UHO, reduced the energy required to initiate flow (static yield stress) as well as decreased the plastic viscosity. Adding UEO has a similar effect on the static yield stress and plastic viscosity as increasing water content or substituting cement with a proportion of fly-ash. In conclusion, UEO shows potential as an air-entrainer or water-reducing admixture.