Evaluation of castor oil as a Bio-plasticizer in concrete: effects on compressive and flexural strength

Abstract

Most of the research on enhancing concrete properties has concentrated on admixtures based on mineral oils which are not eco-friendly. This study presents the evaluation of a bio-based admixture (plasticizer), specifically castor oil on strength of concrete. M20 was designed and the dosages of castor oil adopted were 0.0%, 0.25%, 0.5%, 0.75%, and 1.0% according to the weight of the cement. A total of 138 samples were cast among which were 30 prisms (100 × 100 × 500 mm) and 108 cubes (100 × 100 × 100 mm). These samples were tested for flexural strength at 7 and 28 days, and for compressive strength at 3, 7, 28, and 56 days after curing in water under ambient conditions. The results revealed that higher castor oil dosages led to a reduction in compressive strength, particularly at 1.0%, which showed a 27.55% reduction at 7 days. But dosages up to 0.5% improved strength when water content was reduced. Specifically, the 0.25% dosage recorded an 8.45% increase in compressive strength compared to the control at 28 days. The admixture also improved flexural strength up to a dosage of 0.5%. Based on the findings, castor oil can be considered a bio-admixture in concrete, with 0.25% by weight of cement identified as the optimum dosage for application in plain concrete.