Flexural properties of concrete using rubber tire crumbs

Currently, used tire rubber was widely used as a material replacement for coarse or fine aggregate in concrete, asphalt, and soil. The previous studies showed that the addition of rubber tire crumbs (RTC) in concrete could reduce the compressive strength and modulus of elasticity of concrete. This study observes the effect of RTC in the concrete mixture, on their flexural properties. The specimen is a concrete beam with a length of 60 cm and has a square cross-section of 15 cm x 15 cm. RTC is added as a partial substitute for sand, with the RTC contents of 0%, 5%, 10%, 15%, and 20% to the weight of sand. There are 2 variations of concrete mix design, which are 35 MPa and 17 MPa of concrete strength (fc’). The flexural strength test of the concrete beam was carried out on 10 specimens at 28 days old. The research found that the higher of RTC contents, the smaller the flexural strength of the concrete. The decrease in flexural strength is also influenced by concrete strength. The higher strength concrete will experience a smaller decrease in flexural strength caused by the increase of RTC contents. The concrete flexural strength decreased by an average of 56% on the 17 MPa, but 28% on the 35 MPa concrete strength (fc’). The results of this study can be used as a consideration in the application of the RTC concrete as a beam that withstands flexural loads.