Effect of Crumb Rubber on Concrete’s and Mortar’s Structural Properties: A Review

Crumb rubber (CR) is a construction material obtained from slicing of scrap tyres. As reviewed, the inclusion of CR in concrete showed the reductions in concrete’s fresh and hardened properties even on its durability. This paper reports that CR-concrete is poor in workability, more porous, poor in resisting chlorine ion, inconsistency in strength and normally takes long time to set. Also, the review of previous results on CR-concrete proved that, CR-concrete’s ductile strength increased by 86.2% while its compressive, tensile and flexural strengths, and modulus of elasticity reduced by 50.3%, 24.51%, 31.94% and 23.51% respectively. The reduction in strength was tagged to the application of high percentages of CR in concrete (0–40%) and the use of high water–cement ratio (w/c) for the concrete production (≥ 4.0). Likewise, the microstructural results also support the strengths reduction trend. As reviewed, the inclusion of treated crumb rubbers in concrete improved its microstructural properties. Therefore, it is advisable to make use of the treated CR, 0–5% of CR and 0.4 water–cement ratio for the production of CR-concrete and mortar for better results. This data is available for future researchers to make further investigations on improving the weak reinforcing properties of Crumb Rubber in structural concrete and mortar.