Effect of rubberized concrete integrating uncoated and coated crumb rubber on the flexural behavior of the RC beams reinforced with steel and GFRP bars

In this investigation, crumb rubber (CR) was a viable substitute for concrete's conventional natural fine aggregate (FNA). This approach carries dual advantages: the conservation of natural resources and the environmentally conscious recycling of rubber waste, diverting it from traditional disposal methods. The study incorporated varying proportions of CR (5%, 10%, and 20%) by volume of the sand used in the mixtures. The primary study objective is to enhance the bond between CR particles and the surrounding concrete components by coating the CR with cement or fly ash slurry (CTR and FATR). For the limitation of the previous research discussed the CR effect on the beam’s behavior, fourteen beams were poured with different rubberized concrete (RuC) and tested in flexure. This comprehensive approach sought to assess the influence of diverse factors, including rubber content, treatment materials, and the nature of internal reinforcement, on the overall performance and characteristics of the beams. The results assumed that the compressive strength was raised by 6.0–11.0% and 13.0–22.0% for the mixes cast with CTR and FATR, respectively, compared to the corresponding mixes cast with UR. Consequently, the tensile strength of the RuC-integrated CTR and FATR was raised by 5.9–11.0% and 14.0–22.0%, respectively, compared to the mixes integrating uncoating CR. Moreover, the beams cast with FATR concrete experienced the highest flexural capacities among all the steel RC beams. Furthermore, using the carbon fiber reinforced polymer (CFRP) bars as internal reinforcement for the RC beams showed the highest load capacities. •The coated and uncoated crumb rubber wastes were a viable substitute for the fine aggregate.•The compressive strength was raised by 6.0–11.0% for the CTR mixes.•The compressive strength was raised by 13.0–22.0% for the FATR mixes.•The beams cast with FATR concrete experienced the highest flexural capacities.