Rubberized geopolymer concrete: Dependence of mechanical properties and freeze-thaw resistance on replacement ratio of crumb rubber

Fly ash (FA), ground granulated blastfurnace slag (GGBS), and waste rubbers are solid wastes widely spreading around the world, which requires recycling for the environment protection. In this study, FA and GGBS were used as raw cementitious materials and crumb rubber (CR) was used as fine aggregate for preparing rubberized geopolymer concretes (RGC). The effects of replacement ratios of river sand by CR and ordinary Portland cement (OPC) by geopolymer on the mechanical properties and freeze-thaw resistance of RGC were investigated. The results show that compressive and tensile strengths slightly increased as the replacement ratio of CR increased from 0 to 10%, but decreased as the replacement ratio further increased to 20%. In addition, the incorporation of CR improved the stiffness and freeze-thaw resistance of geopolymer concretes regardless of the replacement ratio. For concrete containing 10% CR, it possessed a smaller size and fewer cracks produced inside the concrete than other concretes. In addition, CR has a good ability of energy dissipation, which can alleviate the damage resulted from the freeze-thaw cycle. However, the replacement of OPC by geopolymer played a detrimental role in the mechanical properties and freeze-thaw resistance of rubberized concretes. These results indicate that the addition of moderate CR favors the properties of geopolymer concretes and that the optimal replacement ratio is 10%, which ensures high strength and good freeze-thaw resistance.