Effect of multifunctional modification of waste rubber powder on the workability and mechanical behavior of cement-based materials

In this study, a new modification method of waste rubber powder (WRP) was proposed to improve the workability and mechanical properties of rubber cement-based materials (RCM). This method combines mechanochemical action, inorganic powder intercalation, and modified slurry coating to obtain modified rubber aggregates (MRA). The modification mechanism and structure properties of the WRP were measured and characterized by NMR and TG-DSC. The effects of the WRP and MRA on the hydration, workability and mechanical behavior of RCM were further studied by an isothermal calorimeter, and rheometer. The ITZ between rubber and the cement matrix (R-CM) was analysed by SEM, Micro-hardness. The result showed that the porosity of the MRA was reduced (24.68 to 17.87) and the stability is increased (mass loss rate was reduced from 64.8 % to 57.5 %) compared with the WRP. WRP delayed the hydration induction and acceleration periods of cement hydration by 9 h, but MRA was only 0.5 h compared with control groups. The yield stress and plastic viscosity of MCRM were decreased by 356.95 % and 154.65 % respectively, compared with CRM. The compressive and flexural strengths of MCRM increased by 159.0 % and 87.5 % compared with CRM. The voids at the interface of R-CM disappeared after modification, and ITZ thickness decreased from about 160 mu m to 80 mu m. The interfacial adhesion of R-CM is a key factor in improving the failure model and mechanical behavior of RCM.