Influence of waste tire rubber powder, polypropylene fiber and their binary blends on mitigating alkali-silica reaction

Abstract

This work aims to investigate the inhibitory effect and inhibitory mechanism of waste tire rubber powder (abbreviated as WRP) and polypropylene fiber (PPF), and their binary blends on mitigating the alkali-silica reaction (ASR). To achieve this, mortar bars containing either WRP, PPF, or WRP + PPF were prepared for the accelerated mortar bar test (AMBT). The mechanism of ASR inhibition was illustrated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray computed micro-tomography (X-ray CT). The results indicated that the combination of WRP and PPF showed excellent synergistic effect on improving the compressive strength of the mortar cubes. In addition, WRP could effectively alleviate ASR, but the effect depended on the particle size of WRP, with the inhibition effect of 120 mesh WRP being the best. The addition of WRP + PPF exhibited an excellent synergistic effect on the inhibition of ASR expansion, and 120 mesh WRP and PPF with a length of 9 mm and a dosage of 0.8 kg/mm3 showed the best inhibition effect when they were incorporated together. Moreover, the inhibition mechanism of WRP and PPF on ASR was physical effect: WRP consumed the swelling energy generated by water absorption of the gel through deformation, and PPF applied its own bridging effect to suppress crack propagation. Finally, the analysis of the X-ray CT scanning results showed that adding WRP and PPF to the slurry increased the porosity. With the progress of ASR, the gel filled the pores and decreased the expansion. This further revealed more about how WRP and PPF could work together to reduce the damage caused by ASR effectively.