Microstructure, thermal conductivity and carbonation resistance properties of sustainable structural lightweight concrete incorporating 100% coarser rubber particles

An all-encompassing effort has been performed to utilize waste tire rubber particles for replacing binders and conventional aggregates in concrete, and very little work has been found in the current literature on structural lightweight concrete (SLWC) for the complete replacement of traditional aggregates by waste tire rubber. Notably, there is no available study addressing the microstructure, thermal performance, and carbonation resistance of SLWC with 100 % waste coarser rubber content. Therefore, this study investigated the thermal conductivity, carbonation, X-ray CT scan, and extensive microstructural properties of novel structural lightweight concrete (SLWC) with 100 % waste rubber to substitute conventional aggregate for the first time. Different variables, such as large and smaller rubber particles, normal and compressed samples, and steel fibers, were introduced. Maximum compressive strength of 18 MPa with a density of 2115 kg/m3 satisfied the prerequisite for SLWC prescribed by ACI 213R. Non-destructive tests, including electrical resistivity and ultra-pulse velocity tests, were conducted to identify the soundness of concrete. The microstructural properties, i.e., energy dispersive spectroscopy, scanning electron microscopy, and X-ray CT scan, were evaluated to demonstrate the effectiveness of the novel casting method. The thermal conductivity of 0.29 W/m.k indicated excellent thermal insulation performance of SLWC, denoted by ASTM C332. Carbonation resistance was also considerably improved. The results show that the SLWC in this study has excellent potential for both structural and non-structural applications.