Development of high performance and low-carbon red mud based lightweight concrete : a novel strategy for transforming red mud into sustainable concrete

Abstract

To facilitate large-scale red mud (RM) utilization in sustainable concrete and reduce industry dependence on cement and natural aggregates, this study developed a high-performance and low-carbon RM-based lightweight concrete (RM-LWC) by using RM based sulfur-aluminate cementitious material (RM-SAC) and RM based lightweight aggregates (RM-LWA). The effects of aggregates type (i.e. high-strength, lightweight and core-shell) on engineering properties of RM-LWC were investigated. The microstructure and micromechanical performance of the interfacial regions of RM-SAC paste and RM-LWA were revealed by elemental mapping and nanoindentation. The results demonstrate that substituting OPC with RM-SAC significantly enhanced mechanical properties and penetration resistance, while incorporating RM-LWA substantially reduced density and thermal conductivity of the concrete. Moreover, the internal curing effect provided by pre-wetting RM-LWA was more efficient in enhancing the performance of interface transition zone (ITZ) in concrete, compare to natural aggregates. The core-shell RM-LWA can further reduce the ITZ width and improve the micromechanics of ITZ in concrete. Based on RM-SAC and three types of RM-LWA, various RM-LWC with density of 1890–2100 kg/m3, compressive strength of 45.5–63.5 MPa, thermal conductivity of 0.47–1.13 W/(m·K) were obtained in this study. Furthermore, to evaluate the environmental and economic impact of the RM-LWC, the CO2 emission and cost of the RM-LWC, during the whole preparation process were calculated based on the actual production line. Compared to that of traditional concrete, the carbon emission and cost of the RM-LWC was reduced by 21.5 % and 20.1 %, respectively. Overall, this research may provide a novel strategy for transforming RM into sustainable concrete.