Sustainable use of red mud in ultra-high performance concrete (UHPC): Design and performance evaluation

This paper presents an efficient application for red mud, i.e., recycling red mud as a mineral additive in the development of ultra-high performance concrete (UHPC). Specifically, the modified Andreasen & Andersen particle packing model has been carried out to obtain a densely compacted UHPC matrix. After that, red mud is used to replace cement to reduce both the landfilling of red mud and the environmental burden of UHPC. Then, the fresh and hardened behavior of UHPC with and without red mud has been evaluated. It has been found that the addition of red mud enhanced early-age (7 d) durability due to the accelerated hydration process, while reduced the workability and the mechanical properties of UHPC. The degraded workability may affect the application in the building with complex shapes, but it can still be applied in general construction. An ultra-high strength (>150 MPa) of UHPC including 40% red mud can be generated after high-temperature curing, although the addition of red mud reduces the compressive strength. Besides, it is noteworthy that significantly shortened setting time can be obtained when replacing cement by red mud, providing ideas for the application in the UHPC rapid-repairing process. The pore structure analysis reveals a coarsening of micro-pore structure with an increase of red mud content. Finally, a low-energy consumption, as well as low radiation risk further promotes the environmental protection application of red mud based UHPC.