Abstract: A new type of backfill material with self-leveling and self-compacting properties was prepared with excavated silt, cement and water as raw materials to effectively solve the problem of insufficient compaction of traditional fillers in backfilling projects. The red mud produced by the alumina industry was incorporated into the backfill material to replace part of the cement, with the purpose of improving the utilization of industrial waste and further reducing construction cost. With flowability as the control index in mix proportion design, the mixture with a water-solid ratio of 0.43 could meet the flowability requirement (200-300 mm). Furthermore, the flowability, bleeding and compressive strength of the mixture were examined respectively via indoor test. Results demonstrated that the increase of red mud could reduce the flowability and bleeding rate of the mixture, and meanwhile accelerate the bleeding. The partial replacement of cement by red mud does not affect the growth rate of the mixture’s strength. The strength of the mixture increases when red mud content is in the range of 10%-15%, while declines when red mud content is smaller than 10% or greater than 15%. Red mud has a good application prospect in terms of bleeding stability and strength for flowable silt backfill materials.

Key words: flowable backfill materials, industrial solid waste, red mud, silt, performance, bleeding rate