Effect of microwave on coupled rheological and mechanical properties of cemented tailings backfill

Cement tailings backfill (CTB) is a mixture of tailings, binders and water that is widely utilized to fill underground mining areas. Once placed, the CTB needs to provide adequate ground support as soon as possible to improve mining efficiency. Microwave heating can accelerate the curing process of CTB, thereby improving the mechanical performance of CTB. However, if the CTB slurry is under the heating condition, the early hydration reaction process of the mixture can be accelerated, consuming more water in the CTB materials and thus resulting in reduced fluidity. Therefore, this study proposes an experimental scheme to incorporate microwave heating into the preparing and curing of CTB, so as to realize the improvement of the mechanical strength of CTB body under the condition of also ensuring the fluidity of fresh CTB. The results indicate that with the appropriate microwave heating time (2–4 min) and power (600 W) applied, both the flowing ability and strength in the plastic and hardened CTB can be improved. The improvement in fluidity of CTB is ascribed to the intensification of molecular thermal movement, while the enhancement in strength of CTB is due to the acceleration of binder hydration progress. The current study can also contribute to further practical application of microwave heating in the preparation process of CTB before it is placed into underground mined-out areas.