Experimental study of microwave heating on mechanical properties of fly ash-based cementitious materials

The mechanical properties of fly ash-based cementitious materials significantly impact the quality of backfilling in coal mine goafs. This paper first conducts experiments on the material proportion of fly ash-based cementitious materials to study the influence characteristics of water-cement ratio and fly ash activator on the mechanical properties of fly ash-based cementitious materials. Based on this, microwave heating experiments are conducted to study the effect characteristics of different microwave heating conditions on the mechanical properties of cementitious materials. When the activator content is 10 g and the mass ratio of ash and cement is 6: 4, the strength of the cementitious material reaches 9.21 MPa after curing for 7 days, which meets the requirements of coal mine filling. When the microwave power is 3 kW and the heating time is 3min, the uniaxial compressive strength is the highest. The increase rate of the strength with the microwave heating power of 3 kW and the heating time of 3min is the largest. The increase rate of the strength of the cementing material with the curing time of 1 d, 3 d and 7 d is 43.13%, 47.68% and 38.44%, respectively. A reasonable microwave heating path is beneficial to increase the strength of cementitious material. The unreasonable microwave heating paths will expand the internal structure of cementitious materials and reduce the strength. The research content of this paper can provide help for microwave heating technology in coal mine backfill application of fly ash-based cementing material and has essential significance for coal mine environmental protection.