Abstract: Environmental pollution caused by industrial solid waste is a major obstacle to cleaner production. In order to achieve sustainable development,magnesium slag ( MS) and fly ash ( FA) are recovered as cementing materials,and then mixed with tailings (TL) to make a paste filling material that can be used in mining engineering. The rheological properties, mechanical properties and pore structure evolution of backfill with different fly ash content and tailings content were studied. In this process,the following conclusions are obtained:① With the increase of fly ash content,the mini-slump value first increases and then decreases. When the fly ash content is 20%,the fluidity of backfill is the best. ② Uniaxial compressive strength increases with the increase of curing age and fly ash content,and decreases with the increase of tailings content. Backfill with low fly ash content develops slowly in the early strength, while backfill with high fly ash content develops rapidly in the early strength. ③ The critical pore size and porosity decrease with the increase of fly ash content. The greater the fly ash content is,the greater the critical pore size decreases. With the increase of tailing content,the critical pore size and porosity increase gradually.

Key words: modified magnesium slag,backfill,slump,compressive strength,pore structure