Abstract:In this paper, the basic chemical properties of mining and metallurgical waste slag and raw materials are measured, and compound strong alkaline activator is developed according to the test results, which can be used to activate the activity of mining and metallurgical waste slag, so as to prepare special backfill cementitious material. The hydration reaction products in the backfill were tested by XRD. The results showed that the main hydration products supporting the strength of backfill were ettringite (AFt), calcium hydroxide (CH), aluminum glue (AH_8-10), calcium silicate hydrate (C-S-H), hydrated calcium aluminosilicate (C-A-S-H), etc. The formation of one ettringite (AFt) molecule will bind and adsorb 32 H₂O molecules, indicating that the special backfill cementitious material is more suitable for backfill slurry with larger water content. At the same time, SEM was used to analyze the internal structure of the backfill at different ages, revealing the strength growth law of the backfill, and analyzing the strength mechanism of the backfill at each stage. The strength of backfill of two kinds of cementitious materials was tested by strength test under different conditions. The results showed that the strength of backfill prepared by special cementitious materials (KS) was higher than that prepared by cement (SN), and the strength was 1 times different.