Abstract: Using blast furnace slag and fly ash from a material company in Henan as raw materials，NaOH solution as alkali activator，the strength test of cement filling body for the metal mine tailings in Shandong is conducted.The results showed that when blast furnace slag/fly ash mass ratio was 4，NaOH concentration was 8 mol/L and liquid/solid mass ratio was 0.5，the 3 d and 28 d compressive strength of cement filling material was 2.12 and 6.84 MPa respectively，which meets the requirements of backfilling.SEM analysis shows that a large number of gel phase is generated after alkali activation，which is the main reason for improving strength of the filling materials.XRD and FTIR analysis showed that the crystal phase peaks of hydrated calcium silicate appeared in the Alkali activated material.［SiO₄］ is reconstituted after the depolymerization of Si（Al）—O—Si under the activation of alkali solution and furthermore，carbonate minerals were formed in Alkali activated material through the adsorption of CO2 from atmosphere.All these were the sources of strength of the test specimens.

Key words: Blast furnace slag, Fly ash, Alkali activation, Cement material, Backfilling, Compressive strength