Effect of Fly Ash on the Mechanical Properties of Cemented Backfill Made with Brine

Sanshandao Xinli Gold Mine in Shandong Province is the first Chinese subsea gold mine. The mine uses cement backfill in the open stopes. The existence of a high concentration of Cl− in the water use to create the cement backfill affects its strength. An analysis by scanning electron microscopy and x-ray diffraction investigated the effect of salt brine on mechanical properties of cement backfill and micro-corrosion mechanism, the suitable mineral admixture of fly ash was selected after conducting theoretical analysis to decrease the effects of brine. A relationship between the elastic modulus and the uniaxial compressive strength of the cemented backfill was determined. The density, cohesion and internal friction angle of the cemented backfill were obtained. Based on x-ray diffraction analysis of fly ash, scanning electron microscope test and testing the addition of fly ash in varying amounts and ways of introduction, the mechanism for improving the uniaxial compressive strength of the cement backfill produced with the fly ash and the best mixing quantity of the fly ash was determined in briny conditions through experiments and theoretical research. Rheological properties of the filling slurry with fly ash were also investigated.