Experimental study on the performance of goaf filling materials with high content of fly ash

Abstract

In this paper, fly ash is studied as the main cementing material for coal mine goaf filling. The performance of the filling materials with 90% fly ash such as compressive strength, impermeability, viscosity, additive effect and diffusion rule are studied experimentally and theoretically. The results show that compressive strength and impermeability are positively correlated with cement content when water-solid ratio is 0.7:1.0 with 90% fly ash. The compressive strength increases slowly in the early stage while it increases with a faster speed in the later stage. The compressive strength of the material after 60 days of curing is 1.90 times that of 28 days. Additive could promote the activity of fly ash and improve hydration reaction. The interparticle porosity is reduced, but strength at early stage and impermeability are increased. The viscosity of the filling material has an obvious shear thinning phenomenon as shear rate increases. An inflection point appears when shear rate is 30s−1. The filling material with high content of fly ash presents the rule of horizontal diffusion and longitudinal accumulation in goaf filling treatment. The diffusion distance and accumulation height are positively correlated with grouting pressure.