Impacts of slag-based-binder fineness on strength in mining backfill

Abstract

For the slag-gypsum binder (SGB) applied in mining backfill, which the quantity percentage of slag could be exceed 75%, this research studied the influencing rules of the SGB fineness on backfilling body strength. Firstly, tests on different milling duration of the SGB were carried out to study the SGB particle characteristics. It shows that surface area measurement is significantly affected by temperature, therefore, a new index δ which indicates cumulative particle percentage larger than 45 μm was used to evaluate the SGB fineness. And the best milling duration is 0.5 h, overtime milling contributes to a low efficiency drastically. Secondly, it carried out strength tests on the backfilling body with different SGB fineness δ , established an exponential function between strength and water-cement ratio. To illustrate the result of “the finer SGB, the higher strength”, a concept of relative activity index (RAI) η was presented, and the result shows that δ and η forms an inverse log-linear relationship. Finally, a modified strength predicting model which considers the impact of slurry concentration, cement ratio and SGB fineness was established, and the verification tests show that the predicting error is below 10%, which is completely within the industrial adaptation.