Development of cemented paste backfill based on the addition of three mineral additions using the mixture design modeling approach

Abstract

Large-scale mining operations have produced large amounts of iron ore tailings (IOT) and stopes. IOT will cause air and water pollution, and open stopes may lead to surface subsidence or even geological disasters. Using cemented paste backfill (CPB) which is composed of IOT and binders to fill stopes can well solve the above two problems. Based on the alkali-activated theory, slag and desulfurized gypsum are selected as basic materials, cement (C), lime (L) and silica fume (SF) are chosen as mineral activators. Mixture design, an experimental design method, is used to model the effect of C, L, and SF on the spread, compressive strength and shrinkage ratio of CPB. The models are helpful to know the interaction between three mineral additions. Results show that the optimal spread is reached when the content of C and SF are 8% and 5%, respectively in C-SF binary system. The compressive strength at 3,7,28 days increase and then decrease with the increase of each admixture in L-SF and C-SF binary system. The maximum compressive strength at 28 days is 0.83 MPa, which can provide support for the adjacent mine structure and keep a stable working platform for miners. The shrinkage ratio decreases with the increase of SF content and increases with the increase of C content in C-SF binary system. However, in C-L binary system, the shrinkage ratio increases with the increase of L or C content. The minimum shrinkage ratio is 1.16% (corresponding to the proportion of 7% of C, 3% of L and 5% of SF). Finally, the morphology of hydration products at different ages are compared by scanning electron microscopy (SEM). The results show that the derived models are very effective in explaining the influence of three mineral admixtures on the workability and mechanical property of CPB. This design method is a useful tool to select the optimal mix proportions to achieve engineering objectives and reduce cost.