Mechanical properties and micro characterization of coal slime water-based cementitious material-gangue filling: A novel method for co-treatment of mining waste

Abstract

With the improvement of coal mining depth and mechanization level, the difficulty of coal slime water (CSW) disposal increases. The preparation of cementitious materials with CSW can not only solve the disposal problems, but improve the structural stability and mechanical properties of coal gangue (CG) piles as a cementitious material. At the same time, it realizes the cooperative resource utilization of mining waste and reduces environmental pollution. In this study, it is proposed to prepare high water contained coal slime water-based cementitious material (CSCA) with 6 types of additives to bond CG particles and improve mechanical properties. Study on property of compressive strength CSCA-CG (CGSB) show that five factors (f1-f5) influence the property order as: calcination temperature of CG (f5) > CG particle size distribution (f4) > ratio of CG and CSCA (f1) > additives content (f2) > volume of water glass (f3). The optimal experimental parameters were that f5 calcined at 800 °C for 30 min, f4 with 0 ∼ 0.18 mm (6 %), 0.18 ∼ 2 mm (24 %) and 2 ∼ 5 mm (70 %), f1 of 4:1, f2 of 5 %, and f3 with 3 ml. The mechanical experiments shows that the uniaxial compressive strength of aged 28 d could reach 1.48 MPa, and results of variable angle shear test at 50°showed that principal stress of 1.26 MPa and shear strength of 1.45 MPa were obtained. The CGSB prepared with by non-calcined CG has better plastic deformation ability and less strength loss after peaking. The reason for improved uniaxial compressive mechanical properties of CGSB with calcined CG are suggested as following: densifying the structure of CG, strengthening the hydration process of cementitious materials, and promoting the growth of calcium alumina structure. Therefore, it is suggested that this study provides new ideas for CSW-CG co-disposal and provides a reference solution for mechanical property optimization.