Development of composite cementitious material and optimization of slurry proportion based on fuzzy comprehensive evaluation

Abstract

In view of the high cost of cement cementing materials in mines, the low-cost cementitious materials were developed by using local solid waste resources, such as slag and fly ash; and the filling slurry ratio was optimized based on the existing filling system of the mines, so as to achieve maximum economic benefits on the premise of meeting the requirements of mines. Firstly, the physical and chemical analysis of the test material was carried out. Secondly, the orthogonal test and range analysis were used to optimize the proportion of composite cementitious material, and the optimized ratio was determined to be 10% fly ash(FA), 8% clinker, 14% desulfurization gypsum(DSG) and 68% ground granulated blast furnace slag (GGBFS). The hydration products and microstructure of composite cementitious material were explored by means of XRD and SEM, and its hydration mechanism was further revealed. Finally, based on this, the cementitious material was used to carry out the filling slurry ratio experiment, and the slurry ratio was optimized based on multi-objective fuzzy comprehensive evaluation method with 7 d strength, 28 d strength, bleeding rate(BR), slump and filling cost as indicators. The results show that, when the composite cementitious material is used, the ratio of tailings to Gobi aggregate is 1:1, the cement-sand ratio (CSR) is 1:6 and the mass concentration(MC) is 78% as the optimum proportion; and the verification test is carried out with this ratio, and the corresponding 7 d strength, 28 d strength, bleeding rate and slum pare 1.76 MPa, 4.82 MPa, 5.98% and 23.2 cm, respectively, which meet the requirements of the mine, and the filling cost is 103 yuan/m3, which is 47% lower than the original filling cost of 195 yuan/m3.