| Portland cement is traditionally used as binder for cemented paste backfill, which makes the mining cost high, the filling mining used in underground mine becomes the fatal technology problem. The blast furnace slag (BFS) is a kind of industrial waste which is produced in blast furnace process, and it not only contains the potential pozzuolana activity but also has high production. Using BFS as the main raw material in mine filling system, which has important strategic significance to save production resources and energy and protect environment.This paper takes BFS as the raw material, through mixing into different content of cement clinker, gypsum and activator in the slag material make up binders. The different types of slag cementitious materials are used to solidify the different type of tailings in order to ascertain the mixture ratio. According to the rule of filling body strength and capability, the paper discussed cementing mechanism of slag cementitious material in mine backfilling, which will provide theory evidence and technical support for further application of the slag cementitious materials in paste backfill.(1) The experimental results indicated that the different types of tailings have some selectivity for slag cementitious material. The mechanical strength results have shown that using H1 material has the best solidification effect relative to CHENCHAO tailings, and the H4 has better performance for JINSHANDIAN tailings than other types of slag cementitious material.(2) By unconfined compression strength (UCS) tests of filling body with slag cementitious material, influencing rules of binder addition ratio, mortar density and curing time on the strength are individually analyzed. The UCS of tailing added 5.3% slag cementitious material are higher than the tailings added 10% cement after curing 28 days. There are many other factors influence on the strength of filling body, for example, the content of flocculating agent and fine waste rock, experimental water, curing condition.(3) Based on the analysis of micro-damage mechanism and damage performance of the whole tailings and the waste rock-tailings filling body, two different damage constitutive model are established under unconfined compression condition.(4) Using XRD, SEM, TG-DSC et al tests to observe and analysis the hydration products of slag cementitious material and component and microcosmic frame of filling body. It is found that the main hydration products of slag cementitious material are calcium silicate hydrate (C-S-H) gel and ettringite (AFt) crystal. The presence of hydration products is a good indication that cementitious bonds are forming and therefore the strength of material is increased. The active components of tailings are mica clay minerals and carbonate minerals, which take part in hydrate reaction in order to improve filling body’s performance.(5) According to the characteristic of slag cementitious material and tailings system hydrating process, the paper establishes a physical model of slag cementitous material hydrating reaction by using SEM analysis. The hydrate reaction of slag cementitious material can be considered as multiply-reaction of mineral through physical model. The potential hydraulicity of slag is activated by alkali and sulphate, which reflects favorable cementing capability.(6) The tests of paste backfill in mine industry indicate:slag cementitious material can instead of cement as a binder in backfill system, and the filling body is more advantageous to the development of its intensity in the moist environment in well. |
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