| The research on coal gangue as the cement admixture has high economic value and social significance. At present, the utilization of coal gangue in this field is in extensive style, and has a lot of problem, such as the greater water requirement and lower strength, and the comprehensive utilization of the coal gangue was low. So the utilization of coal gangue in reasonable and effective is urgent affairs.This paper researched on the coal gangue as the cement admixture aiming at the problem on the utilization. The water requirement of spontaneous combusted gangue cement was decreased by changing the fineness and mixing amount of coal gangue; the relationship of water requirement and particle size distribution for coal gangue was studied; and the effect of grinding time of coal gangue on strength of spontaneous combusted gangue cement was researched; at last, strength of spontaneous combusted gangue cement was optimized by adding calcined dolomite, silica fume, slag. The main results were as follows:In this paper, the auxiliary gelling was modified by 750℃calcined dolomite, silica, slag and fly ash. The influence of SCG for admixture in cement on the water demand was studied, we can determined the optimum fineness and optimizational measures of SCG. The influence of different calcination temperature and soaking time on dolomite activity was studied by citric acid way and hydration way, we can find the best calcined system for dolomite. The supporting gel modification mechanism was studied by cement mortar strength, XRD, SEM. The main results were as follows:The influence of different grinding time for SCG on the water demand was studied. The experiment indicates that when the fineness of SCG increased, the water requirement decreased. When the fineness of SCG increased more, the water requirement of cementitious system will trend to increase significantly.The influence of particle size distribution of SCG on the water demand of cement system by gray relational analysis was studied. The results showed that no matter the fineness of cement, the particle size of SCG ranging from 5.0μm to 10μm will increase the water demand of cement system, and it will help reduce the water demand of cement system when the particle size of SCG appropriated to increase the range of 10～40μm.When compounding slag and steel slag into coal gangue respectively, the water requirement of steel slag gangue cement system was higher than slag gangue cement, but all were lower than only having coal gangue.The influence of calcining technology on the activity of light- burned dolomite was studied. The experimental results showed that the best technological parameters of calcining process were as follows:calcinations temperature was 750℃, holding time was 2.5h.Compound doped with 750℃calcined dolomite to modify the SCG for mixed materials by means of cement mortar test was studied. The experimental results showed that calcined dolomite contributed to increase the early strength of cement systems, but post- strength was all lower than the only doped SCGThrough the introduction of silica fume, each group has different levels to increase strength, early strength was not significantly increased when compared with only doped SCG. When calcined dolomite content of 8 wt%, the 28- day strength was 8 MPa bigger than the strength of uni doped SCG, and the 90- day strength was 11 MPa bigger than the strength of uni doped SCG.For spontaneous combustion gangue, the compound effect of slag was equal than fly ash, and the strength of cement system will increase with the content of slag and fly ash increased. When content of the slag is 10 wt%, the 28- day strength was 10 MPa bigger than the strength of uni doped SCG,60- day and 90- day on average was nearly 7 MPa. When the content of fly ash is 10 wt%, the 28- day strength was 7 MPa bigger than the strength of uni doped SCG,60- day and 90- day on average was only 3.5 MPa.
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