Experimental Study On Preparation Of High Belite Sulphoaluminate Cement From Coal Gangue

Coal gangue is a solid waste with the biggest discharge.When it is used in cement production,it not only reduces the consumption of natural raw materials by using solid waste,but also has significant effect on energy saving and carbon reduction.In this paper,high belite sulfoaluminate cement（HBSAC）was prepared from coal gangue.The clinker sintering process,reaction mechanism,calcination system,clinker mineral composition and cement mechanical properties,hydration properties of cement slurry and the product microstructure were studied by XRD,FTIR,TG-DSC and SEM.The main results are as follows:（1）The optimum calcination condition for preparing HBSAC clinker from coal gangue is to hold at 1300℃～1350℃for 60 min～90 min.Through optimization theory and experiment,when HBSAC clinker mineral composition of 51%β-C₂S,36%C₄A₃（?）and 10%C₄AF.The cement has good physical properties and the proportion of coal gangue is up to 27%.（2）There are two heat release peaks in the hydration of HBSAC prepared from coal gangue,both of which appear before 16 h with rapid exothermic heat.The hydration products were mainly needle-rod AFt,flocculent or network C-S-H gel,petal-like AFm,hexagonal flake CH crystal and C₂ASH₈.The 3-day and 28-day compressive strength of the cement prepared with pure HBSAC clinker were 30.5 MPa and 35.2MPa,respectively.（3）In the preparation of HBSAC clinker-gypsum system from coal gangue,gypsum retards the setting time of cement.When gypsum content is 11%,the 28-day compressive strength of cement reaches 47.8MPa.In the HBSAC clinker-gypsum-limestone composite cement system,limestone plays a certain role in retarding coagulation.The addition of limestone is effective in improving the strength of cement in the later stage,but too much will reduce the strength of cement in the early stage.When the mass percentage of HBSAC clinker-gypsum-limestone is 89:6:5,the setting time of cement meets the construction requirements,and the 28-day compressive strength reaches 54.2MPa.The results of this paper provide a theoretical and practical basis for the technical development and application of HBSAC prepared from coal gangue.