Study On Preparation Of New Type Gypsum Block With Desulphurization Gypsum

Desulfurization gypsum as one of the largest power plant emissions of solid waste,preparation of new type gypsum block by using desulphurization gypsum has important significance to realize the resource utilization and environmental protection. In this paper,prepared the desulfurization building gypsum by appropriate heat treatment system to meet the requirements, with fly ash and cement clinker complex preparation of composite cementitious material, and the desulfurization gypsum building block meet the gypsum block "(JC / T698-2010) requirements specification was preparated by adding expanded perlite, glass fiber and water proofing agent. Determining the optimum matching of the desulfurization gypsum,fly ash and cement ratio by orthogonal test, adding citric acid and water reducing agent and other additives to improve the physical properties of cementitious materials, the mechanical strength of cementitious materials was improved by using quick lime, calcined gypsum and chloride salt as modified materials, and the hydration process and hydration mechanism of FGD gypsum-fly ash-cement cementitious system and FGD gypsum-slag-cement system were studied. The paper focuses on the analysis of the effects of additives, modified materials content and curing conditions on the mechanical properties of cementitious materials, through the experimental study on the effect of expanded perlite, glass fiber and waterproofing agent on the properties of the block, in order to get the best formula of block and the theoretical basis for the production and promotion of the desulfurization gypsum block is provided. The main conclusions are as follows:(1) The optimum heat treatment condition of FGD building gypsum is 150 ?, thermal insulation 2h, flexural strength and compressive strength are 3.6MPa and 9.2MPa respectively,the initial setting time and final setting time are 13 min and 27 min, the performance in line with the "building gypsum"(GB9776-2008) specifications.(2) The devulcanized building gypsum as the main raw material, fly ash and cement clinker is mixed with the active material, by the method of orthogonal test obtained optimum mix ratio of FGD gypsum, fly ash and cement clinker is 55%:20%:25%. The effects of the content of the modified materials such as retarder, water reducing agent, lime, calcined gypsum and chlorine salt on the physical properties and mechanical properties of the cementitious materials were studied, the best content is 0.02%, 0.3%, 10%, 10%~15% and1.5%, Slag powder instead of fly ash can effectively improve cementitious materials mechanical properties, the desulfurization gypsum, slag, cement ratio is 55%:25%:20%,cementitious materials mechanics performance best, 7d and 28 d compressive strength respectively for 22.5MPa and 32.9MPa.(3) Through the different curing conditions analysis the influence of curing process and curing temperature on the mechanical properties of cementitious materials, natural curing conditions of cementitious materials mechanics performance best, 7d and 28 d compressive strength reached 17.4MPa and 28.5MPa, the best curing temperature is 30?to 40?.(4) The hydration process and hydration mechanism of FGD gypsum-fly ash-cement cementitious system and FGD gypsum-slag-cement cementitious system are analysized by micro measurements, which offer theoretical basis for the comprehensive utilization of FGD gypsum and fly ash and slag.(5) The effect of the experimental parameters, including expanged perlite, glass fiber and waterproofing agent, are investigated for the physical and mechanical properties of block using FGD gypsum-fly ash-cement as the cementing materials. The optimum formula of desulfurization gypsum block is determined for cementitious materials 1000 copies, 125 portions of perlite, 14 copies of glass fiber, waterproof agent dosage is 2%. The apparent density of P type block is 953kg/m3, the breaking load is 2730 N, the compressive strength is10.6MPa, the apparent density of F type moisture block is 959kg/m3, the breaking load is2700 N, the compressive strength is 10.5MPa, the softening coefficient is 0.82.