The Formulation Of The Fgd Plastering Gypsum And The Study Of Its Performance

Setting time of flue-gas desulfurization(FGD) building gypsum plaster is very short, usually only 5～20 min,and operation time is too short,which cannot satisfy the practical plastering and construction of gypsum-based material.There are some reasearch for the performance of hydration and hardening on FGD building gypsum itself, in order to improve the workability,water retention, adhesion and climate resistant,some systemic investigations have been carried out on the preparation mechanism and method of FGD plastering gypsum,action mechanism of various additives, formula and related properties of underlying plaster,surface layer of plaster, aiming to promote the development of high performance FGD plastering gypsum.A variety of retarders,HPMC,waterproofing agent,adhesive agents were added to the FGD building gypsum respectively and tested for some relevant performance; For example, by testing the setting time, flexural strength, compressive strength, supersaturation of liquid phase, hydration rate, hydration temperature, crystal morphology of gypsum with the retarders; The Scanning Electron Micrographs of gypsum and gypsum with the retarders also make us known the influence of retarders on the crystal morphology,from which transformation of microstructure induced by retarders and the reason of which makes the strength drop are analyzed;Testing the setting time, flexural strength,compressive strength, water retention, adhesive strength of gypsum with the HPMC; Testing the setting time,flexural strength, compressive strength, absorption rate, softening coefficient of gypsum with the waterproofing agent; Testing the setting time, flexural strength, compressive strength,water retention, adhesive strength of gypsum with the adhesive agents.Through the analyzing the relevant phenomenon performance of that mixing the additives above on the gypsum respectively,the author initially identify the variety and content of additives which need to add on the preparation of plastering gypsum.Citric acid is the high-efficiency retarders of FGD gypsum.Reference standard of plastering gypsum, which extend the setting time, flexural strength, compressive strength decreased relatively slow,and the minimum volume shrinkage.Generally,the suitable dosage of FGD gypsum is 0.3～0.5%. MK(200000) is the high-efficiency water- retentive agents of FGD gypsum,which increases the water retention, workability, consistency.Generally, the suitable dosage of FGD gypsum is about 0.1%. Addition of redispersible latex powder is the efficient way to increase the adhesive strength of FGD gypsum, among various polymer adhesive agents,the integrative modification effect of 5044 is the best.5044 can increase the workability,adhesive strength of FGD gypsum significantly. Generally, the suitable dosage of FGD gypsum is 0.1%～0.25%.By modification with retarders, HPMC and adhesive agents, FGD plastering gypsum can be prepared with good workability,adhesive capacity and climate resistant.Adding admixtures in the gypsum that can adjust the performance of FGD building gypsum: Adding the sand and fly ash that could adjust the performance of the underlying plaster and achieve the purpose of reducing costs;Adding talcum powder and (or) ash calcium powder in surface layer of plaster that could improve its performance, such as workability,the degree of smooth, the friction and so on.Through the test of macroscopic performance of the hardened plaster surface which have different fineness,summing up the regularity that the fineness influence surface layer of plaster.Based on the requirements of performance and characteristics of construction between the underlying plaster and the surface layer of plaster,the author determine the formula of the underlying plaster and the surface layer of plaster on the reasonable cost,and plastering gypsum based of the FGD gypsum is prepared.