Research On Fluorine Gypsum Modification And New-style Building Materials

Fluorine gypsum is a kind of industrial waste made from fluorine industry, its dischargeincreases year by year, but comprehensive utilization rate is low, large amounts of fluorinegypsum is scrapped, occupying much land and polluting surrounding environment. Fluorinegypsum is one of anhydrite resources and has potential hydration activity without beingcalcined, the modified fluorine gypsum can be used as cement material. In allusion to theproblems above, this paper studies fourgypsum optimization modification methods andapplication in new-style building materials, in order to realize flourgpsum comprehensiveutilization.Properties of fluorine gypsum are characterized by X-ray diffraction analysis, scanningelectron microscope, chemical analysis, particle size and so on. Results indicate that fluorinegypsum main phase composition is CaSO4, the content of CaO and SO3in fluorine gypsum ismore than97%, fluorine gypsum is made up of granular crystal, crystal regularity andcrystallinity are high, particles size is from0.2um to200um, and fluorine gypsum is a kind ofgypsum resources, owning high purity, wide particle size distribution and potential hydrationactivity.In the experiment of fluorine gypsum physical modification, effects of different grindingtime and calcination temperature on fluorine gypsum properties are studied, and the mechanismis discussed. Results indicate that grinding processing can improve fluorine gypsum particlesize distribution, decrease water demand for normal consistency, reduce fluorine gypsumsetting time, and enhance hardened paste strength, the optimum grinding time is20min;calcination treatment can not improve fluorgpysum properties obviously, its function is little.In the experiment of fluorine gypsum chemical modification, effects of different kinds ofadditives on fluorine gypsum setting time、strength and efflorescence degree are studied.Results indicate that single kind of additive funcation is not comprehensive. Small amount ofadditive A can shorten fluorine gypsum setting time obviously, enhance fluorine gypsum earlystrength, and cause fluorine gypsum efflorescence; the addition of sodium carbonate canpromote fluorine gypsum hydration, energize strength, but the needed mount of sodiumcarbonate added in fluorine gypsum is high, and the effect of sodium carbonate is small; large amount of additive B can accelerate the process of fluorine gypsum hydration, enhancelong-term strength, and avoid fluorine gypsum efflorescence, but the effect of alums on fluorinegypsum is limited; the addition of sodium nitrite can shorten fluorine gypsum setting time, butcause the defect of expansion, crack and warping, volume stability of fluorine gypsum is poor.In the experiment of fluorine gypsum composite modification, effects of different kinds ofadditive on fluorine gypsum properties are studied, and the optimum method of fluorinegypsum modification is developed. Results indicate that the addition of additive B can restrainefflorescence of fluorine gypsum/additive A composite cementitious material, and the additionof dihydrate gypsum can shorten the setting time of fluorine gypsum/additive A/additive Bcomposite cementitious material in further. The optimum method of fluorine gypsummodification is listed as follows: fluorine gypsum grinding time is20min, the dosages ofadditive A is1.0%, additive B is0.7%, dihydrate gypsum is1.5%, the initial setting time ofcomposite modification fluorine gypsum is4.4h, final setting time is5.5h,7d’s flexural strengthis7.6MPa,7d’s compressive strength is39MPa, properties of composite modification fluorinegypsum satisfy the demand of fluorine gypsum utilization in building materials.In the experiment of fluorine gypsum-based self-leveling materials, the compatibility offluorine gypsum with different kinds of superplasticizer is tested, the effect of re-dispersibleemulsoid powder on fluorine gypsum-based self-leveling material mechanical property isstudied, and its mechanism is discussed. Results indicate that the compatibility of fluorinegypsum with naphthalene superplasticizer is better, re-dispersible emulsoid powder canimprove fluorine gypsum-based self-leveling material mechanical property, and the optimumdosage of naphthalene superplasticizer is1.0%, re-dispersible emulsoid powder is3%.In the experiment of fluorine gypsum-based foam materials, effects of foaming agent,foam stabilizer, polypropylene fiber and waterproofing agent on properties of fluorinegypsum-based foam materials are studied, and the mechanism is dicussed. Results indicate thatthe optimum dosage of foaming agent is5%, foam stabilizer is1.5%, polypropylene fiber is0.5%, and waterproofing agent is2.0%.