Research On Improving The Properties Of Desulfurization Gypsum Cementing Materials

Desulfurization gypsum is the by-product gypsum of the wet flue gasdesulphurization process of coal burning boiler in the power plant and has become thesecond largest solid waste after the fly ash. Preparation of building materials usingdesulfurization gypsum is one of the important ways of high added value utilization ofdesulfurization gypsum. For the problem of poor water resistance and low strength ofdesulfurization gypsum, the inorganic reinforced materials of sulphoaluminate cementclinker and ground granulated blast furnace slag and chemical admixtures such as H2O2,naphthalene water reducing agent, sodium carboxymethyl cellulose and organosiliconwaterproofing agent were added to control and optimize the composition and structure ofdesulfurization gypsum material.The strength and water resistance of the desulfurization building gypsum can besignificantly improved by doping sulphoaluminate cement clinker. The flexural andcompressive strength cured for7days and softening coefficient were increased by64%,86%and64%respectively when15wt%sulphoaluminate cement clinker was doped intodesulfurization building gypsum. The strength and water resistance can be. furtherimproved by co-doping sulphoaluminate cement clinker and ground granulated blastfurnace slag.The flexural and compressive strength for7days and softening coefficient ofdesulfurization building gypsum with15wt%sulphoaluminate cement clinker can befurther increased by28%,50%and15%respectively as15wt%ground granulated blastfurnace slag was incorporated. When more than15wt%ground granulated blast furnaceslag was added, the strength and water resistance decreased dramatically because of thespecimen cracking due to the volumetric expansion of large amount of AFt.The desulfurization gypsum building material with moderate wall thickness, uniformand controllable porosity can be prepared by adjusting the dosage of H2O2and the ratio ofwater to material. pore size of foamed desulfurization gypsum cementing materialsincreased and dry density and strength decreased obviously with the increase of H2O2adding amount and the ratio of water to material. The strength and dry density of foameddesulfurization gypsum cementing materials increased firstly and then reduced as thesodium carboxymethyl cellulose doping anmount increasing. And the strength reachedthe highest value when the dosage of sodium carboxymethyl cellulose was1.0wt%. It isbetter for foaming using water of20o C. Organosilicon waterproofing agent caneffectively improve the softening coefficient of foam desulfurization gypsum cementingmaterials and its dosage should not be more than2.0wt%.