Investigation On That Preparation And Performance Of Water-resistant Desulfurization Gypsum Base Insulation Materials

Desulfurized gypsum is a kind of solid waste from flue gas desulphurization in thermal power plant,and the production is huge.The chemical composition and properties of desulfurized gypsum are similar to that of natural gypsum.It is a suitable substitute for natural gypsum.Therefore,as the main cementitious material,the influence of retarder,water reducer,mineral admixture,water-soluble polymer and fiber on the performance and modification mechanism of desulfurized building gypsum were studied in the research.Meanwhile,adding with expanded polyphenyl particles and sand,the desulfurization gypsum base thermal insulation material with water resistance and heat preservation was studied and prepared.The main conclusions of the experimental study were as follows:（1）Citric acid,sodium gluconate,sodium tripolyphosphate,and sodium hexametaphosphate had retarding effect and decreased the strength of desulphurized gypsumin different degrees.When the retarders was combined,the retarding effect could be improved Under the same retarding effect,the compressive strength of desulfurized gypsum with combined retarder was higher than that of one with a single retarder.The strength loss of gypsum was the least when citric acid and sodium gluconate were mixed together.（2）Water reducing agent could effectively reduced the water requirement of desulfurized gypsum.When the content of naphthalene-based water reducer was 0.9%,the strength of desulfurized gypsum appeared maximum,the maximum flexural strength was 3.91MPa,and the maximum compressive strength was 10.88 MPa.When the content of polycarboxylic acid superplasticizer was 0.15%,the strength reached the maximum value at 2h and 7d,which was higher than that of desulfurized gypsum without superplasticizer.（3）The absolute dry strength of desulfurize gypsum could be improved by adding with slag powder or cement.However,slag could reduce the softening coefficient of desulfurized gypsum cementitious material,which was not conducive to improve the water resistance of desulfurized gypsum.When the content of cement was 4%,the water resistance of desulfurized gypsum could be improved.When slag and cement were added together,the water resistance of desulfurized gypsum was improved effectively.The optimal content of slag and cement was:slag 8%,cement 4%,the softening coefficient was 0.81,the water absorption rate was 5.6%.（4）Polyvinyl alcohol fiber could improve the strengths of desulfurized gypsum,especially the flexural strength,but the effect was not obvious.Water-soluble polymer had little effect on the strengths of gypsum at low dosage,but the strength of desulfurized gypsum decreased with the increase of dosage.（5）The proportioning parameters of desulfurized gypsum-base thermal insulation materials with better comprehensive properties were optimized and determined.It was qualified for excellent flexural strength of 3.15 MPa and compressive strength of 8.21MPa,the dry surface density was 751 kg/m³,the water absorption was 6.0%,the soft coefficient was 0.80 and the thermal conductivity was 0.1685 W·（m·K）^-1.