Research On The Preparation Technology And Performance Of Gypsum Based Compound Insulation Mortar

In our country large amounts of by-products waste gypsums are produced annually. It would not only take up a lot of ground, but also pollute the environment and groundwater resources. Due to the resource utilization of industrial waste gypsum and building energy conservation, gypsum-based cementing composite is prepared with high strength and water resistance by the flue gas desulphurization gypsum and fluorgypsum as base material, the slag as modified material, and additives as portland cement, activator, aquasorb etc. Then using gypsum-based cementing composite as mian cementing to prepare thermal insulation mortar in order to improve the heat preservation performance of gypsum wall materials. Influences of various factors to gypsum-based cementing composite and thermal insulation mortar are investigated systematically.Many significant results are obtained from this study:1. Both strength and water-resistance perform best while using 2%wt coagulant and 2%wt alkali activator in the gypsum-based cementing composite. The bend strength is 7.4MPa, compressive strength is 40.5MPa, and softness coefficient is 0.96. These properties improve a lot comparing with ordinary gypsum products.2. The hydration products of the gypsum-based cementing composite include Calcium sulfate dehydrate, calcium silicate hydrate gel(C-S-H),smack ettringite(AFt) and Ca6Si6O17(OH)2. The more content of C-S-H (gel) in gypsum-based cementing composite, the higher strength, and the better water-resistant performance.3. The structure of hardening gypsum-based cementing composite body is Calcium sulfate dehydrate,Ettringite and Xonotlite crosswise symbiotic crystallization, C-S-H(gel) around them with unreacted slag particles fill the pore. This crystal gel system has dense structure.4. With the amount of expanded perlite and EPS foam particles increasing, dry density, strength, softness coefficient and thermal conductivity decrease. The expanded perlite and paste material form interpenetrating network dense structure, however, EPS particle surface is incompatible with the paste, which will course to form a weak bonding interface. The slag can improve the workability of the morta, and also enhance strength and softness coefficient,increase thermal conductivity. Latex powders increase the bend strength, the bond strength and softness coefficient, but decrease the compressive strength.Organic silica powders reduce water absorption and water absorption rate of the mortar. 5. Two reasonable ratio of thermal insulation mortar are determined from this research. The thermal conductivity of thermal insulation masonry mortar is 0.23W/m·K, compressive strength is 7.1MPa, which meet the requirements of load-bearing insulation masonry mortar, and softness coefficient is 0.92, which exceeds the standard parameter 53%.The thermal conductivity of thermal insulation base coat is 0.053 W/m·K, compressive strength reaches 0.63MPa, which is more than the standard one 32.5%, softness coefficient is 0.67, which is larger than the standard value 34%.6. In this paper, the quantitative relationship of the Gypsum-based thermal insulation mortar dry density and thermal conductivity and the quantitative relationship of the water absorption and thermal conductivity are established.