Preparation Of Water-resistant Lightweight Gypsum Panel With High Strength

Heat-insulation materials is of crucial importance for the energy conservation of building. Gypsum-based heat insulation materials exhibit various advantages such as lightweight, fire-resistance, heat preservation, sound insulation, seismic resistance and recycling. The main properties that restrict the expanding use of gypsum are its high water solubility and its tendency to creep in high humidity environments. In this work, a-Calcium sulfate hemihydrate (a-HH) was chosen as raw material for its low hydration heat, low W/H for standard consistency and high strength. The water-resistance, thermal insulation and mechanical strength of gypsum matrix were investigated so as to develop a kind of gypsum pannel which can be used in exterior and humidity environment.In this work, methods of introducing water-resistance to foamed gypsum were firstly adopted to investigate the influences of redispersible latex powder, organosilicon waterproof agent and trisodium trimetaphosphate (STMP) solution on the apparent density, mechanical strength and water-resistant properties. The dosages of redispersible latex powder and concentration of STMP solution were optimized. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were conducted to investigate microstructure of gypsum and phase composition of substances on plaster surface as well as the mechanisms. Then the tea saponin was used as foaming agent to make foamed gypsum, the apparent density, mechanical strength and thermal conductivity models were obtained, followed by the optimization of foaming parameters and setting time.The result shows that redispersible latex powder reduces the water absorption of gypsum pannels, which decreases to15.2%when dosage is8%. The water absorption of gypsum plaster decreases to13.0%after being immersed in organosilicon waterproof agent. The combing use of redispersible latex powder and organosilicon waterproofing agent makes the water absorption decrease to2%and the crystals became short and dense and a layer of organic hydrophobic membrane covered the surface of crystals and filled in the voids. trisodium trimetaphosphate (STMP) solution gains improvement of gypsum strength via substitution of sulfates by dissociated ions, and some phosphate analogue is produced, which makes gypsum less soluble and more suitable for use in humidity environment.Moreover, the results showed that the range of apparent density could be controlled between650kg/m3and1600kg/m3using tea saponin as foaming agent. The mechanical strength and thermal conductivity decreases and heat insulation rises along with the decrease of gypum apparent density. Potassium sulfate and SMF were cooperatively impregnated to adjust setting time efficiently.In the preferred embodiment, the apparent density is747kg/m3,the thermal conductivity is0.19W/mK, the compressive strength is5.5MPa, and the water absorption is5.3%.Obviously it is a kind of water-resistant lightweight gypsum material with high strength.