|
To order to develop new wall materials with fine properties of keeping warm, beinglight, refractory, water-proof, strong, and low-shrinkage, the new magnesite cementingmaterials—magnesium oxysulfate cement combined with citric acid(that is,magnesium-oxysulfate-citric cement abbreviated as MOCC) were used as the cementingmaterials. The light aggregate, water-proof materials, anti-crack fiber and blowing agentwere added. New thermal-insulation wall materials are developed through the orthogonaltest, whose properties are fine in terms of fireproofing, heat conduction, density, strength,rate of water asorption, and contractility. Through modern testing methods—XRD andthree-dimensional super-depth-of-field microscope VHX-2000, the composition andmicrostructure of the thermal-insulation materials were analyzed. The major results arelisted in several respects as follows.The properties of magnesium-citric cement were examined, When mixing proportionwas MgO/MgSO4=1.7, H2O/MgSO4=1, citric acid content=1.3%. The28d compressivestrength and flexural strength of this kind of magnesium oxysulfate cement could be up to50.90MPa and9.29MPa respectively. Through single-factor experiment, MOCC’sinsulation board was derminted to be a compound system made up of lightweight aggregate,hydrophobic agent, fiber and blowing agent added by air bubble.The major properties which affect the themal-insulation wall materials are thematerials’ density, rate of water asorption, compressive strength and thermal conductivity.Through the orthogonal test, the four properties were measured and analyzed. The effects ofaggregate-cement ratio, addition of blowing agent, fibers content and addition ofhydrophobic agent on each property were discussed. It concluded that the best mixproportion was aggregate-cement ratio0.2, addition of blowing agent0.09, fibers content0.4%， and addition of hydrophobic agent1.2%. After the reexamination of the best mixproportion‘s property, an insulation board was obtained with its density306kg·m-3,thermal conductivity0.072W/m·k, compressive strength0.84MPa, breaking strength0.56MPa, rate of water asorptioin16.8%, linear contraction and cost21.5元/m2.When the air bubble was added, the composition of MOCC was not changed, whereasits inner pore structure was changed. Thus, the new blowing-cement insulation board possess fine macroproperties. The best pore structure is the abundant, uniform, tinyand closed circular hole resulting from the inner parts of the hardened materials.
|