A Study on the Preparation of Inorganic Foam Insulation Material
|School||Central South University|
|Keywords||foam cement preparation method foaming liquid cement variety pore structure compressive strength coefficient of thermal conductivity|
The inorganic foam materials have features of light weight、high strength, good heat insulation, good fire-proof performance and environmental protection friendly, architectural insulation engineering in China. However, the foam cement material with apparent density less than300kg/m3exist the problems of low strength, large pore diameter and so on, influencing the performance of application.In the paper, a preparation of the foam cement material with a apparent density less than300kg/m3, compressive strength greater than0.6MPa, coefficient of thermal conductivity less than0.08W/(m-K), pore diameter less than500μm was set as a target. By literature review, It was considered that the constitute of the foaming liquid, the type of cement, the rheological properties of cement paste and the preparation method are the key to prepare the foam cement which possesses the properties we desired. The experiments of foam cement preparation were carried out from the above several aspects and the relationship between the composition, structure and properties of foam materials were discussed. The major experiments and conclusions are as follows:(1) Wet foam mixing method is considered to be the best way to prepare foam cement through a lot of experiments. It is a method that the air compressor make foaming liquid produce wet foam firstly, then mixing the wet foam with cement paste having certain rheological properties and proper setting time, Finally, the well-distributed foam cement paste was setting and hardening at room temperature.(2) It is determined that the foaming liquid were composed of the foaming agent A and the foam stabilizing agent B and water by surface tension, foaming ability and wet foam stability test, the appropriate mass concentration of A is1.5%, and the mass concentration of B increases, the foam stability is better, then, the foaming liquid with different ratio of A/B were used to prepare cement foam material, and the results show that when the mass concentration of B are1%,2%,3%, the apparent density of foam cement are419.3kg/m3,310.8kg/m3,258.7kg/m3, so it can prepare foam cement with different apparent density through the selection of different concentrations of B.(3) In this part, magnesium cement (M), high strength sulphoaluminate cement (HSAC), rapid hardening sulphoaluminate cement (RSAC) were used to prepare foam material and which apparent density and compressive strength were studied. Experiments results show that:magnesium cement (M) is suit for the preparation of foam material with the advantage of low apparent density, thermal conductivity and other properties, but the product had low strength, and always collapsed before hardening, high strength of sulphoaluminate cement (HSAC) has the characteristic of early strength which is good for foam stability, however, the compressive strength of the foam material prepared by HSAC is only0.2MPa with the apparent density of200kg/m3. The compressive strength of the rapid hardening sulphoaluminate cement (RSAC) foam material with the apparent density of343kg/m3can reach0.89MPa, which is consistent with our requirements for preparing light weight and high strength foam material.(4) Through studying on the rheological properties of RSAC slurry with different W/C, adjusting the paste W/C and foam volume ratio, comparing the density and compressive strength performance of foam cement, the optimal mixture ratio of preparation RSAC foam material with density less than300kg/m3was determined:when the mass concentration of A-B was1.5%-3%and water cement ratio of paste was0.5, mixing50%foam、0.37%MT-400and0.57%LiCl.(4) The characteristics of pore structure of RSAC foam material and its related properties were investigated, and the effect of the pore structure on the mechanical properties and thermal conductivity are researched. The conclusions are as follows:the higher the porosity, the lower the apparent density and the compressive strength. When the porosity is high, the water absorption rate is high while the heat conduction coefficient is low. The RSAC foam material with apparent density300kg/m3has a porosity of72%. Most of the pore diameters are less than200μm and the pores above200μm are not more than10%. When the apparent density of foam cement is258.7kg/m3, the compressive strength is0.6MPa, the coefficient of thermal conductivity is close to0.053W/(m·K), but the water absorption rate is as high as63.3%and it requires further research.