Preparation Of Porous Thermal Insulation Material Based On Fly Ash Using Physical Foaming

Recently, excellent fireproof performance of non-combustible inorganic insulation material gradually got the attention of people since there are many building fire accidents in China cannot be irrelevant with organic heat preservation material of building wall insulation layer. But the performance of inorganic heat preservation material is relatively lower than that of the organic insulation material, resulting in the confined application. In addition, we should also think about how to recycle solid waste, which is generated in the process of industrialization. Therefore, development of high efficient inorganic heat preservation material using high solid waste owns quite strong practical significance. At present, the main research work includes the following aspects:1. The porous thermal insulation material with low thermal conductivity were successfully prepared by using fly ash as main raw material, combining direct foaming method and agar consolidation method. Additionally, the change of property of highly porous thermal insulation material along with different amounts of solid loading of suspensions, agar gelation agents and temperature was systematically researched. The experimental results show that agar gelation agents is the key factor on the basis of same solid loading of suspensions. And we can find that the samples with different amounts of agar gelation agents exhibit similar pore morphology, but the size of pore was relatively larger when the agar concentration was low or high. As the glass powder and sintering temperature increased, the sample with higher strength was achieved, but the porosity is relatively low. At the optimal experimental condition, the sample has thermal conductivity of 0.579 W·m-1·K-1, porosity of 90.35% and compressive strength of 0.60 MPa.2. To reduce the price of sintering and solve the problem of hydrogen peroxide solution foaming method, porous fly ash-based geopolymer material was produced by physical foaming, using fly ash and sodium water glass as original material. Additionally, the change of property of porous fly ash-based geopolymer material along with different amounts of foam, water and water glass was systematically researched. The experimental results show that water and water glass have great influence on the performance of the sample, and the strength of sample was relatively lower when the water glass concentration was low or high. We should note that the additional water is essential when we utilized he moisture in sodium silicate. At the optimal experimental condition, the sample has thermal conductivity of 0.564 W·m-1·K-1 and compressive strength of 0.51 MPa.3. To further improve the performance of porous fly ash-based geopolymer material, we fabricated porous fly ash-based geopolymer/silica aerogel composites with thermal conductivity of 0.480 W·m-1·K-1, compressive strength of 0.71 MPa and water absorption of 0% under the ambient pressure, using sol-gel-immersion method. The experimental results show that high-performance composites can be obtained by inducing nanoscale porous materials into the microporous materials, especially the mechanical property.