The Preparation And Performance Study Of Porous Thermal Insulation Material Derived From Fly Ash

With the development of global economy, the consumption of energy increases greatly and the problem of energy shortage becomes increasingly prominent. To reduce energy consumption, especially building energy consumption, people pay more and more attention on the study and appliation of porous thermal insulation material. At present, organic thermal insulation material are being widely used in our country because of its good properties, including low desity, high heat-insulation effect and simple construction. However, organic thermal insulation material lacks aging resistance, stability. Besides, its flammability has caused lots of disasters. Inorganic thermal insulation can fill these gaps and may deplace organic thermal insulation material in the near future.The paper first introduces a new kind of porous thermal insulation material using coal fly ash as main raw material by the method of foaming and slip casting process at a relatively fow sintering temperature which is900℃or so and reduces the sintering cost of inorganic thermal insulation. Effects of raw material tatio, solid loading of suspensions, the additive amount of foaming agent and foam surfactants and sintering temperature on the porosity, compressive strength and thermal conductivity were investigated. The results showed that the porosity decreased with the increase of solid loading and sintering temperature and increased with the increase of additive amount of foaming agent while the themal conductivity, desity and compressive strength showed the opposite attendency. Given the thermal conductivity, desity and compressive strength, the optimal raw material ratio is80(fly ash):15(glass):5(clay), the appropriate additive amount of foaming agent is0.3wt%, the solid loading is35wt%and the optimal sintering temperature is900℃. At this experimental condition, the sample has thermal conductivity of0.511W/m.K, porosity of91.1%and compressive strength of0.63MPa. This material can meet the request of thermal insulation material.To further reduce the sintering temperature of inorganic thermal insulation, porous fly ash-based geopolymer material was produced using fly ash and sodium water glass as original material and H2O2as foaming agent according to the characteristic that geopolrmer can be made at ambient temperature or low thermal curing temperature. The changes caused by the geopolymerization and decomposition of H2O2on the properties of the final products were investigated by applying curing on geopolymer mortars with different amounts of sodium water glass (60,80and100g) and H2O2(4,6and8g) added at various curing temperatures (55℃and85℃). As a result, this study confirmed that the ratio of fly ash and sodium water glass, additive amount of H2O2and curing temperature had effects on properties of the samples. Take into consideration the thermal conductivity and compressive strength obtained and the environmental and economic effect, the optimal thermal curing temperature and the amount of sodium water glass and H2O2were55℃,80g and6g, respectively. The sample synthesized at this condition had porosity of79.9%, thermal conductivity of0.0744W/m-K and compressive strength of0.82MPa. Therefore, the reduced preparation cost makes it show promise as thermal insulation material in some situations.To improve the performance of fly ash-based geopolymer, we tried to use cenospheres to replace a part of fly ash. However, the results showed that using cenospheres to replace fly ash was not a good option.