Preparation Of Lightweight Fireproof And Heat Insulating Material Based On Fly Ash-based Geopolymer And Study On Its Properties

For years,80% of the fire insulating materials circulated in our market are those inflammable materials which are forbidden in America and European countries. And these inflammable materials have led to fatal accidents. In the meantime, geopolymer is a kind of green inorganic material, which enjoyed unique 3D network structure and excellent compressive strength and anti-high temperature abilities. Hence if we apply the geopolymer technology into fire insulation materials areas, we may get unexpected effects.In order to expand the utilization of fly ash and develop technology appropriate for middle and western parts of China, this article, based on geopolymeric reaction mechanism, used the industrial waste fly ash as the raw material for the synthesis of lightweight fireproof and heat insulating material based on fly ash-based geopolymer, with the aim of synthesizing a kind of inorganic material with favorable properties which can be used in fireproof and heat insulating area.Firstly, techniques including X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffractography (XRD), Fourier transform infrared spectroscopy (FTIR) and laser particle size analysis were performed to characterize the physical and chemical properties of fly ash. Results showed that the fly ashes used in this article are mainly oxides of silicon and aluminum. They consists of spherical articles of different sizes, with D50 of 20.70μm and specific surface area of 1.38 m2/g. Pozzolanic activity tests showed a high activity which could be used for synthesis of geopolymeric material.On top of that, fly ash-based geopolymer lightweight material synthesized through physical foaming method was explored. Results showed that saponification animal fatty acid foam has the largest expansion and longest steady soaking time and was chosen the foaming agent for the following experiment. The optimum ratio of liquid to solid was 0.475; during the synthesizing process, geopolymer slurry should be made first and then followed by addition of foam. Through the control of the amount of foam added, the density of prepared material could be adjusted. When the foaming was 3.3 L/kg fly ash, the material achieved the lowest density being 287.89 kg/m3. The physical foaming method has more complex synthesizing technology and product has the lower compressive strength.Then, this article synthesized lightweight fireproof and heat insulating material based on fly ash-based geopolymer foamed by aluminum powder through single factor analysis. The premium lightweight fireproof and heat insulating material based on fly ash-based geopolymeric material is achieved when ratio of liquid to solid was 0.475, mixing amount of aluminum powder was 2%o, and modulus of water glass at 1.4M and 20% water in the activating solution and stirring time of 10 min. Material synthesized at these parameters exhibited the best pore-sized distribution, dry density and favorable compressive strength.Finally, the synthesized material (foamed by aluminum powder) were characterized for its micro-properties and tested for its macro-performance. The former characterizations showed that a relatively high level geopolymerization had taken place. While the latter tests showed the prepared exhibited good strength, with the compressive strength of materials cured for 3 d,7 d and 28 d being 0.58、0.66 and 1.17 MPa, respectively; the synthesized material showed satisfactory anti-thermal properties, the appearance of material remain intact of exposure to 800℃ for 2 h, and a slightly elevated compressive strength was obtained. The density of synthesized materials were in the range of 500～650 kg/m3, the corresponding heat conductivity coefficient ranged between 0.08-0.11 W/m-K. They displayed better heat-insulating properties than the foamed cement material, the heat conductivity coefficient of which is 0.12 W/m·K. In addition to that, the cost accounting of materials made by the methods described by this article is RMB 132.4～168.6/cubic meter, which is lower than that of the present heat insulating material in the market (usually higher than RMB 200).Through the investigation of this paper, producing lightweight material based on fly ash-based geopolymer proved excellent strength and thermal insulation properties, as well as low cost compared to other heat-insulating materials. It is an effective way to utilize industrial waste fly ash and a promising material in fireproof and heat insulation areas.