Preparation And Performance Investigation Of Inorganic Thermal Insulation Materials For Building Exterior Wall By Foaming And Setting Method

In recent years, due to a lack of corresponding fire prevention codes, a lot of combustible organic insulation materials are used in building exterior walls, resulting in frequent occurrence of fire accidents. Now in China, the most prominent problem in building exterior insulation technology is the contradiction between energy conservation and fire prevention. Although organic insulation materials have excellent insulation performance, light weight and cheap cost, they are flammable. Once ignited, organic insulation materials will release a lot of heat, smoke and toxic gases, and furthermore the flame will quickly spread on the building facade, resulting in serious consequences. Inorganic insulation materials have outstanding fire performance, but they have large thermal conductivity, high water absorption and low energy conservation efficiency. Considering fire prevention priority, this paper proposed preparing a low thermal conductivity, low cost, environmentally friendly and hydrophobic inorganic insulation materials for building exterior walls.In this paper, through combining theory and experiments, inorganic porous insulation materials with a low thermal conductivity, suitable strength, and hydrophobic were prepared using foaming and setting method. The main research work is as follows:First, the heat transfer mechanism in porous thermal insulation material was studied. A novel effective medium theory was developed to describe the internal heat transfer of porous thermal insulation material. The mathematical expression of the theory was deduced by heat transfer analysis and the validity of the theory was also verified. According to the model, the thermal conductivity of porous materials can be decreased through three approaches, increasing porosity (or decreasing bulk density), decreasing the thermal conductivity of solid skeleton and holding a reasonable pore structure. This work provided theory basis for the whole research work.Then, industrial mullite powder and corn starch are used as the aggregate and cementing materials respectively and highly porous mullite insulation materials were prepared by foaming and starch consolidation method. The thermal conductivity of highest porosity sample can reach0.1W/mK. This work provided experimental basis for further research work.Next, aiming at the shortcomings of foaming and starch consolidation method, more economic and environmentally friendly cementing material cement are used to substitute corn starch and porous mullite insulation materials were prepared by foaming and cement consolidation method. This method solved the problem of the cost and discharge of organic material, and optimized the preparation method.Finally, lower cost and lighter weight industrial waste fly ash and cement were used as the aggregate and cementing material respectively for preparing fly ash based porous insulation material. Moreover, lower thermal conductivity samples were prepared by using foaming agent foaming independently first and then mixing with slurry instead of direct foaming method. In addition, samples were treated by water proof agent, and after the treatment samples became hydrophobic.