Preparation And Performance Optimization Of Cement-Based Foam Material

With the compulsory implementation of wall material reform and construction energy saving policies, thermal insulation materials for construction are developed rapidly. Traditional organic thermal insulation materials for external wall present advantages of good heat-insulating property, light weight and low cost, but there are various defects, such as flammability and poisonous gases caused by combustion. Under the background, conflicts between construction energy saving and fire resistance are aggravated constantly. Inorganic foam thermal insulation materials, as ideal alternative, are highly favored due to its prominent advantage—high safety. However, there are some problems concerning inorganic foam thermal insulation materials for external wall use, including large volume, water absorption and high heat conductivity coefficient. Therefore, preparing a light and tough inorganic foam heat thermal material, which can be simply prepared and shows features of low heat conductivity coefficient, hydrophobic nature and good comprehensive properties, is an effective method, to remove the conflicts.In this study, the method of combination of experimental test and theoretical analysis,single-factor and multi-factor control variable methods were applied in the paper to determine foaming agent, water cement ratio, foam stabilizer and other additive, to explore different foaming technologies, and finally to prepare a cement-based foam insulation material with proper foaming technology. Strength, performance density, porosity, water absorption, heat conductivity coefficient, and other macroscopic physical and mechanical properties were determined, while SEM and Image-Pro plus (IPP) image processing and analysis software were adopted to characterize internal cellular structure features of the material. The foamed cementitious materials with good dryness, such as dry apparent density of 214kg / m3, water absorption of about 8%, compressive strength of 0.23MPa, thermal conductivity of about 0.049W / (m · K) were successfully prepared. The main research work done is as follows:(1) By testing and comparing foaming ability and foam stability of different foaming agents, a proper foaming agent was screened out; on the basis of comparing advantages and disadvantages between physical foaming and chemical foaming processes for a cement-based cellular material, the new technology integrating physical and chemical foaming processes was presented for preparation of light cement-based cellular materials. Lastly, features and performances of different pore structured obtained through different foaming processes were compared and analyzed, suggesting that the foam prepared by physical foaming process presented optimal comprehensive performances.(2) Hydroxypropyl methyl cellulose (HPMC) was added as a foam stabilizer; measures,including selection of a proper water cement ratio and others, were adopted to regulate cellular structure of the material, to improve internal cellular structure, and to gain favorable thermal insulation property and mechanical property.(3) Based on existing mix proportion and due to the infrared thermal reflecting function,nanometer TiO2 and graphite powder of different admixture amounts were added to reduce heat conductivity coefficient of the material. It was indicated that, when admixture amounts of nanometer TiO2 and graphite powder were 0.5% and 1.0%, the heat conductivity coefficients of the thermal insulation material were 0.0481W/(m·K) and 0.0433W/(m·K) respectively,showing excellent thermal performance.(4) According to the properties of polymer styrene-acrylic emulsion and latex powder with water, it can form closed pore structure of microporous inner wall coating, and study the hydrophobic modification of foam insulation material. The results show that the effect of latex powder on the properties of the composites is better than that of the styrene - acrylic emulsion,and the mechanical properties of the composites are improved while the water absorption properties of the composites are greatly reduced.(5) As polypropylene fiber enhances mechanical engaging force of cement base, it is utilized to optimize mechanical properties of materials, and falling ball impact test was used to characterize improvement of material toughness. Meanwhile, pore structure morphological features and other parameters obtained after mixing fibers were tested and analyzed, while impacts of microcosmic pore structure on macro-properties were discussed. Later, fitting analysis on corrections among different properties was conducted, and suggested certain linear connections.