Study On Thermal Properties And Applied Technology Of Lightweight Cellular Wall Materials

The project was divided into three parts in this paper:experimental study on thermal performance of lightweight porous wall materials, experimental study on heat-transfer characteristics of lightweight insulation board with different laminated composites, and experimental study on mechanical properties of flexible binding mortar in external insulation engineering, respectively.(1) The experimental study on thermal performance of lightweight porous wall materials included the experiment of thermal performance and heat storage of ceramsite cellular concrete(CCC) and the experiment of heat transfer performance of lightweight porous wall materials.For the experiment of thermal performance and heat storage of CCC,18groups of specimens with the design density ranging from from600to1100kg/m3were prepared, and the coefficients of thermal conductivity and heat storage of the specimens were measured in guarded hot plate method and environmental balance method, respectively. In addition, the porosity and the compressive strength were measured as well. The results showed, thermal storage coefficient is approximately15times of thermal conductivity for CCC with the same density. The lowest thermal conductivity of0.137W/m K was obtained from the specimen (DD-600) with the oven dry density of498kg/m3. In addition, it was obtained by fitting analysis that polynomial model formula derived to accurately estimate thermal conductivity through oven dry density, porosity and compressive strength and an approximately linear model formula between thermal conductivity and temperature difference. Furthermore, the effect of ceramsite volume proportion on the thermal conductivity was discussed, and the optimum ceramsite volume proportion was45%for CCC with the design density of600kg/m3.For the experiment of heat transfer performance of lightweight porous wall materials, five kinds of masonry materials including CCC block, aerated concrete block, clay brick and fine stone concrete hollow blocks with or without EPS filling were studied in this paper. Multi-material envelope test model was created with the masonry materials above, and heat transfer coefficients of corresponding walls were measured with the method of heat flow meter. Thermal stability of the walls and effects of regular variations of temperature difference, ambient temperature and the distribution of temperature sensors on heat transfer coefficient were analyzed. Heat transfer coefficient of CCC block wall was calculated according to thermal conductivity of CCC with the same density, and the calculated value was in good agreement with the test value by multi-material envelope test model, which corroborated the feasibility of heat transfer performance test method. In addition, basing on formula for calculating the thermal resistance of composite wall and considering multi-dimensional heat transfer, the thermal resistance formula considering geometric correction coefficient was obtained.(2) For the experimental study on heat-transfer characteristics of lightweight insulation board with different laminated composites, it was synchronously measured with the method of heat flow meter that the coefficients of heat transfer of the boards with different insulation thickness, different density and different structural form. The results showed that the heat transfer coefficient of the internal insulation was approximate to that of the external insulation, however, heat transfer coefficient of the sandwiched insulation was a little higher. In addition, the heat transfer coefficient of the laminated board of60mm normal conrete layer together with100mm CCC layer was about1.0W/m2-K, and it could basically satisfy the energy efficiency design standard of public buildings in the hot summer and cold winter zone. The temperature and heat flux of the laminated boards over one cycle were tested and analyzed, and it was obtained that external insulation was ideal structural form for the laminated boards. In addition, the interface bonding strength and the durability both conformed to technical index in external insulation engineering.(3) For the experimental study on mechanical properties flexible binding mortar in external insulation engineering, this paper studied the effect of cement-sand ratio, water-binder ratio and polymer additives on the mechanical properties of binding mortar with the method of orthogonal test, including compressive strength, flexural strength, ratio of flexural to compressive strength and adhesive strength. Binding mortar mix with good flexibility and workability, especially high adhesive strength was developed. Meanwhile, Regular changes of strength indexes of the optimum mortar depended on age, curing condition, mixing process and the strength grade of cement were explored. In addition, the pullout test of the optimal mortar on both foam ceramic and ceramsite foam concrete as well as the durability test were carried out, and the results conformed to technical index in external insulation engineering.