Study On Insulation Performance And Microstructure Of Autoclaved Aerated Concrete With Low Thermal Conductivity

With the improvement of living standard, people’s requirement for living environment is higher and higher, so building energy consumption has become a large energy consumer in our country. In this context, looking for new building materials to reduce building energy consumption and improving the comfort level for the indoor environment have become a new topic for the field. Nowadays, we combined traditional building materials with phase change materials (PCM) to make new building palisade structure materials which had function of storing heat and controlling temperature. Its can reduce indoor temperature fluctuation and provide a comfortable environment. Also Autoclaved aerated concrete (AAC) is a kind of light and energy-saving building material, it can bring us a positive impact on energy saving and emission reduction if we combined the two materials together. But the problem of stability and leakage still inevitably exist during the phase change materials used in autoclaved aerated concrete, so how to study the phase change materials in the substrate distribution and the relationship between aerated concrete pore structure, mechanical properties and thermal performance is becoming more and more necessary.First of all, through the study of pore structure on the properties of aerated concrete, we summarized the effect of pore structure on strength and insulation performance. Then we combined with two-phase heat transfer mechanism of the material and considered the influence of pore size and pore shape on thermal conductivity of autoclaved aerated concrete to establish a suitable mathematical model on thermal conductivity and porosity. After that, we put the model used for aerated concrete analysis of experimental data validation, and chose the best model for the specific proportion. Eventually we found the optimal fit model was index model, and the thermal conductivity was reduced with the growth of porosity. The thermal conductivity was satisfied with the index attenuation model; there can be no obvious cyclical change.Secondly, under the different dosage, we studied how the nano-silica dioxide/paraffin composite phase change materials and montmorillonitel/expanded graphite/paraffin composite phase change materials to affect the properties of aerated concrete macroscopic and microscopic. The result showed that with the increase of dosage of phase change materials, the compressive strength of AAC was obviously decreased, instead of dry density increased. And the thermal conductivity was increased with the decrease of porosity. Also the section macro-pore size was significantly decreased. In the microstructure, phase change materials set around the hydration products and adhered to the good tobermorite to affect the hydration of hydration products, resulted in AAC mechanics performance decreased.And the incorporation of phase change materials was studied on the influence of micro-pore size distribution. The results showed that the holes diameter of AAC in less than 20 nm was harmless hole, and the proportion was more than others. But in the phase change aerated concrete, the proportion of greater than 100 nm harmful holes were much more, the more the dosage of phase change materials, the more the greater of the proportion. It was showed the reason why mechanics performance decreased of phase change aerated concrete from microscopic pore structure.In order to represent the performance of energy-saving, we found that the phase change thermal storage materials can effectively delay the internal temperature rise of box body through the contrast experiment. The phase change materials can improve the comfort level and have obvious effect of energy conservation and emissions reduction. And under the permission of the mechanical properties, the bigger the phase change latent heat of phase change materials, the more obviously effect of thermal insulation energy-saving.