低导热加气混凝土保温性能与微结构研究

发布时间：2018-03-26 13:06

本文选题：加气混凝土　切入点：导热系数　出处：《东南大学》2015年硕士论文

【摘要】：随着人们生活水平的提高,对居住环境的要求也越来越高,因此建筑耗能成为我国能源消费的大户。在这种背景下,寻求新的建筑材料降低建筑能耗,提高室内环境热舒适度,是我国建材领域面临的新课题。相变材料与传统建材复合成具有储热和温度控制功能的建筑围护结构材料,可以减少室内温度波动,提高环境舒适度。而加气混凝土是一种质轻、节能保温的优秀建材,将二者结合起来势必会对节能减排带来积极影响。但是相变材料应用到加气混凝土中难免会存在稳定性和泄漏的问题,因此研究相变材料在基体中分布以及其对加气混凝土孔结构、力学性能和导热性能的影响和相互关系很有必要。本课题首先通过研究孔结构对加气混凝土性能的影响,总结孔结构对强度、保温性能等方面的影响,结合两相材料传热机理,并综合考虑气孔尺寸与气孔形状对导热系数的影响,从而建立关于导热系数---孔隙率的合适的数学关系模型。然后将模型用于加气混凝士导热系数的实验数据验证分析,并选出特定配比下的最佳导热系数模型。最终确定指数模型拟合度最优,且随着气孔率的逐渐增大,加气混凝土导热系数是逐渐衰减的,并且满足指数衰减模式,不可能存在明显的周期性变化及峰值。研究了纳米二氧化硅(N-SiO2)/石蜡复合相变材料、蒙脱土/膨胀石墨/石蜡复合相变材料在不同掺量的情况下,对加气混凝土宏观和微观性能的影响。结果表明：随着相变材料掺量的增大,相变加气混凝土对应的抗压强度呈现明显的降低趋势,相反干密度随之升高。并且相变加气混凝土导热系数增大,孔隙率减小,断面宏观孔的大小呈明显减小的趋势；在微观结构中,相变材料镶嵌在水化产物的周围,或者附着在结晶较好的托贝莫来石上,从而一定程度上影响了水化产物的水化结晶情况,从而导致储热加气混凝土力学性能降低。研究了相变材料的掺入对微观孔径分布的影响。结果表明：加气混凝土中小于20 nm的无害孔所占的比例较多,而相变加气混凝土中,大于100nm的有害孔所占的比例更大一些,且相变材料掺量越多,所占的比例就越大。从微观孔隙结构说明了相变加气混凝土宏观力学性能降低的原因。为了表征节能保温性能,通过对比实验发现相变储热加气板能够很好地延缓箱体内部温度的升高,能够提高室内的舒适度,对节能减排能够起到明显的效果。并且在强度等力学性能允许的情况下,相变材料的相变潜热值越大,储热节能保温的效果越明显。
[Abstract]:With the improvement of people's living standard, the requirement of living environment is becoming higher and higher. Therefore, building energy consumption has become a major energy consumer in China. Under this background, we seek new building materials to reduce building energy consumption and improve thermal comfort of indoor environment. It is a new subject in the field of building materials in our country. The composite of phase change materials and traditional building materials can reduce the fluctuation of indoor temperature by forming heat storage and temperature control materials. Improve environmental comfort. Aerated concrete is a light, energy-saving and thermal insulation excellent building materials, The combination of the two is bound to have a positive impact on energy conservation and emission reduction. But when phase change materials are applied to aerated concrete, there will inevitably be problems of stability and leakage. Therefore, it is necessary to study the distribution of phase change material in the matrix and its influence on the pore structure, mechanical properties and thermal conductivity of aerated concrete. The effects of pore structure on strength and thermal insulation properties are summarized. Combined with the heat transfer mechanism of two-phase materials, the effects of pore size and pore shape on thermal conductivity are considered synthetically. A suitable mathematical relationship model about thermal conductivity -porosity is established, and then the model is used to verify and analyze the experimental data of heat conductivity of aerated coagulators. Finally, the fitting degree of the exponential model is optimized, and with the increase of porosity, the thermal conductivity of aerated concrete is gradually attenuated, and the exponential attenuation mode is satisfied. It is impossible to have obvious periodic variation and peak value. The nanocrystalline silica N-SiO _ 2 / paraffin wax composite phase change material and the montmorillonite / expanded graphite / paraffin composite phase change material with different contents have been studied. The results show that with the increase of the content of phase change material, the compressive strength of phase change aerated concrete decreases obviously. On the contrary, the dry density increases, and the thermal conductivity increases, the porosity decreases and the macro pore size decreases obviously. In the microstructure, the phase change material is embedded around the hydration product. Or attached to a well-crystallized tobe mullite, which to some extent affects the hydration and crystallization of hydrated products. The effect of phase change material on the micropore size distribution is studied. The results show that the proportion of harmless pores less than 20 nm in the aerated concrete is higher than that in the phase change aerated concrete. The proportion of harmful pores larger than 100nm is larger, and the larger the content of phase change materials, the larger the proportion. From the microstructure of pore structure, the reason for the decrease of macroscopic mechanical properties of phase change aerated concrete is explained. In order to characterize the performance of energy saving and heat preservation, Through the contrast experiment, it is found that the phase change heat storage and aerating board can delay the increase of the temperature inside the box body, improve the indoor comfort, and have obvious effect on energy saving and emission reduction. The larger the latent heat value of phase change material is, the more obvious the effect of heat storage, energy saving and heat preservation is.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528.2;TB34

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