高温热处理对泡沫混凝土结构及性能影响

发布时间：2018-04-29 04:18

  本文选题：泡沫混凝土 + 高温　； 参考：《西南科技大学》2017年硕士论文

【摘要】：物理发泡泡沫混凝土是一种多孔水泥基材料,其制备工艺简便、能够现场浇筑,且同时具备轻质、高强、保温隔热、吸能吸声、抗震等多功能,在建筑围护结构保温、软土地基/废弃矿洞回填、人防工程缓冲等领域有广阔的应用前景。泡沫混凝土主体以无机材料为主,天然具有防火阻燃功能。然而,在火灾环境或窑炉使用条件下,泡沫混凝土围护材料将暴露在高温环境中,水泥水化产物失水、组成/结构演化将加速其力学性能和功能的劣化,因此研究高温热处理对泡沫混凝土结构和性能影响意义重大。本研究以普通硅酸盐水泥为主要原料,采用物理发泡方式制备了密度等级为300-700kg/m~3的泡沫混凝土,研究了高温热处理对不同密度等级泡沫混凝土试件外观、质量损失、抗压强度、导热系数及吸水率等的影响,同时分析了泡沫混凝土气孔结构、物相组成和微观形貌的演化。在此基础上,提出优化配合比设计,以提高泡沫混凝土耐高温性能。研究结果表明:随热处理温度提高,泡沫混凝土质量损失增加、抗压强度降低,吸水率和导热系数增加;密度等级对泡沫混凝土耐高温性能影响较大,300-400kg/m~3密度等级的泡沫混凝土质量和抗压强度损失更大,吸水率增加更多,导热系数先降低后增加;在8 0 0℃时,各密度等级泡沫混凝土基本性能趋于一致,质量损失率为2 0%,质量吸水率为6 5%-7 0%,导热系数为0.3 0-0.3 3,抗压强度残余率为20%。高温热处理后泡沫混凝土孔隙率增大,通孔率增加,气孔孔径无明显变化;不同温度高温处理后各密度等级的泡沫混凝土的水化产物数量和种类变化基本一致,在200℃以下泡沫混凝土主要发生自由水的逸出、水化硅酸钙和钙矾石的分解,400℃时钙矾石完全分解,在600℃时氢氧化钙分解,在800℃时碳酸钙分解。水灰比的增大在800℃以前增大了泡沫混凝土质量损失,但在800℃时影响不大,水灰比0.50-0.55时制备的泡沫混凝土在高温热处理后残余抗压强度更高。粉煤灰、偏高岭土的掺入减小了泡沫混凝土在高温热处理后的质量损失,并提升了强度残余率,硅灰的加入将降低强度残余率。
[Abstract]:Physical foamed foam concrete is a kind of porous cement based material. Its preparation technology is simple, it can be poured in the field, and it also has many functions such as light weight, high strength, heat insulation, energy absorption, sound absorption, seismic resistance and so on. Soft soil foundation / abandoned mine hole backfill, civil air defense engineering buffer and other fields have broad application prospects. The main body of foam concrete is inorganic material, which has the function of fire-proof and flame-retardant. However, under the conditions of fire or kiln use, the foam concrete enclosure will be exposed to high temperature, the hydration products of cement will lose water, and the composition / structure evolution will accelerate the deterioration of its mechanical properties and functions. Therefore, it is of great significance to study the influence of high temperature heat treatment on the structure and properties of foam concrete. In this study, ordinary Portland cement was used as the main raw material to prepare foam concrete with density grade 300-700kg/m~3 by physical foaming method. The appearance, quality loss and compressive strength of foam concrete specimens with different density grades were studied by high temperature heat treatment. The influences of thermal conductivity and water absorption are also analyzed. The evolution of pore structure, phase composition and microstructure of foamed concrete are also analyzed. On this basis, the optimum mix ratio design is proposed to improve the high temperature resistance of foam concrete. The results show that with the increase of heat treatment temperature, the mass loss of foam concrete increases, the compressive strength decreases, and the water absorption and thermal conductivity increase. The density grade has a great influence on the high temperature resistance of foamed concrete. The loss of quality and compressive strength of foamed concrete with density grade 300-400kg / mm3 is greater, the water absorption is increased more, and the thermal conductivity decreases first and then increases. The basic properties of each density grade foam concrete tend to be consistent, the mass loss rate is 20%, the mass water absorption rate is 6 5 -7 0, the thermal conductivity is 0.3 0. 3 3, and the residual rate of compressive strength is 20%. After high temperature heat treatment, the porosity of foamed concrete increases, the through porosity increases, the pore pore size does not change obviously, and the quantity and type of hydration products of different density grades of foamed concrete after different temperature and high temperature treatment are basically the same. Free water escape mainly occurs in foam concrete below 200 鈩，

本文编号：1818353