玻化微珠保温混凝土高温后性能劣化及微观结构

配制普通混凝土（NC）和玻化微珠保温混凝土（GHB/NC），研究从常温升温至1 000℃高温后表观现象变化、质量、抗压强度损失等性能的劣化过程，同时讨论超声波无损检测法评判混凝土高温后性能的普适性，对比分析相对波速、损伤度与受热温度、抗压强度损失率的关系，利用SEM观察不同高温后试件微观结构变化。结果表明:采用相对波速、损伤度评价混凝土高温后性能具有良好相关性，回归公式拟合度较高；随温度升高，NC和GHB/NC混凝土内部损伤逐步加剧，水泥胶凝受热分解、水分散失等在试件表面和内部产生空隙、裂纹并相互贯通，玻化微珠、粗骨料与水泥石界面黏结力逐步减弱甚至丧失，造成宏观力学性能劣化，抗压强度损失率增大。升温至800℃后NC强度损失72.3%，GHB/NC强度损失74.6%，1 000℃时基本丧失承载能力。 

Performance degradation and microscopic structure of glazed hollow bead insulation normal concrete after exposure to high temperature

The normal concrete (NC) and glazed hollow bead insulation normal concrete (GHB/NC) were made for studying the process of performance degradation from normal temperature to 1 000℃, which including changes in apparent phenomena, loss of mass and compressive strength. Simultaneously, the adaptation of ultrasonic test in evaluating the performance of concrete after exposure to high temperature was investigated. The relationships between relative velocity, damage degree and temperature, compressive strength loss rate were comparative analyzed. The micro-structure changes of concrete specimens after exposure to different high temperatures were observed by SEM. The results show that it has good correlation of the parameters of relative velocity and damage degree in evaluating the performance of concrete after high temperature. The regression formula has a good fitting degree. With the rise of heat temperature, the internal damage of concrete is gradually intensified, cement hydrates decomposes and water disperses, which causes voids, cracks and interpenetration occurred on the surface and inside of the specimens. The bonding force between glazed hollow bead, coarse aggregates and cement paste is gradually weakened or even lost. These cause deterioration of macroscopic mechanical properties and increasing of compressive strength loss rate of GHB/NC and NC. After experiencing the high temperature of 800℃, the losses in compressive strength of NC and GHB/NC are 72.3% and 74.6%, and the bearing capacity is almost lost after exposure to 1 000℃.