TEMPERATURE RISE AND DEFORMATION OF CONCRETE SLAB IN CASE OF FIRE

利用相同配合比设计的混凝土试件，对混凝土的导热系数和应力应变关系进行了测试。温度范围为100~800℃，步长为100℃，计算了简支梁在简支梁作用下的受热曲线。阐明了侧向的温度和应力分布。考虑了混凝土的分解。该计算假定混凝土为均匀材料性质，不能计算裂缝或爆炸。另外，在800℃的预热炉上进行了碎石和混凝土在强烈加热下的爆炸实验。测试了安山岩、花岗岩和硅质岩。安山岩没有损坏，花岗岩从晶体界面破裂，大部分硅质岩样品没有损坏，但一些结构不均匀的样品发生了爆炸。对含有上述碎石的混凝土试件进行了试验。夹带的空气由真空泵抽出，在压缩下硬化，以最大限度地减少气孔率。加热后，安山岩出现小裂缝，花岗岩出现大裂缝，硅质岩出现小的表面爆炸。它们只是在碎石试验中是相似的。然后，利用安山岩，用普通方法(孔隙率)制作混凝土试件，并在湿状态下进行测试。加热速度设定为1,000℃/30min。当试件中心达到约250℃时，试件爆炸成小块。这种现象对于湿标本是可以重现的，但对于干标本则不会发生。其原因可以认为与蒸汽爆炸有关。这一现象在文献中尚未见报道。

By using the test pieces of concrete of the same mixture design, the thermal conductivity and stress-strain relation are measured. Temperature range is from 100 to 800℃ with 100℃ steps.Unloaded simple support beam under JIS heating curve is calculated with these data. Temperature and stress distribution in side are clarified. Decomposition of concrete is taken into account. This calculation supposes the homogeneous material property for concrete, and crack or explosion cannot be calculated.Another experiment for explosion of gravel and concrete under intense heating are carried with preheated furnace at 800℃. Andesite, granite and chert are tested. Andesite is not damaged, granite cracked from crystal interfaces, most specimens of chert are not damaged but some specimens not homogeneous texture are exploded. Concrete specimens with above gravel are tested. Entrained air is extracted by vacuum pump and hardened under compression to minimize porosity. After heating small cracks are appeared for andesite, large cracks appeared for granite, and small surface explosion are observed for chert. They are similar for the test of gravel only. Next by using andesite, concrete specimens are made with ordinary method (porosity) and tested in wet state. Heating rate is set to 1000℃/30min. When the center of the specimen reaches to about 250℃, specimen exploded into small pieces. This phenomenon is reproducible for wet specimens, but does not occur for dried specimens. The reason can be considered as to vapor explosion. This phenomenon is not reported yet in literature.