TEMPERATURE RISE AND DEFORMATION OF CONCRETE SLAB IN CASE OF FIRE

采用相同配合比设计的混凝土试件，测量了其导热系数和应力应变关系。温度范围为100 ~ 800℃，步长为100℃。用这些数据计算了JIS加热曲线下的卸载简支梁。澄清了侧壁的温度和应力分布。考虑了混凝土的分解。该计算假定混凝土材料均质，不能计算裂缝或爆炸。在800℃的预热炉上进行了碎石和混凝土在强加热条件下的爆炸试验。安山岩，花岗岩和燧石进行测试。安山岩未受破坏，花岗岩从晶体界面开裂，燧石大部份未受破坏，但部分质地不均匀的岩石发生爆炸。对含以上砾石的混凝土试件进行试验。夹带的空气被真空泵抽走，并在压缩下硬化，以减少孔隙率。安山岩受热后出现小裂缝，花岗岩受热后出现大裂缝，燧石受热后出现小表面爆炸。它们只适用于砾石试验。其次，利用安山岩，用普通方法（孔隙率法）制作混凝土试件，进行湿态试验。加热速度设定为1000℃/30min。当试样中心温度达到250℃左右时，试样爆炸成小块。这种现象在潮湿的标本中可以重现，但在干燥的标本中不会发生。原因可以认为是蒸汽爆炸。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.