高温后碳纳米管混凝土力学性能及细观结构变化

Variation of mechanical property and meso structure of MWCNTs concrete exposed to high temperature

为了探究多壁碳纳米管(MWCNTs)对高温后混凝土力学性能和细微观结构的作用机制,采用单轴压缩、计算机断层扫描(X-ray CT)和电镜扫描(SEM)对高温后MWCNTs增强混凝土的抗压强度、孔径、孔隙率、微观形貌及水化产物的变化趋势进行试验研究.结果表明,高温后MWCNTs增强混凝土强度损失比普通混凝土降低了11.15%~27.60%;MWCNTs的填充和桥接作用可以阻碍并延缓混凝土内部裂缝的扩展,并对600℃以下混凝土内部孔隙网络的形成具有有利影响.分析冷却方式对混凝土性能的影响发现,浸水冷却引发强烈的热冲效应导致混凝土的性能急速下降,短时间的喷淋冷却有利于高温后混凝土性能的恢复,混凝土试样在空气中自然冷却的损伤程度介于上述两者之间.

The action mechanism of multi walled carbon nanotubes(MWCNTs)on the mechanical properties and meso structure of concrete exposed to high temperature was explored.The compressive strength was studied by the uniaxial compression test.The pore characteristics were detected by computer tomography(X-ray CT)technology.The micro morphology and hydration products were observed by scanning electron microscope(SEM).The results showed that the strength loss of MWCNTs in high temperature compared with ordinary plain concrete reinforced concrete decreased by 11.15%—27.60%.The filling and bridging effect of MWCNTs hindered and delayed the expansion of internal cracks in concrete.MWCNTs had a certain beneficial effect on the formation of internal pore network of the concrete below 600℃.The influence of cooling mode on the performance of concrete was also considered.The quench cooling caused a strong thermal shock effect,which led to the rapid decline of performance of concrete.The spray cooling was beneficial to the recovery of properties of concrete exposed to high temperature in a short time.The damage degree of the concrete specimen cooled naturally in air was between the above two.