冷热循环负荷作用下混凝土微观形貌分析

Microscopic analysis on hardened portland cement concrete under thermal cycles

利用扫描电镜(SEM)观察分析了冷热循环负荷作用下硅酸盐混凝土微观形貌的变化。结果表明,200℃条件下硅酸盐混凝土的水化产物和结构没有明显变化;而经过15次20℃-250℃-20℃的冷热循环后,混凝土中水化硅酸钙的形貌由絮状向点滴状转变,片层状C(a OH)2发生一定程度的裂解,硬化浆体内部出现少量因高温-冷却过程造成的裂隙;混凝土抗压强度降低比较明显。

The microstructure of heat resistant Porland cement concrete under different thermal cycling conditions were investigated by Scanning Electron Microscope （SEM）.The results show that the microstructure of concrete has no distinct change during 20℃-200℃-20℃ cycles. However, after 15 times of 20℃ -250℃-20℃ cycle the microstructurc of C-S-H in concrete is trausferred from gelatinous to teardrop, Ca（OH ）2 appears to rupture to some extent and a few visable cracks are yielded in the paste of concrete. Simultaneously, the compressive strength of concrete falls markedly.