高温诱致水泥浆体微观结构劣化现象的研究

通过扫描电镜观测及压汞试验等微观测试手段,对高温下水泥浆体微观结构劣化进行试验研究。研究表明：随着温度不断升高,水泥浆体表面热开裂由表及里不断延伸、发展,水泥水化产物持续分解,使得水泥浆体内部孔不断粗化,微观结构劣化越来越严重,承载能力持续下降。水泥浆体微观结构劣化从50℃开始萌芽,300℃以后劣化加剧,500℃是水泥浆体的极限承载温度。在温度影响下水泥浆体内部发生的一系列物理化学变化是导致水泥基材料微观结构劣化的本质原因,300℃以后硅酸钙凝胶的持续分解、胶结能力的不断下降以及氢氧化钙的高温分解等化学劣化作用是导致水泥浆体劣化加剧的主要原因,其中硅酸钙凝胶的分解是关键因素。高温对氢氧化钙的劣化影响在300℃就已经开始。

Study on microstructure deterioration of cement paste exposed to elevated temperature

The microstructure deterioration of cement paste exposed to elevated temperatures was investigated by scanning electron microscopy（SEM） observation and mercury intrusion porosimetry（MIP） test.The results show that the thermal cracks develop continuously from the surface to the interior of the cement paste and the hydration products decompose gradually,making the pores of cement paste become more and more coarse and the deterioration of microstructure become more serious,and thus result in a decline of strength of the cement paste.The microstructure deterioration of cement paste begins at 50℃,and becomes more serious at 300℃ and reaches the limit at 500℃.A series of physical and chemical changes in the cement paste due to high temperature lead to the microstructure deterioration of the cement paste.The decomposition and the decline of bonding capacity of C-S-H gel and the decomposition of Ca（OH）2 result in a severe deterioration of cement paste,of which the deterioration of C-S-H gel plays the most important role.The effect of high temperature on Ca（OH）2 deterioration begins at 300℃.