水泥砂浆半浸泡在NaCl-Na2SO4混合溶液中的侵蚀机理

Corrosion mechanism of cement mortars partially immersed in combined NaCl-Na2SO4 solution

针对海洋环境以及中国西部盐湖环境中建筑物经常遭受混合盐半浸泡侵蚀问题,设置变化温度和湿度条件下砂浆试件半浸泡在NaCl-Na2SO4混合侵蚀溶液中,研究NaCl对水泥砂浆在混合溶液中半浸泡侵蚀的影响.运用X射线荧光光谱仪测定离子浓度分布,使用环境扫描电镜、X射线衍射仪和全自动压汞仪等微观方法进行分析.结果表明,Na2SO4单一溶液中砂浆未浸泡区域破坏机理为硫酸钠物理侵蚀;NaCl-Na2SO4混合溶液中,高浓度氯盐能抑制水泥砂浆在混合溶液半浸泡下未浸泡区域的侵蚀,通过在试件表层形成一层NaCl结晶,抑制了Na2SO4物理侵蚀的发生;NaCl对Na2SO4半浸泡的抑制作用在于NaCl结晶填充在表层10~100nm少害孔内,密实表层孔径结构;在砂浆未浸泡区域涂环氧树脂保护层,可以有效降低Na2SO4溶液半浸泡侵蚀破坏.

Aiming at the problem that buildings in marine environment and salt lake environment in Western China often suffer from mixed salt partial immersion erosion, mortar specimens were partially immersed in NaCl-Na 2SO 4 mixed solution under the conditions of daily changing temperature and humidity to explore the effects of NaCl on the salt weathering of Na 2SO 4 solution. The salt ion concentration distribution was determined by X-ray diffractometer(XRD) and other microscopic experiments were carried out by X-ray fluorescence spectrometer emission scanning electron microscope (SEM) and autopore mercury intrusion porosimetry (MIP) to determine the weathering mechanism. The results indicate that the main destruction regime of the drying portion (the upper part) of mortars is due to sulfate physical attack. The high concentration chloride salt can improve the resistance of mortars against Na2SO4 salt weathering by forming a NaCl crystal protective layer on the surface of the specimens;NaCl inhibits the partial immersion erosion of Na2SO4 by filling 10 to 100 nm harmful holes in the surface layer of mortars with NaCl crystals and densifying the pore structure of the surface layer. The epoxy resin coating on the upper part of mortar can effectively reduce the corrosion damage of Na2SO4 solution during partial immersion.