水泥-石灰石粉胶凝材料在硫酸盐侵蚀下的破坏机理

Damage mechanism of cement-ground limestone cementitious material under sulfate attack condition

采用5%硫酸钠溶液,对水泥-石灰石粉胶砂试件进行长期浸泡腐蚀试验,测试试件强度,并对试件进行XRD分析和SEM观察。研究结果表明:在硫酸盐侵蚀下,试件劣化是因产生石膏而不是钙矾石造成的;侵蚀反应还造成水化产物碳铝酸钙分解,促使试件腐蚀破坏;水泥-石灰石粉胶凝材料的破坏主要是由石膏膨胀和水化产物分解共同造成的;在硫酸盐腐蚀环境中,不宜采用石灰石粉作混合材的复合水泥以及用石灰石粉作掺合料的混凝土。

The hardened cement-ground limestone mortar specimens were immersed in 5% Na2SO4 solution. The strengths of the specimens were measured and the microstructures of the specimens were examined by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The experimental results indicate that the deteriorations of specimens are caused by the formation of gypsum, not by ettringite. The decompositions of calcium carboaluminate are caused by sulfate attack and lead to further deterioration of specimens. The main reasons for their deteriorations are gypsum expansion, as well as the decomposition of hydration product. If the environmental conditions can be suspicious of external sulfate attack, the complex cement with ground limestone can not be used and ground limestone can not be used as mineral additives added to concrete.