电化学除氯处理后的混凝土微观结构研究

为了研究电化学除氯对混凝土中离子分布和微观结构的影响规律,采用压汞法、SEM电子显微镜分析等方法对电化学除氯后不同水灰比混凝土试件中钢筋附近和表面层的氯离子和钾钠离子含量、孔隙结构、显微结构进行对比分析.结果显示,电化学除氯后,钢筋附近混凝土与外层混凝土相比,氯离子含量约为1/2,钾离子含量约为5～10倍,钠离子含量约为8～18倍,水化物颗粒间结合不连续、部分水化产物分解.钢筋附近区域混凝土中的氯离子含量明显低于外表层混凝土,钾、钠离子在钢筋阴极附近大量聚集.经过电化学处理后的混凝土试件钢筋附近区域的孔隙率和大孔含量增多,结构疏松;而外表层混凝土结构致密,孔隙细化,水化产物成网络状结合良好.

Microstructure of concrete after electrochemical chloride extraction treatment

The mercury intrusion method and the scanning electron microscopic (SEM) method were used to study the influence of electrochemical chloride extraction treatment on the distribution and microstructures of ions in concrete. Samples were selected from the zone near steel reinforcement and the outer surfaces of concrete specimens with different water to cement ratios after electrochemical chloride extraction (ECE) treatment. Chloride ion, potassium ion and sodium ion content, pore structure and microstructure were tested on these samples. The results show that after the ECE treatment ion content near steel for chloride ions, potassium ions and sodium ions, are respectively 1/2, 5～10 times and 8～18 times their concentrations in the outer surface. Meanwhile, there were some discontinuous granular hydration products and a little decomposed hydration calcium silicate hydrate (CSH) gels. However, a great deal of potassium ions and sodium ions accumulated near the steel where there was much less concentration of chloride ions than in the outer surface of the concrete. After the ECE treatment, the concrete near the steel presented a higher porosity with more coarse pores and a weak microstructure. On the contrary, the outer surface concrete showed a compact microstructure with smaller pores and an intact hydration product network.