基于海洋环境浪溅区长期暴露试验的偏高岭土混凝土耐久性研究

Research on Durability of Metakaolin Concrete Based on Long-Term Exposure Experiment at In-Situ Marine Splash Zone

采用偏高岭土单掺以及与粉煤灰复掺取代水泥配制混凝土,在实际海洋环境浪溅区开展长期暴露试验,测试了暴露混凝土中的总氯离子含量和自由氯离子含量,采用SEM-EDS测试了混凝土的水化产物形貌与元素分布,并采用XRD分析了暴露混凝土的物相组成.结果表明:偏高岭土可降低实际海洋环境下混凝土中的氯离子含量和氯离子扩散系数,提升混凝土的氯离子固化能力,当与粉煤灰复掺时效果更佳.偏高岭土改善混凝土抗氯离子渗透性的机理在于其改善了混凝土的结构密实性,提高了水化凝胶的Al/Si比,降低了混凝土的碱性,促进了暴露混凝土中F盐的生成.此外,偏高岭土对于实际海洋环境下混凝土的长期抗硫酸盐侵蚀性没有不良影响.

Concrete containing metakaolin(MK) and the ternary blends of MK and fly ash(FA) were prepared and used to conduct a long-term exposure experiment at in-situ marine splash zone. Then, the total and free chloride contents of the exposed concretes were tested, and the morphology and element composition of the hydrates in the concretes were tested by means of SEM-EDS. Moreover, the phase component of the exposed concretes was measured by means of XRD. The results show that the chloride content and chloride diffusion coefficient of concrete in actual marine environment both decrease with the application of MK, while the chloride binding capacity improves, especially in the presence of FA. A denser structure of concrete can be obtained by the use of MK. Higher Al/Si ratio and lower alkalinity of the hydrates of MK concretes promote the formation of Friedel’s salt. In addition, the application of MK has no detrimental effect on the sulfate resistance of long-term exposed concretes.