盐渍土环境下混凝土中SO4^2-扩散性试验研究

为了研究西部盐渍土环境下混凝土中SO4^2-的扩散性,测试了在不同溶液、不同干湿循环龄期下,混凝土中不同深度的SO42-含量。采用Fick第二定律为基本模型,考虑SO42-与混凝土结合能力以及混凝土为非均匀介质的特性,对SO42-扩散系数进行了分析讨论。此外,基于XRD结果,分析了侵蚀过程中钙矾石的生长情况以解释说明钙矾石的生成对SO4^2-扩散性的影响。结果表明,Cl-可促进侵蚀前期SO4^2-的侵蚀速度;西部盐渍土环境下混凝土中SO4^2-的扩散系数与结合能力呈负相关关系,与侵蚀深度呈正相关关系;SO4^2-浓度越高,钙矾石生长越快,钙矾石膨胀作用会填充混凝土的既有裂缝,从而抑制SO42-扩散。

Study on the Diffusion of Sulfate Ions in Concrete Under the Saline Soil Environment

In order to study the diffusion of sulfate ions in concrete under the saline soil environment in western China, the content of sulfate ions in concrete at different depths in different solutions and at different wet-dry cycle ages was determined. Fick second law was adopted as the basic model. Considering the ability of sulfate ions to bond with concrete and the characteristics of concrete as non-uniform medium, the diffusion coefficient of sulfate ions was analyzed and discussed. At the same time, ettringite crystal structure was refined according to the X-ray diffraction results of concrete samples after erosion, and the growth of ettringite during erosion was analyzed, so as to explain the influence of ettringite generation on the diffusion of sulfate ions. The results show that chloride ion can promote the erosion rate of sulfate ion in the early stage of erosion. There is a negative correlation between the diffusion coefficient and binding capacity of sulfate ions in the saline soil of western China, and a positive correlation between it and the depth of erosion.The higher the concentration of sulfate ions, the faster the growth of ettringite. The expansion of ettringite will fill the existing cracks of concrete to inhibite the diffusion of sulfate.