硫酸盐腐蚀对混凝土微观结构特征的影响研究

Influence of Sulfate Corrosion on Microstructure Characteristics of Concrete

为了研究硫酸盐溶液侵蚀作用对混凝土微观结构的损伤规律,对试样进行0次、10次、20次、30次和50次硫酸盐溶液的腐蚀试验,获取了试样外观破坏特征、质量变化曲线、矿物成分、微观形态以及核磁共振T2分布曲线与NMRI图像,在此基础上分析了混凝土腐蚀损伤的微观机理。研究结果表明,随着硫酸盐腐蚀次数的增加,混凝土的质量损失率呈幂指数函数上升规律,材料外观破坏程度逐渐增加;对混凝土微观结构进行SEM和XRD分析,发现硫酸盐腐蚀作用使得钙矾石晶体的含量随腐蚀次数增加而上升;由T2分布谱线的变化趋势表明硫酸盐腐蚀作用使得材料内部小孔隙、中孔隙逐渐扩张成相互连通裂隙;不同损伤程度的混凝土NMRI扫描图像与T2分布曲线变化规律较为同步,说明扫描结果较为准确地反应了试样内部结构;硫酸盐溶液的化学腐蚀与渗透力是导致混凝土微观结构损伤的内在机理。

In order to study the sulfate solution erosion to concrete microstructure damages,the sample under 0,10,20,30 and 50 times of sulfate solution erosion were tested.The characteristics of the appearance of the sample,quality change curve,mineral composition,microstructure and NMR T2 distribution curves and NMRI images were obtained.The micro mechanism of the concrete corrosion damage was analyzed.The results show that with the increase of the number of sulfate corrosion,the mass loss rate of concrete increases as a power exponential function,and the damage degree of material appearance increases gradually.Based on SEM and XRD analysis of concrete microstructure,it is found that the effect of sulfate erosions increases the content of ettringite crystal.The variation trend of T2 distribution curves indicates that the small and medium pores in the sample gradually expand into interconnected large pores due to the action of sulfate erosions.The NMRI scanning images of concrete samples with different damage degrees are in step with the T2 distribution curves,indicating that the scanning results accurately reflected the internal structure of the samples.Based on the tests,it is found that permeation forces and chemical corrosions of sulfate solution are the microcosmic mechanisms that lead to the damage of concrete microstructure.