受硫酸盐腐蚀混凝土微观结构分析

Microstructure analysis of concrete under sulfate corrosion

为探讨硫酸盐腐蚀条件下混凝土微观结构的变化规律,采用干湿交替的实验室加速腐蚀方法对混凝土试件进行腐蚀。通过压汞试验(MIP)测定了不同腐蚀时间混凝土的孔隙率,分析了孔径分布的变化规律;使用扫描电镜(SEM)观测了不同腐蚀时间混凝土微观结构的变化,运用分形理论对不同腐蚀时间混凝土表观裂缝特征进行了分析;采用能谱分析(EDS)测试了不同腐蚀时间混凝土内部相对元素含量的变化。结果表明:硫酸盐腐蚀混凝土的孔隙率先减小后增大,裂缝分维数逐渐增大,元素含量变化显著,微观结构完整性遭到破坏,这与混凝土宏观力学性能的退化相吻合。

To analyze the change of microstructure of concrete under sulfate corrosion, concrete samples exposed to the sulfate solution in wet-dry cycles were prepared in the laboratory. Mercury intrusion test, SEM/EDS analyses were performed on the samples exposed to the sulfate solution for a certain periods. Pore structure and porosity ratio of the concrete samples for various periods were obtained. Microstructure and chemical compounds in the samples for various periods were achieved. Fractal theory was used to describe the crack of concrete under the sulfate corrosion. The results indicated that the porosity ratio of concrete suffered to sulfate corrosion first decreased and then increased. D_f of surface cracks of concrete under the sulfate corrosion increased and relative content of elements changed observably. The integrity of microstructure of concrete under sulfate corrosion was destroyed, which is totally corresponds with the degradation of macro-mechanical properties.