氯化铵加速侵蚀下混凝土性能劣化及微观机理影响研究

Study on the Deterioration of Concrete Performance and the Influence of Microscopic Mechanism under Accelerated Erosion of Ammonium Chloride

为研究氯化铵侵蚀作用下混凝土性能的劣化,将混凝土浸泡在6 mol/L氯化铵溶液中,测定混凝土的力学性能、侵蚀深度,通过计算侵蚀龄期下试件的含水率和饱和度来表征孔结构的变化,采用扫描电子显微镜表征和分析试件内部物相变化以及形貌特征。结果表明:在氯化铵侵蚀环境下,随侵蚀时间的增加,混凝土的侵蚀深度逐渐增加,孔隙率增加显著;与标准养护环境相比,侵蚀初期混凝土的抗压强度增大,而侵蚀60~90 d混凝土的抗压强度降低;侵蚀环境下混凝土的含水率明显增加,而试件饱和度却与之相反;氯化铵侵蚀混凝土内部生成的钙矾石和弗雷德尔盐是混凝土后期裂缝发展的主要原因。

In order to study the deterioration of concrete performance under the action of ammonium chloride erosion,the concrete was immersed in 6 mol/L NH 4 Cl solution,and the mechanical properties and erosion depth of the concrete were measured.The changes of pore structure were characterized by calculating the water content and saturation of the specimens under the erosion age,and the internal phase changes and morphological characteristics of the specimens were characterized and analyzed by scanning electron microscopy.The results show that in the environment of ammonium chloride erosion,with the increase of erosion time,the erosion depth of concrete increases gradually,and the porosity increases significantly.Compared with the standard curing environment,the compressive strength of concrete at the initial stage of erosion increases,while the compressive strength of concrete at 60~90 days of erosion decreases.The water content of concrete increases significantly under the erosion environment,while the saturation of the specimen is opposite.The erosion of ettringite and Friedel′s salt generated inside the concrete by ammonium chloride is the main reason for the development of cracks in the later stage of concrete.