钢筋混凝土构件在各种荷载作用下不可避免地会产生裂缝，裂缝的存在为水分和氯离子等有害介质的侵入提供了便捷通道，从而加速耐久性劣化；水分及溶于其中的氯离子在开裂混凝土中的侵入机理成为混凝土耐久性研究中亟待解决的重要课题，由于常规测试技术的局限性，当前研究还需先进实验手段的支持。本项目应用中子成像技术，力图实现对非透明性混凝土材料在开裂状态下水分和氯离子侵入过程的同步再现和动态成像表征；通过衰减模型推导和后处理程序分析，定量研究开裂混凝土水分和氯离子侵入过程中介质的空间分布规律，以及两者之间的相对滞后现象和多孔基体的过滤机制；基于中子成像和定量分析结果，针对不同材料参数和不同裂缝宽度、深度等裂缝参数以及材料裂缝区和界面区状态，系统揭示开裂混凝土的水分和氯离子侵入机理。为深入研究开裂混凝土的劣化机理及其耐久性评价和寿命预测体系提供理论支持，也为混凝土结构的耐久性研究提供新的研究思路和方法。

Cracks in steel reinforced concrete structures caused by various loads are in most cases inevitable. It is well-known that cracks provide preferential paths for ingress of water and aqueous solutions containing chlorides into cracked structural concrete elements. This process often leads to severe deterioration. Therefore, it is of importance to study the influence of cracks on water and chloride penetration into reinforced concrete elements. However, due to the limitation of traditional testing methods, the study on this topic needs supports from more advanced techniques. In this project neutron imaging, a powerful technique, will be successfully applied to visualize the process of water and chloride penetration into cracked concrete with high spatial resolution. According to the attenuation model and further analysis of the raw data, the spatial water and chloride distributions in cracked concrete during the ingress process are determined in a quantitative way. Neutron imaging is also applied in order to study the difference of penetration fronts between water and chloride ions. The filtration effect of porous cement matrix on chloride ions is also studied. Based on the experimental results and quantitative analysis, the mechanism of water and chloride penetration into cracked reinforced concrete is studied in particular under the conditions of different material parameters, crack parameters such as crack width and crack depth, and situations of cracks and interfaces zone. The obtained results of this project will help to better investigate the deterioration process of cracked reinforced concrete structures and to make proper durability assessment and service life prediction. It also opens a new approach and method for researchers to study further the durability of concrete structures.