Study on Compressive Properties of Self- Healing Cement Paste Using Acoustic Emission and Digital Image Correlation

摘要

Self-healing microencapsulation is a subtle existence in cement mortar. Traditional mechanical test methods cannot comprehensively explain the failure mechanism and failure mode of microencapsulated self-healing cement mortar. Therefore, acoustic emission and digital image correlation are used to monitor the uniaxial compression failure process of self-healing cement paste. A kind of self-healing microcapsule was prepared with sodium silicate and expanded silicate cement as main core materials, and its state in mortar matrix was observed by a scanning electron microscope. Full-field strain and acoustic emission characteristics were obtained and used to analyze the failure mode and mechanism of microencapsulated self-healing cement mortar. The results show that the compressive strength decreases with the increase of the content of microcapsules. According to the analysis of acoustic emission characteristic signal curve, the compression failure process of cement mortar block without microcapsules can be clearly divided into three stages. The change of acoustic emission characteristics of cement mortar after adding microcapsules was captured. In the range of 1～7 %, the acoustic emission hits first increase and then decrease. There are two main reasons for the change: one is the breakage of microcapsules and the other is that the addition of microcapsules changes the pore structure. At the same time, the whole process of compression failure is monitored by Digital Image correlation (DIC). It is found that the cement mortar test block with the appropriate amount of and excessive microcapsules has different failure modes. The results verify and supplement the results of acoustic emission monitoring. Based on the aforementioned indexes, the optimum content of microcapsule is 1～3 %. The research results are of great significance to the design and engineering application of microcapsule self-healing concrete.