Li Wenting, Jiang Zhengwu, Yang Zhenghong, Zhao Nan, Yuan Weizhong
Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education, Department of Materials Science and Engineering, Tongji University, Shanghai, People's Republic of China.
PLoS One. 2013 Nov 28;8(11):e81616. doi: 10.1371/journal.pone.0081616. eCollection 2013.
Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks.
水泥基复合材料作为一种易开裂的建筑材料，其自主裂缝愈合对于提高混凝土结构的适用性和延长使用寿命具有重要意义。在本研究中，将包裹环氧树脂作为粘合剂的St-DVB微胶囊嵌入水泥浆体中以实现自愈合能力。首先通过对受损试件养护后的力学恢复来评估自愈合效率。分别采用弯曲和压缩配置来模拟局部和分布裂缝。研究了微胶囊含量、养护条件和损伤程度等因素对愈合效率的影响。创新性地提出通过吸水率来监测和表征愈合过程中裂缝网络的演变。随后通过扫描电子显微镜-能谱仪（SEM-EDS）观察愈合后的裂缝。结果表明，含胶囊的水泥浆体可根据养护条件和损伤程度实现不同程度的力学恢复。但表面活性剂产生的孔隙降低了强度。虽然未观察到明显的刚度提高，但对于损伤程度为60%的试件，断裂能有所增加。随着粘合剂使裂缝愈合，吸水率和吸水量降低，这有助于切断和阻止水分进入。SEM-EDS显微照片也证实，裂缝由硬化的环氧树脂桥接，因为附近裂缝中碳（C）和氧（O）的主要元素质量占比达95%。
