Interactions between Organic Chelation Agents and Ions in Seawater for Accelerating Self-Healing of Cracks in Cement Paste

作者：Liu, Hao; Huang, Haoliang^*; Wu, Xintong; Wu, Kai; Hu, Jie; Wei, Jiangxiong; Yu, Qijun

来源：JOURNAL OF MATERIALS IN CIVIL ENGINEERING, 2021, 33(4): 04021036.

DOI：10.1061/(ASCE)MT.1943-5533.0003639

• Self-healing
• Organic chelation agents
• Crack closure ratio
• Self-healing products
• Marine environment

To improve the durability of cracked concrete structures in a marine environment by self-healing of cracks, the efficiency and speed of self-healing need to be increased. In this study, the interactions between organic chelation agents, i.e., tetrasodium ethylenediaminetetraacetic acid (EDTA-4Na), triethanolamine (TEA), and sodium hexametaphosphate (SHMP), and ions in seawater for accelerating crack self-healing were investigated. After self-healing for 1 day, the closure ratio of cracks of an initial width of 400 mu m increased from 5% to 80%, 65%, and 90% when 1.5% (by weight of cement) EDTA-4Na, SHMP, and TEA were admixed, respectively. However, the distribution of self-healing products in surface cracks of specimens with organic chelation agents was nonuniform in the early stages of healing, resulting in the large scatter-in terms of the standard deviation and range-of the values of the crack closure ratio. As the self-healing products gradually formed and accumulated in surface cracks, the standard deviation and range gradually decreased. Furthermore, in specimens with 1.5% triethanolamine, after seawater immersion for 1 day, a thin about 250-mu m-thick layer of Mg(OH)2 formed at the crack mouths. During self-healing for 28 days, this thin layer extended inward up to a depth of 3 mm. To investigate the accelerator mechanism, the mineralogy of the self-healing products was characterized. When EDTA-4Na and SHMP were used, the main minerals were portlandite, brucite, aragonite, and calcite, while there was no portlandite when TEA was used.

• 单位
  同济大学