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A binary concrete crack self-healing system containing oxygen-releasing tablet and bacteria and its Ca2+-precipitation performance

Zhang, J. L., Wang, C. G., Wang, Q. L., Feng, J. L., Pan, W., Zheng, X. C., Liu, B., Han, N. X., Xing, F., Deng, X.
Applied microbiology and biotechnology 2016 v.100 no.24 pp. 10295-10306
bacteria, bacterial spores, biochemical pathways, calcium, calcium peroxide, concrete, dissolved oxygen, lactic acid, nutrients, oxygen, pH, vegetative cells
A strategy to supply molecular oxygen for microbial calcium precipitation was developed for the first time. Firstly, a controlled oxygen-releasing tablet (ORT) containing CaO₂ and lactic acid with a suitable ratio of 9:1 was developed. It can provide a stable oxygen supply and maintain pH in the range of 9.5–11.0 for 45 days while contacting with water. In the presence of oxygen, a self-healing bacterium H4 spores germinated more effectively and maintained high metabolic activity. Furthermore, H4 vegetative cells induced 50 % more calcium precipitation than that obtained without oxygen supply. Finally, a binary self-healing system containing bacterial spores and ORT was established. The calcium precipitation experiments showed that H4 in the binary self-healing system precipitated 27.5 mM calcium with oxygen supply after 32 days and dissolved oxygen (DO) concentration of the solution decreased from 15 to 4 mg l⁻¹, while only 6.9 mM calcium precipitation was obtained without oxygen supply. This work can disclose the effect of oxygen on microbial calcium precipitation and further lay a foundation for the establishment of ternary self-healing system containing bacteria, ORT, and nutrients, which will be promising for the self-healing of cracks deep inside the concrete structure.