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Applied microbiology and biotechnology

A binary concrete crack self-healing system containing oxygen-releasing tablet and bacteria and its Ca(2+)-precipitation performance.


PMID 27459869

Abstract

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 45xa0days 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 50xa0% 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 27.5xa0mM calcium with oxygen supply after 32xa0days and dissolved oxygen (DO) concentration of the solution decreased from 15 to 4xa0mgxa0l(-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.