Abstract
This research investigated the self-healing potential of early age cracks in cement-based materials incorporating the bacteria which can produce carbonic anhydrase. Cement-based materials specimens were pre-cracked at the age of 7, 14, 28, 60 days to study the repair ability influenced by cracking time, the width of cracks were between 0.1 and 1.0 mm to study the healing rate influenced by width of cracks. The experimental results indicated that the bacteria showed excellent repairing ability to small cracks formed at early age of 7 days, cracks below 0.4 mm was almost completely closed. The repair effect reduced with the increasing of cracking age. Cracks width influenced self-healing effectiveness significantly. The transportation of CO2and Ca2+ controlled the self-healing process. The computer simulation analyses revealed the self-healing process and mechanism of microbiologically precipitation induced by bacteria and the depth of precipitated CaCO3 could be predicted base on valid Ca2+.
Highlights
With low tensile strength, concrete may take cracks during its service life (Bang et al, 2010)
It can be seen that crack was almost filled completely after 5 days in Group 4 which cooperated with self-healing agent
The results indicated that the flexural strength of specimens repaired with nutrient and bacteria could be increased 40, 90.9, and 110% than other self-healing agent (G3, G2, and G1), respectively
Summary
Concrete may take cracks during its service life (Bang et al, 2010). Cracking is one of the main factors causing the degradation of concrete durability. Repairing timely or self-healing for cracks may extend the service-life of concrete structures (Wang et al, 2014). Inspection and maintenance techniques for concrete structures have become the focus of interesting attention. The traditional repair methods such as cement grouting and maintenance are all difficult and expensive. Under such circumstances, the ability of self-healing cracks in concrete raised wide spread attention
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