The method of repairing microcracks based on microbiologically induced calcium carbonate precipitation

Cracks will affect the service life of concrete, even if they are small ones. A crack healing method based on biomineralisation is presented to repair microcracks in concrete specimens. By analysing the change in permeability, adopting two different ultrasonic detection methods, and conducting unconfined compressive strength tests, scanning electron microscopy and X-ray diffraction tests, this method of repair was proved to be effective and its repair effect was evaluated. Results show that the permeability of specimens repaired using this healing method declines significantly, but samples with a crack width of 0·05 mm experience a different decreasing trend from those with crack width of 0·15 mm. The unrepaired crack depths of samples with a crack width of 0·15 mm are almost zero, and the smaller the crack widths, the larger the unrepaired crack depths. Using this healing method, samples with wider cracks (0·10 mm and 0·15 mm) are repaired more effectively and regained higher strengths. As a consequence, the healing method can repair small cracks between 0·05 mm and 0·15 mm in concrete, but wider cracks (0·10 mm and 0·15 mm) are repaired more completely and show improved effectiveness of the repair. The healing method and results of repair provide an important reference for subsequent study on the practical repair of microcracks.