Microbial repair materials based on sodium alginate modification for mortar crack repair

In response to the shortcomings of traditional concrete crack repair materials, a new generation of repair materials was developed - a microbial repair material (MRM) based on sodium alginate modification. A brushing technique is used to fix microorganisms on the cracks to be repaired so that they can deposit calcium carbonate (CaCO3) in situ to repair the cracks. The fundamental properties of the MRM were studied, along with the macroscopic morphology and surface water absorption of specimens before and after the repair of mortar cracks. The material changes and microstructure of the repair products were also analysed. The results showed that the calcium carbonate content, water absorption ratio and heating shrinkage rate of the MRM with modified sodium alginate were better than those of the repair material without microorganisms. It was also found that the microorganisms were fixed in cracks on the surface of the mortar using the brushing technique with sodium alginate as the carrier. They adhered tightly to the cracks after only two repairs and produced repair products (mainly calcium alginate and calcium carbonate) and the surface water absorption ratio was reduced by about 65% compared with that before repair.