Surface improvement of scrap rubber by microbially induced carbonate precipitation and its effect on mechanical behavior of rubberised mortar

[Display omitted] •Wasted tyre rubber could be successfully coated with calcium carbonate via MICP.•Adhesion between rubber and cement paste is improved by MICP treatment.•Strength of rubberised mortar after MICP treatment is enhanced significantly.•MICP treatment improves the compatibility between rubber and cement matrix.•MICP treatment reduces the ductility of rubberised mortar. Globally, waste tyres have become a serious ecological threat owing to their low resource utilisation. Rubberised concrete or mortar, including crumb rubber, can consume a part of waste tyres. However, the poor compatibility between crumb rubber and cement matrix reduces the strength of the rubber-cement material significantly, thereby limiting the re-utilisation of waste tyres. In this study, the surface of scrap rubber was modified via microbially induced carbonate precipitation (MICP), and the effect of MICP treatment on the mechanical properties of rubberised mortar, through interface bonding strength test, unconfined compressive strength (UCS) test and impact resistance test, was examined. It was found that calcium carbonate can precipitate on the rubber surface via MICP treatment, thereby enhancing the interface bonding strength between rubber and cement. This improves the UCS of rubberised mortar by 43% at most, which becomes similar to that of ordinary mortar. However, MICP-treated rubberised mortar is brittle and has low impact resistance.