Review of Various Microbial Immobilization Methods Towards Self-healing Application

Abstract

Crack development and propagation in concrete structures, associated with internal and external stresses possess a severe threat to the performance and durability. Repair works of such concrete structures impart an immense financial toll. Self-healing mortar and concrete are developed with a view to provide a solution to address the aforementioned problem. The viability and performance of calcite precipitating microbes inside the concrete, in the long term, is always a concern when it comes to self-healing application. Among different methods to introduce such bacteria inside, immobilisation is considered to yield better results having the advantage of lesser impact from the adverse environment. This paper reviews the available immobilisation and encapsulation methods for microbial transport into the mortar or concrete, which makes use of porous media, hydrogels, polymeric coatings, etc., and its effectiveness in making a resilient building material. The current practices and the challenges associated with encapsulation methods to make a viable bio-mortar is critically reviewed and presented. The interaction of microbial colonies with the transporting medium and crack healing efficiency is compared based on different encapsulation methods. An experimental study was conducted to determine the impact of nutrients on the compressive strength of cement mortar was also conducted to identify the impact on strength parameters. The nutrients like calcium lactate, calcium nitrate, urea, calcium formate, and yeast extract in different dosages were analysed to achieve the optimum dosage value. It was observed nutrients other than urea and yeast extract, improved the compressive strength of bio-mortar at respective optimum dosages. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.