A Novel Non-Axenic Granulated Culture Based Microbial Self-Healing Concrete

Construction and demolition wastes (CDW) such as concrete, brick, plaster, wood, glass, metals, plastics, and asbestos are significant proportion of the globally generated solid waste. In urban areas, concrete waste accounts for a significant portion of solid waste. Concrete is prone to cracking, and when the cracks exceed a critical threshold, it adversely affects the concrete's durability and shortens its service life. Since it is not easy and efficient to recycle concrete components, concrete waste accumulates in landfills all over the world. In recent years, the use of bacteria to heal concrete cracks (bio concrete, biomineralization) has been investigated to increase the durability and service life of concrete structures and thus decrease the related waste generation. In this study we propose non-axenic microbial granules biogranules that can simultaneously conduct urea hydrolysis and nitrate reduction as a novel self-healing agent. Produced biogranules were harvested and their resuscitation performance after a drying process was tested. Upon confirmation of the resuscitation, dry granules were added to the mortar samples and their self-healing performances were monitored weekly under the microscope for crack widths varying between 25 mu m and 1000 mu m. Results indicated that the produced granules could be stored in dry form and can be resuscitated. The granules were able to consume 1 g/L of urea in 6 hours and 200 mg/L NO3-N in 3 hours. Enhanced crack healing performance was achieved for samples containing biogranules which was promising for increasing the service life of cementitious composites and for decreasing the construction waste generation.