Regenerative hydrogel-based living microbial mortars: investigation of viability and strength in successive material generations
Over the past 20 years, considerable research efforts have been aimed at improving properties of cement-based materials using microbial-induced calcium carbonate precipitation (MICCP). Generally, it has been shown that MICCP can reduce permeability and increase compressive strength in these systems by filling pores and sealing microcracks. Previous studies have also interrogated the potential for embedded microorganisms to survive long-term and promote crack-sealing in situ during the material’s service life with some success; however, it is known that the long-term viability of microorganisms in cement-based systems is threatened by harsh environmental conditions that are intrinsic to ordinary portland cement (OPC) concrete, including high pH, elevated temperature during hydration, and nutrient depletion. In this study, Synechococcus sp. PCC 7002, a cyanobacterium capable of MICCP, was used to create a cement-free, hydrogel-based “living” mortar. These mortars were examined for their microstructural properties, cell viability, and propensity to regenerate when subjected to temperature gradients. Scanning electron microscopy revealed that the bio-based hydrogel acted both as the primary binding agent and as a scaffold for microbial activity. Results suggested that these hydrogel-based microbial mortars generally exhibited greater property tunability and more favorable environmental conditions for beneficial microbial activity and viability than has been observed in cement-based mortars.