Microbial calcium carbonate precipitation with high affinity to fill the concrete pore space: nanobiotechnological...

Despite the advantages of concrete, it has a pore structure and is susceptible to cracking. The initiated cracks as well as pores and their connectivity accelerate the structure degradation by permitting aggressive substances to flow into the concrete matrix. This phenomenon results in a considerable repair and maintenance costs and decreases the concrete lifespan. In recent years, biotechnological approach through immobilization of bacteria in/or protective vehicles has emerged as a viable solution to address this issue. However, the addition of macro- or micro scale size particles can decrease the integrity of matrix. In this study, the immobilization of bacteria with magnetic iron oxide nanoparticle (ION) was proposed to protect the bacterial cell and evaluate their effect on healing the concrete pore space. The results show that the addition of immobilized bacteria with IONs resulted in a lower water absorption and volume of permeable pore space. Crystal analysis using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) revealed that CaCO₃ was precipitated in bio-concrete specimen as a result of microbial biosynthesis.