Experimental Study of the Microstructural Characterization of Microbial Induced Calcite Precipitation (MICP) Bio-Cement Concrete

Microbial-induced carbonate precipitation (MICP), a bio mineralization technology facilitated by bacteria, has been a prominent research topic for scientists and engineers over the past few years as a multidisciplinary method. In the present study a MICP was studied using bio-cement solution in conventional concrete, enhancing its performance without adding extra cement. Tests on workability, compressive strength, splitting strength, flexural strength, water absorption, and permeability were conducted. The results revealed that 60% bio-cement improved compressive strength, tensile strength, flexural strength, and permeability depth by 33.7%, 12.4%, 12.4%, and 46.7%, respectively. To justify the improvement, the internal structure of concrete was studied at microscopic level through Scanning Electron Microscopy (SEM), X-ray Diffraction Analysis (XRD), and Fourier Transformed Infrared Spectroscopy (FTIR). These tests provided valuable insights into the composition and properties of bio-cement concrete, which can be used to evaluate its performance and durability. SEM analysis showed that the addition of 60% bio-cement solution enhances the microstructure of concrete, resulting in fewer and smaller cracks, a denser Interfacial Transition Zone (ITZ), a homogeneous distribution of active and inactive concrete ingredients, and reduced pore voids. Furthermore, XRD and FTIR analyses indicated that integrating 60% MICP bio-cement into the concrete mix facilitates the formation of essential components, such as calcium silicate hydrate (C–S–H) gel, Silica (quartz), calcium aluminosilicate hydrate (C–A–S–H), calcite (CaCO₃), portlandite, and ettringite. From the study it was concluded that, the microstructural tests with 60% bio-cement solution exhibits fewer air voids, and greater structural integrity. Therefore, a 60% bio-cement solution is optimal, enhancing the compressive strength, splitting tensile strength, flexural strength, and durability properties of the conventional concrete.