Sustainable and strength-enhanced concrete using microbial consortia

Abstract

The mechanical properties of concrete were examined by using steel fibres and two types of bacteria (Pseudomonas otitidis and Bacillus cereus). These steel fibres and bacteria were incorporated into the concrete mix in proportion to the weight of the cement. To ensure the resilience of microbial consortia incorporated into bio-concrete against the mechanical and chemical stresses encountered during concrete production, these microorganisms should exhibit critical characteristics, including robust alkali resistance and the ability to produce endospores. By employing 16S rRNA gene sequencing, we verified the identity of a group of organisms isolated from fermented lime mortar and curing construction water. Microbiologically induced calcite precipitation (MICP) was confirmed through microstructural analyses using techniques such as scanning electron microscope (SEM) and x-ray diffraction (XRD). The concrete was prepared with optimal concentrations of cultured bacteria (ranging from 10³, 10⁵ and 10⁷ cells/ml), and steel fibres were added to the concrete at varying percentages (0%, 1%, 1.5%, and 2%). The optimal steel fibre content was 1.5%, and its strength properties were compared to conventional concrete. Notably, when Pseudomonas otitidis and Bacillus cereus bacteria were added to the traditional and optimal concrete mix, the compressive strength was significantly enhanced compared to the conventional concrete mix.