Enhancing interlayer bonding in 3-dimensional printed concrete using bacteria-based biomineralization

Microbially induced calcium carbonate precipitation (MICCP) has demonstrated considerable promise in enhancing the mechanical properties and durability of 3D printed concrete (3DPC). This study aims to assess the on-site applicability of a ready-to-use, fly ash-based bacterial inoculum designed for industrial use, with the objective of enhancing interlayer cohesion while reducing environmental impact. A comprehensive testing regime was conducted, encompassing direct and splitting tensile tests, in conjunction with microstructural analyses, including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FT-IR), 3D Digital Image Correlation (3D DIC), and Mercury Intrusion Porosimetry (MIP). The testing was conducted across two series of specimens. The findings indicate that the incorporation of nutrient broth (NB) supplemented with nutrients during the printing and curing process led to a substantial enhancement in mechanical performance. Specimens treated NB and cured NB-enriched water showed an increase in splitting tensile strength and direct tensile strength of 422.21 % in Series I and 509.25 % in Series II. Further analysis via SEM revealed the formation of lamellar rhombohedral calcite crystals (3–7 μm), and XRD confirmed greater calcite content in NB-treated specimens. TGA results indicated increased calcite formation, while MIP analysis revealed reduced porosity and more refined pore structures in treated specimens. These findings confirm the effectiveness of MICCP using a field-deployable bacterial solution, paving the way for scalable applications in sustainable 3D concrete printing. Future studies should investigate further optimization for field deployment and adaptation of bacterial strains to varying environmental conditions.