Bio-Cemented Concrete with Industrial By-Products for Low-Carbon Urban Infrastructure

Abstract

The construction industry faces increasing pressure to reduce the environmental impacts associated with Ordinary Portland Cement (OPC) production while maintaining the performance requirements of modern infrastructure. This study investigated the feasibility of producing low-carbon bio-cemented concrete through the combined use of Fly Ash, Ground Granulated Blast Furnace Slag (GGBS), and Sporosarcina pasteurii-induced microbial calcite precipitation. Four concrete mixtures, consisting of a conventional OPC control and three bio-cemented variants, were evaluated through mechanical, durability, microstructural, and environmental assessments. The results showed that the hybrid mixture (BIO-HYB) achieved the highest 28-day compressive strength of 46.8 MPa, exceeding the control concrete (38.2 MPa) by approximately 22.5%. BIO-HYB also exhibited superior tensile strength (4.15 MPa), flexural strength (6.22 MPa), durability index (14.95), and chloride resistance (640 Coulombs). Water permeability was reduced from 4.25 × 10⁻¹² m/s in the control mixture to 0.88 × 10⁻¹² m/s, indicating substantial pore refinement. SEM observations confirmed extensive calcite deposition within pores and microcracks, resulting in a denser internal structure. Furthermore, embodied carbon decreased from 385.0 to 121.2 kg CO₂-eq/m³, corresponding to a 68.52% reduction in Global Warming Potential. The novelty of this study lies in integrating microbial calcite precipitation with dual industrial by-product substitution using Fly Ash and GGBS within a structural concrete system while simultaneously evaluating its engineering and environmental performance. The findings demonstrate that hybrid bio-cemented concrete offers a promising pathway toward high-performance and low-carbon urban infrastructure.