Development and Performance Evaluation of Microbially-formed Bio- Bricks incorporating Recycled Glass and Rocksand for Sustainable Energy-Efficient Construction

To address the environmental impact of traditional brick production and support sustainable construction practices, this study investigates the development of bio-bricks using Microbially Induced Calcium Carbonate Precipitation (MICP). The ureolytic bacterium Sporosarcina pasteurii was exploited to precipitate calcium carbonate, binding particles of locally extracted & produced rocksand and recycled glass obtained from waste glass streams within moulds designed to optimise fluid interaction. Various rocksand to recycled glass aggregate compositions (100:0, 80:20, 60:40, 40:60, 20:80 and 0:100) were tested to compare their mechanical, thermal, and water absorption properties. A delayed onset of MICP was observed, and this was attributed to suboptimal temperature and media conditions for the growth of S.pasteurii . Bio-bricks displayed compressive strengths ranging from 0.397 to 1.62 MPa and thermal conductivity values between 0.2174 and 0.4168 W/mK. Compressive strengths of bio-bricks were inferior to those of commercial bricks, but their thermal performance was superior, indicating their suitability for non-load-bearing, thermally insulating applications. Water absorption ranged from 19.46% to 34.28%, indicating incomplete cementation. Scanning Electron Microscopy and calcium carbonate content mapping revealed heterogeneous crystal distribution, influenced by aggregate type and reactor flow dynamics. Efficient MICP could be achieved via controlled temperature (~ 30°C) and appropriate fluid flow, with samples in proximity to the pump exhibiting a more uniform calcium carbonate precipitation compared to those further away, highlighting the importance of reactor dynamics for uniform bio-brick formation. Simulation results confirmed improved indoor thermal comfort and reduced energy demand when using the bio-bricks in construction. This study highlights the potential of MICP-treated materials as eco-friendly building alternatives aligned with Sustainable Development Goals.