Adaptive Mineralized Biochar Networks for Self-Healing Carbon-Negative Concrete in Coastal Infrastructure Systems

Abstract

Chinenye Elizabeth Onumadu

Introduction: Coastal concrete infrastructure faces accelerated degradation due to chloride-induced corrosion, cracking, and cyclic wet-dry exposure, leading to premature structural failure and exorbitant maintenance costs. Concurrently, cement production—a cornerstone of concrete—accounts for ~8% of global CO2 emissions, exacerbating climate change. While self-healing concrete technologies (e.g., bacterial calcite precipitation, encapsulated polymers) have emerged to mitigate cracking, they lack CO2 storage capabilities and perform poorly in high-salinity marine environments, leaving a critical gap in sustainable coastal construction. This study introduces adaptive mineralized biochar networks (AMBNs) as a multifunctional solution to these challenges. AMBNs were engineered by pyrolyzing rice husk biomass at 700°C, followed by CO2 activation and impregnation with Ca(OH)2 and MgCl2 to create reactive nucleation sites for CO2 trapping and carbonate precipitation. Concrete specimens with 3% cement replaced by AMBNs were pre-cracked to 300 μm and submerged in artificial seawater for 28 days to assess self-healing performance, durability, and CO2 sequestration.

Results: Results demonstrated that AMBNs achieved 78% crack closure for 300 μm cracks within 28 days, alongside a 22% reduction in chloride migration coefficient compared to control mixes. Thermogravimetric analysis (TGA) and direct carbonation tests revealed ~120 kg CO2 sequestered per tonne of concrete, while XRD and SEM-EDS confirmed healing products as biogenic calcite and aragonite, with no chloride interference. These findings highlight AMBNs’ unique ability to simultaneously enhance durability and carbon negativity in marine concrete.

Conclusion: In conclusion, adaptive mineralized biochar networks present a paradigm shift for coastal infrastructure, offering self-healing, chloride resistance, and CO2 storage in a single, scalable system. This innovation paves the way for carbon-negative, climate-resilient concrete in seawalls, breakwaters, and marine platforms, addressing both structural longevity and environmental sustainability.

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