Optimized biochar and SCMs for improved mechanical properties and sustainability of engineered/strain-hardening cementitious composites (ECC/SHCC)

Engineered Cementitious Composites (ECC) exhibit excellent ductility and crack resistance but rely heavily on cement consumption, limiting their environmental and economic sustainability. This study systematically investigates the integration of biochar and supplementary cementitious materials (SCMs) into ECC formulations, with a focus on optimizing mechanical performance, life cycle environmental impacts, and cost efficiency. The findings demonstrate that a strategic combination of high fly ash content and moderate biochar incorporation not only maintains, but can enhance, the functional properties of ECC while substantially reducing its carbon footprint. Excessive biochar reduces strength and crack control, emphasizing the importance of dosage optimization. Scenario analysis further reveals that biochar production method significantly influences environmental outcomes, with gasifier-based systems outperforming traditional pyrolysis. As compared to alternatives with ground granulated blast furnace slag and low-fly ash, the high-FA ECC mixes with controlled biochar incorporation present a viable pathway toward sustainable cementitious composites. This study offers a performance-based framework to guide ECC mix design under life cycle and carbon reduction considerations, underscoring the importance of dosage optimization and production method selection in realizing the full potential of biochar as a sustainability additive in cementitious composites.