Biochar-amended engineered cementitious composites

This study investigates the incorporation of biochar as a sustainable cement replacement in high-strength ECC, focusing on mechanical properties, durability, microstructural characteristics, and environmental impacts. Biochar was added at 5%, 10%, 20%, and 30% replacement levels by cement weight, and its effects were assessed through compressive and tensile strength tests, TGA, SEM, and LCA. Results showed that biochar-enhanced ECC achieved 28-day compressive strengths of 95.4–99.6 MPa, with a peak tensile strength of 8.58 MPa at 20% biochar content, though higher dosages reduced strain capacity. TGA confirmed increased pozzolanic activity with reduced portlandite content, while SEM images revealed a denser ITZ at 5–10% biochar, enhancing fiber-matrix bonding. Although higher biochar levels increased water sorptivity and gas permeability, drying shrinkage was reduced by up to 24%. LCA results indicated an 80% reduction in carbon emissions, with biochar sequestering 2.0 kg CO₂-eq per kg. These findings highlight biochar-amended ECC as a promising solution for sustainable construction, balancing mechanical performance and environmental benefits.