Biochar demonstrates strong potential as a supplementary cementitious material in concrete but significantly affects workability when added by weight. To address this, this study applied a volumetric water-to-cementitious materials ratio (w/c), replacing cement with biochar powder by volume at 5 %, 10 %, and 20 %, and compared the results to a 5 % weight-based replacement. Additionally, biochar aggregate was used to replace sand at 30 %, 60 %, and 100 % by volume, offering a sustainable solution to ecological degradation and environmental pollution. Various properties, including slump, air content, mechanical strength, and hydration products, were assessed. For biochar powder replacing cement, the results indicate that the volumetric w/c ratio effectively improved workability and enhanced internal curing, leading to increased hydration products and better mechanical performance compared to weight-based biochar replacement. Despite having a lower cement content, the 10 % volumetric biochar sample achieved higher strength than the 5 % weight-based sample. Furthermore, replacing sand with biochar aggregate reduced shrinkage through internal curing. However, due to its poor engineering properties, excessive sand replacement negatively impacted concrete strength, suggesting that biochar aggregate replacement should not exceed 30 %.