The growing demand for sustainable construction materials has motivated the development of carbon negative concrete that can actively reduce atmospheric CO? levels. This study explores the use of algae-derived additives as a renewable and eco-friendly alternative to conventional supplementary cementitious materials. Microalgae biomass and its calcined derivatives were incorporated into concrete mixes to enhance carbon sequestration potential while maintaining structural performance. The experimental program investigated compressive strength, workability, and durability characteristics under varying replacement levels of cement with algae-derived additives. Results indicate that a 10�15% substitution can reduce the embodied carbon footprint by up to 25%, while also improving pore structure refinement and long-term durability. Moreover, the biogenic nature of algae enhances the self-healing ability of the concrete by providing additional reactive sites for carbonation. This research demonstrates the feasibility of algae-based additives as a promising pathway toward carbon negative concrete, thereby contributing to net-zero emission targets and advancing sustainable construction practice