Abstract: Against the backdrop of rapid advancements in building energy efficiency and green building practices, existing research on life-cycle carbon emissions predominantly focuses on conventional building materials and specific case studies. There remains a significant lack of systematic research on the carbon emissions associated with construction waste recycling and reuse, particularly for recycled concrete. Quantitative patterns under varying substitution rates and transportation distances are still largely unexplored. This paper establishes life-cycle carbon emission models for recycled aggregate concrete (RAC), recycled lump concrete (RLC), and recycled aggregate-recycled lump concrete (RLAC) based on a carbon emission inventory covering four stages: material production, transportation, construction, and demolition. By setting multiple parameter scenarios, including substitution rates of recycled aggregates and recycled lumps, as well as transportation distances, a sensitivity analysis is conducted. Cross-comparisons with concrete of different strength grades are performed to systematically reveal the quantitative relationships between substitution rates, transportation distances, and carbon emissions. The carbon emission reduction rate of RAC is higher than that of RLC but lower than that of RLAC. The carbon emission reduction rates of RAC, RLC, and RLAC decrease as the concrete strength grade increases, and the magnitude of reduction diminishes with higher strength grades. Additionally, the carbon emission reduction rates of RAC, RLC, and RLAC decrease as the transportation distances for recycled lumps and recycled aggregates increase. The carbon emissions of recycled concrete are jointly influenced by substitution rates and transportation distances, exhibiting a distinct threshold effect. Optimizing the synergistic use of recycled aggregates and recycled lumps while rationally controlling transportation distances can maximize life-cycle carbon reduction benefits. This study provides replicable technical pathways and data support for policy-making and engineering applications in building energy efficiency and green building initiatives.