Performance-oriented mix design of low-carbon concrete with manufactured aggregate for enhanced durability

Reducing embodied carbon without sacrificing strength and durability remains a key challenge in concrete mix design. This study develops a performance-oriented mix-design framework for concrete with manufactured aggregate. The framework integrates aggregate packing optimization and nominal paste film thickness control. Equivalent water-to-binder ratio regulation and high-volume supplementary cementitious materials are incorporated within the same design procedure. Compared with an engineering reference mixture, the designed mixtures increased the 28 d compressive strength by 33.9%–52.0% and reduced carbon emissions by 32.0%–40.8%, while showing consistently improved durability in terms of chloride penetration, carbonation, drying shrinkage, and freeze–thaw resistance. Mercury intrusion porosimetry (MIP) revealed pronounced paste-scale pore refinement in the low-clinker binder system. Backscattered-electron imaging (BSE) and nanoindentation further showed differences in concrete-scale microstructure and local mechanical response near aggregate–paste interfaces. These results demonstrate that the integrated design strategy can improve mechanical and durability performance while reducing embodied carbon within the investigated material system. Among the mixtures investigated, a nominal paste film thickness of 20 μm and an equivalent water-to-binder ratio of 0.70 provided a favorable balance among strength, durability, and carbon emissions. The proposed framework provides a practical approach for performance-oriented design of low-carbon concrete with manufactured aggregate.