Cement production contributes 8 % of global industrial carbon emissions, underscoring the urgent need for innovative strategies to mitigate its environmental impact. Super Sulfated Cement (SSC) is a promising low-carbon alternative, but its carbon sequestration potential remains underexplored. This study integrates biochar and zeolite into SSC to create a near-zero-carbon, high-performance composite with hierarchical transport pathways, enhancing compressive and flexural strength by 63.1 % and 43.8 %. A comprehensive mechanism for the composite's carbon sequestration is proposed, leveraging biochar's tunnel-like channels and zeolite's nano-pores, along with molecular sieve properties, to create a hierarchical pore structure. This structure facilitates CO₂ transmission to greater depths and enables lateral diffusion, increasing carbonation by 37 % and CO₂ uptake to 41.7 kg·CO₂/kg. Its Global Warming Potential is 51.08 kg·CO₂/kg, reducing emissions by 87 % and 51.1 % compared to Ordinary Portland Cement (OPC) and SSC, respectively. This study provides an innovative, scalable pathway to developing ultra-low-carbon cementitious materials, leveraging industrial and agricultural waste to enhance environmental sustainability. The findings offer actionable insights for advancing carbon capture technologies and achieving negative-carbon cement production. Synopsis: Integrating biochar and zeolite into supersulfated cement enhances CO₂ sequestration, reducing lifecycle carbon emissions and addressing solid waste valorization and air quality challenges.

To alleviate the excessive extraction from natural resources and to properly manage construction waste, recycled concrete technology is globally recognized as an eco-friendly way to address these escalating challenges. This study explores the influence of three particle size distributions (PSD) (upper, median, and lower limits) and two curing conditions (normal: 19–25 °C, humidity 48–56 %; lab standard: 20 ± 2 °C, humidity ≥ 95 %) on the compressive strength, tensile splitting strength, and strength development of recycled concrete through a series of experiments. The detailed data make up the research gap in this aspect and reveal that the influence of the PSD on the compressive strength and tensile splitting strength is limited. However, a favourable curing condition benefits the mechanical properties of recycled concrete, especially in resisting tension. In terms of compressive strength, this study indicates that recycled concrete has the potential to replace natural aggregates totally and is feasible to be applied in almost all practical engineering applications, which provides a solid foundation for the future of sustainable construction.