A multi-scale observation including NMR, TGA, XRD, FITR, CT, MIP, and 1H NMR was conducted on ordinary Portland cement (OPC) and recycled cement (RC) with and without carbonation to examine the evolution of pore structures. The results indicated that a substantial portion of Q2 transformed into Q1 in RC. This change results in a decrease in the CSH aggregation degree and bonding strength between hydrated particles, consequently leading to an increase in CSH gel pores, small capillary pores, and voids. The increased pore volume in RC promotes faster CO2 penetration, thereby accelerating the carbonation process. This results in more efficient carbon capture compared to OPC. Thereby, CH and CSH in RC are more completely transformed than in OPC. Besides, both OPC and RC present a slight increase in compressive strength, and RC exhibits a more notable improvement in microhardness compared to OPC. RC proves to be an effective carbon-capture material, particularly due to its higher carbonation rate and porosity, enabling effective carbon sequestration while maintaining mechanical performance. This makes it suitable for use in non-structural components where steel corrosion is less of a concern, potentially revolutionizing sustainable construction practices. Considering the recycling process and carbon capture during service, compared to OPC paste, RC paste can reduce carbon emissions by 92.5 %.