Recycling recycled concrete powder into low-carbon construction material through compaction and carbonation

The recycling of concrete waste aggregate generates abundant recycled concrete powder (RCP) annually that remains underutilized. Previous studies have shown that the compaction-based recycling of concrete requires autoclave treatment to achieve sufficient strength, which consumes considerable energy. This study combined carbonation with compaction to recycle RCP into construction materials with low carbon emissions. The effects of variable aggregate content, compaction and carbonation on strength and interparticle bonding were investigated using several characterization techniques. Results showed that the compacted material had a compressive strength above 40 MPa without relying on hydration reactions. CaCO 3 grew on adjacent particles, became interconnected, and formed interparticle crystal bridges, shifting the mechanism of particle bonding from physical contact produced under pressure to chemical crystal bridge bonding. Both the pressure level and aggregate content exhibited a coupled effect on carbonation. CO 2 uptake offset the energy consumption of production, offering a low-carbon method for RCP recycling.