Innovative Use of Carbonated Calcium-Rich Materials in Concrete: Blended Paste Development

This study proposes a novel three-step solution for incorporating mineral carbonation into fresh concrete. With lime and partially hydrated ordinary portland cement (OPC) as calcium-rich materials (CRMs), the method involves CO2 injection into CRM slurries, followed by powdering of the carbonated products, and finally, integration of these powders into concrete mixtures. This study focuses on developing and characterizing carbonated CRMs, analyzing their impact on the heat of hydration, strength, and microstructure of cement paste. Calcite was identified as the dominant component in the carbonated CRMs, as evidenced by distinct calcite peaks in thermogravimetric analysis (TGA) profiles, X-Ray diffraction (XRD) spectra, and morphology changes noted in scanning electron microscopy. At OPC replacement of up to 15%, carbonated CRMs preserved hydration products, as confirmed by TGA and XRD, and contributed to enhanced early age strength, maintaining over 95% compressive strength at 28 days. These findings suggest that the proposed carbon utilization method offers a sustainable solution for concrete production.