Investigation on the influence of chelating agent on carbon sequestration in cement-based materials

The incorporation of a chelating agent significantly enhances the mineralization reaction in cement-based materials during carbonation curing, thereby increasing CO₂ sequestration efficiency and contributing to a measurable reduction in net CO₂ emissions. This study systematically investigates the effects of adding a specific dosage of chelating agent to cement paste and concrete under carbonation curing, with emphasis on mineralization behavior, microstructural evolution, mechanical performance, durability-related properties, and self-healing capability. The mineralization products and carbonation mechanisms were analyzed using XRD and TG–DSC, while the influence of the chelating agent on the microstructure, mechanical properties, permeability, pore size distribution, and ultrasonic response of concrete was comprehensively evaluated. The results demonstrate that the chelating agent promotes CaCO 3 formation, refines the pore structure, and enhances matrix compactness, leading to improved carbonation efficiency, mechanical performance, and durability. Enhanced resistance to chloride penetration and superior crack self-healing behavior were also observed in the chelating agent–modified concrete. Quantitatively, under accelerated carbonation conditions (98% CO₂, 0.2 MPa, 48 h), cement paste containing 0.5 wt.% chelating agent achieved a carbonation rate of 42.5%, which is 7.6% higher than that of the control sample. For concrete cured at 20% CO₂, 20 °C, and 70% relative humidity for 28 days, the chelating agent–modified specimen sequestered CO₂ equivalent to 18.3% of the cement mass, corresponding to an estimated net CO₂ emission reduction of approximately 12.7 kg CO₂ per ton of concrete compared with the unmodified concrete. After 28 days of CO₂ curing, the compressive strength, chloride diffusion coefficient, and maximum ultrasonic amplitude of the modified concrete reached 43.5 MPa, 5.64 × 10⁻¹² m²/s, and 173.66 mV, respectively. Moreover, the chelating agent endows concrete with excellent self-healing capability for cracks. Generally, the chelating agent plays a beneficial role in the carbonation curing of cement-based materials, offering positive applications for enhancing durability and CO₂ sequestration.