Work

Effect of carbonation pressure on the chloride ion transport and redistribution in Portland cement pastes

Year: 2025

Type: article

Abstract: Durability of reinforced concrete in marine environments is severely compromised by coupled effects of carbonation and chloride ingress, particularly under pressurized CO 2 conditions, as deep-sea engineering structures and performance enhancement of chloride-containing recycled aggregates. This study examines the influence of carbonation pressure (0–200 kPa) and chloride doping (0–0.36 % Cl⁻) in hardened cement paste. A combination of mercury intrusion porosimetry (MIP), microhardness measurements, and potentiometric titration was employed to investigate the microstructure evolution, chloride redistribution, and carbonation front progression. Results show that elevated CO 2 pressure produces dense calcium carbonate layers that increase surface density while restricting deeper penetration. Pressurization stabilizes internal relative humidity (∼70 %–80 %), shifting CO 2 transport from gas-phase diffusion to liquid-phase convection. Microcracking and amplifying ionic gradients generated by pressurized carbonation drive the inward transport of Cl⁻. Residual chlorides present long-term risks, with concentrations at corrosion-critical thresholds (∼0.30 %) persisting beyond 20 mm depth. The study addresses key limitations in current durability predictions for coastal infrastructure, and enhance the application of high-pressure CO 2 in the construction industry.

Source: Case Studies in Construction Materials

DOI: 10.1016/j.cscm.2025.e05640