Carbon dioxide capture and sequestration in cement-based materials incorporating superabsorbent polymers: Mechanical properties and microstructural analysis

To mitigate carbon dioxide (CO₂) emissions caused by the construction industry, we investigated the CO₂ capture and sequestration performance of cement-based materials with an incorporated superabsorbent polymer (SAP) by evaluating their mechanical properties and microstructural characteristics. For this purpose, specimens were initially cured under standard conditions for 7 days. Subsequently, one group was subjected to additional air curing and the other to additional CO₂ curing. Compressive strength, flexural strength, and carbonation depth were measured and accompanying microstructural changes were examined. The results demonstrate that SAP incorporation influenced carbonation behavior, with larger particle sizes and higher dosages promoting more extensive carbonation reactions. After CO₂ curing, the compressive and flexural strengths of the material at 28 days increased by up to 6.9 % and 4.0 %, respectively, compared to the reference specimen whereas these two factors were reduced by air curing. Microstructural analysis confirmed that calcium carbonate (CC‾) precipitation increased significantly with greater SAP content and material particle size, which was subsequently reflected in the surface fractal dimension and tortuosity. Notably, a specimen containing 0.5 wt% SAP with a median particle diameter of 594 μm exhibited more than double the CO₂ capture efficiency relative to the reference specimen. These experimental results support the hypothesis that SAP voids formed through the absorption and release of mixing water and accompanied by internal compositional changes provide preferential sites for CO₂ ingress and retention. This promotes reactions with Ca²⁺ ions and facilitates CO₂ sequestration in the form of CC‾ while contributing to microstructural densification. Taken together, these findings highlight that the ability to tailor SAP-induced pore structures through particle-size control, combined with SAP's inherent internal curing and self-healing capabilities, offers a distinctive and material-integrated CO₂ sequestration pathway that complements conventional approaches.