Balancing Workability, Buildability, and Carbon Sequestration in 3D Printed Concrete via Direct CO2 Mineralization (2026-01)¶

This study investigates the influence of direct CO2 injection during mixing on the fresh, mechanical, and buildability properties of 3D-printed concrete, aiming to support both sustainable construction practices and carbon capture, utilization, and storage (CCUS). Six mixtures containing 0–5% CO2 by mass were evaluated for slump flow, open time, heat of hydration, compressive strength, drying shrinkage, and printing performance. Results show that CO2 incorporation accelerates hydration, shortens open time, and reduces flowability, with reductions becoming significant beyond 2% CO2. Early-age compressive strength (1–7 days) increased by up to 26%, but excessive CO2 (>3%) hindered long-term strength development. Drying shrinkage increased proportionally with CO2 content. Printing trials demonstrated that moderate CO2 dosages (1–2%) improved geometric stability and interlayer bonding, while excessive contents caused premature stiffening and extrusion defects. An optimal CO2 range of 1–2% was identified to balance workability, buildability, and CO2 sequestration efficiency, providing a practical pathway toward low-carbon 3D concrete printing.