Eco-Efficient LC3 Composites for Underwater 3D Printing in Digital Marine Construction

This study introduces the first application of limestone-calcined clay cement (LC3) for underwater 3D printing of structural elements, marking a significant step toward sustainable, low-carbon digital construction in submerged environments. In this work, ordinary Portland cement was partially replaced with 20%, 30%, and 40% LC3, composed of 70% calcined kaolinite-rich clay and 30% limestone. The composite is engineered to ensure printability, shape stability, and early strength development under water, using tailored rheology-modifying and anti-washout admixtures. A series of laboratory experiments evaluated the rheological performance, mechanical properties, long-term durability in acid–chloride environments, and microstructure of the printed elements. The LC3-modified mixes exhibited progressively higher yield stress, reaching »775 Pa at 40% replacement, alongside improved structural build-up. Compressive strength decreased with increasing LC3, with the 20% mix showing optimal mechanical balance. All LC3 blends retained over 87% of strength after 120 days of aggressive immersion. Altogether, these findings establish LC3-based composites as viable, eco-efficient solutions for underwater 3D printing. The proposed sustainable mix design, rheological control and durability verification lays the groundwork for practical marine infrastructure deployment.