Ultrafast underwater self-sustaining manufacturing of polymer concrete driven by frontal polymerization

FP drives underwater 3D printing of polymer concrete, avoiding thermal quenching. • Achieves formwork-free subaqueous construction and rapid in-situ solidification. • 3% cement triggers robust organic-inorganic synergy via Ca O and hydrogen bonds. • Lightweight concrete (0.83 g cm −3 ) instantly attains 16 MPa compressive strength. In time-critical marine engineering, structural materials require instantaneous prototyping and immediate load-bearing capabilities. However, traditional concretes suffer from sluggish hydration, while traditional thermal bulk curing and photopolymerization suffer from limitations such as low efficiency and restricted auxiliary means. Herein, grounded in organic/inorganic composite regulation, we propose an underwater 3D printing technology for polymer concrete driven by frontal polymerization (FP) compared to traditional marine construction materials. By tailoring thermo-chemical kinetics, the slurry overcomes aquatic heat dissipation, maintaining a 65 mm min −1 self-propagating wavefront and achieving formwork-free solidification within 41 s. Crucially, incorporating 3% sulphoaluminate cement fundamentally reshapes long-term underwater durability. Molecular dynamics and X-ray computed tomography (CT) reveal that cement hydration products establish robust multiscale interfacial anchoring via Ca O coordination and hydrogen bonds, creating a highly tortuous pore topology that physically obstructs water ingress. Consequently, this lightweight composite (0.83 g cm −3 ) rapidly attains a 16 MPa instant compressive strength and exhibits progressive mechanical enhancement over a 28-d immersion period, offering a self-sustaining paradigm for underwater construction.