A coral-reef-inspired eco-friendly foamed cement: Towards a sustainable alternative with high strength and water resistance

The development of foamed magnesium oxychloride cement (FMOC) offers a sustainable pathway for producing energy-efficient insulation materials with a lower environmental footprint. However, the pore structure and internal stress in traditional lightweight composites are prone to crack and collapse, which lead to a significant decline in their mechanical properties and water resistance. Corals can capture calcium carbonate from seawater by secreting specific organic substrates and deposit it layer by layer, which eventually forms a calcium carbonate skeleton that integrates hardness and toughness. Drawing inspiration from the biomineralization mechanism of coral reefs, this study introduces a method that provides an organic growth template and enables a dense organic-inorganic hybrid network by constructing a three-dimensional structure with alkali-treated rice straw (ARS) and carboxymethyl cellulose (CMC). In this system, the coordination interaction between CMC and Mg 2 + promotes the formation of a strong interfacial connection between hydration products and ARS, strengthening the compactness and structural integrity of the FMOC composites. Compared with unmodified FMOC, the 28-day compressive strength and softening coefficient of the FMOC/ARS/CMC-0.02 % composites increased from 2.00 MPa to 10.14 MPa and from 0.12 to 0.52, representing improvements of 407 % and 333 %, respectively. The flame-retardant performance of FMOC/ARS/CMC composites was significantly enhanced. Moreover, the post-combustion cracks of the modified FMOC composites were notably reduced, demonstrating excellent thermal stability and fire resistance. This research provides an effective approach for developing environmentally friendly, lightweight, high-strength, and flame-retardant FMOC composite building materials. • Coral-reef–inspired strategy enables high-performance organic–inorganic FMOC composites. • CMC forms a three-dimensional network with ARS, acting as an organic template. • The composite achieved a 28-day compressive strength of 10.14 MPa with a softening coefficient of 0.52. • Excellent flame retardancy and thermal stability enable promising applications in safe construction.