Abstract: Foamed concrete faces challenges in ultralight design and functionalization due to poor foam stability, which causes defective pore structures. This study innovatively utilized cocamidopropyl betaine (CAB) to induce self-assembled sodium stearate (SS) in aqueous solutions, forming a three-dimensional nanofiber network. Foam stability tests, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) characterization confirm that the three-dimensional nanofiber network significantly enhances liquid film strength and system viscoelasticity, achieves an ultra-stable foam with about 2.10% volume loss over 120 h and a reduced average bubble diameter of 12.22 μm at 2.00% (mass fraction) SS nanofiber concentration. Using this foam as a template, ultralight foamed concrete with a density of 60 kg/m³ is successfully prepared, exhibiting a low thermal conductivity of 0.056 W/(m·K)—a 52.14% reduction compared to conventional 200 kg/m³ foamed concrete—with a superior insulation property confirmed by thermal imaging. Compression tests reveal that the foamed concrete material exhibits a polymer-like foam densification behavior. The compressive strength decreases with the decrease of density (0.012 MPa at a density of 60 kg/m³). However, the nanofiber network enhances mechanical response by suppressing crack propagation. Fire resistance testing (1 000 ℃ flame burning for 2 min) demonstrates the formation of a sintered protective layer on the surface of the foamed concrete specimen, accompanied by ~10% volume shrinkage. This work proposes an industrially viable integrated strategy combining foam stabilization and multifunctionalization to develop foamed concrete with ultralight, thermal insulation, and fire resistance.

Key words: nanofiber, ultra-stable foam, foamed concrete, mechanical property, thermal insulation performance, fire resistance performance