Geopolymeric subaqueous lightweight fill material derived by waste spoil in construction: Mechanical and microstructural analysis

This study presents a geopolymer-based Subaqueous Foamed Lightweight Soil (SFLS), innovatively facilitating the application of Foamed Lightweight Soil (FLS) for subaqueous backfilling and enabling waste spoil (WS) recycling on a large scale. Key findings include that modified SFLS with dispersants is suitable for subaqueous use, achieving over 90% of its 28-day unconfined compressive strength subaqueous compared to in air. SFLS offers advantages such as low wet density, excellent flowability, and adjustable strength (1-2 MPa). The synergistic interaction of geopolymers, Sodium Lauryl Ether Sulfate (SLES), and Polyacrylamide (PAM) enhances its performance, with the geopolymer reaction's alkaline environment improving fluidity and foam resilience. PAM's addition boosts dispersion resistance and foam stabilization, ensuring uniformity and lightweight benefits, thus fortifying SFLS's durability. With a density close to water, SFLS minimizes additional underwater stress, showcasing superior sustainability by significantly reducing costs and CO 2 emissions, indicating its potential for widespread application in sustainable construction practices. • Develop geopolymer-based subaqueous foamed lightweight fill for underwater use. • Achieve an excellent lightweight formula with fresh/mechanical properties. • Reveal the mechanism of stabilizing foam bubbles in geopolymeric slurry. • Derived by waste spoils in construction for solid waste utilization.