Enhancing mechanical, durability, and microstructural performance of fly ash-based one-part geopolymer foam concretes using marine mucilage and polypropylene fibers

This study presents a bio-circular approach for valorizing marine mucilage (MM), an emerging marine pollutant, in sustainable one-part geopolymer foam concretes (GFCs). Fly ash (FA) was used as the primary binder, MM replaced silica sand (SS, 0–50%), and polypropylene fibers (PPF, 0–2%) were incorporated. MM-PPF synergy enhanced matrix densification: compressive strength increased from 2.46 to 5.64 MPa (≈129%) and flexural strength from 0.54 to 1.43 MPa (≈165%). Sorptivity decreased from 30.3 to 11.6 kg/m2 (≈62%), indicating refined pore structure, while thermal conductivity rose moderately (0.31–0.46 W/m•K), maintaining lightweight insulation. Durability improved markedly, with >60% strength retention at 800 °C, <20% loss after 50 freeze–thaw cycles, and ≈10% mass loss under acid attack. Microstructural analysis confirmed improved gel continuity, pore refinement, and crack-bridging mechanisms. MM-PPF-modified GFCs provide an eco-efficient, low-carbon alternative with strong potential for sustainable cement-based construction materials.