The increasing emphasis on sustainable and energy-efficient construction materials has heightened interest in structural lightweight concrete (LWC) due to its potential to reduce dead load and enhance thermal performance. Conventional concrete, with a density of around 2400 kg/m³, contributes substantially to the self-weight of structures, whereas incorporating lightweight aggregates can lower density by nearly 20 %. Polyurethane-foam (PUF) concrete, with densities between 1700 and 1950 kg/m³, offers significant weight reduction but suffers from brittleness and reduced strength caused by interconnected voids. To overcome these limitations, this study integrates polypropylene (PP) fibers into PUF concrete, leveraging their high tensile strength, corrosion resistance, and economic viability. Six mixes were prepared by varying foam content (10 % and 15 %) and PP fiber dosage (0–1 %). Mechanical, durability, and microstructural properties were evaluated. The optimal mix containing 10 % foam and 1 % fiber achieved a 25 % reduction in dry density, 30 % improvement in compressive strength, and 29 % decline in chloride permeability. Microstructural analysis revealed compact calcium–silicate–hydrate (C–S–H) gel formation around intact fibers. The findings demonstrate that PP-fiber-reinforced PUF concrete effectively combines lightweight characteristics, mechanical strength, and durability suitable for sustainable structural applications.
