Enhancing freeze–thaw and high-temperature resistance of one-part alkali-activated slag foam concrete with waste concrete powder: role of curing conditions and fiber reinforcement

This study presents a mechanism-driven evaluation of one-part fiber-reinforced alkali-activated foam concrete (AAFC) incorporating waste concrete powder (WCP) and bottom ash (BA), with emphasis on curing conditions, freeze–thaw (F–T) durability, and high-temperature performance. Slag was partially replaced by WCP (10–50%), while polypropylene fibers (0–1%) enhanced matrix integrity. Increasing WCP reduced compressive strength due to lower reactivity and higher porosity; however, 1% fiber addition mitigated these losses, improving strength by up to 217% in high-WCP mixtures. Under F–T exposure, strength losses were limited to 26.15% (50 cycles) in optimized mixtures. High-temperature performance revealed superior thermal stability significantly improved residual strength retention up to 900 °C compared to fiber-free systems. While BA reduced density and thermal conductivity, it weakened interfacial bonding at high WCP levels. Optimum performance was achieved at 10–20% WCP with 1% fiber, highlighting the synergy between curing, fiber bridging, and pore structure.