Abstract

In hot climates, efficient thermal management of buildings is critical for reducing energy consumption. Conventional cementitious materials exhibit low thermal conductivity, limiting heat dissipation, whereas geopolymers, as sustainable alternatives to Portland cement, offer the potential for enhanced heat transfer when modified with conductive fillers. This study investigates the effect of Fe and Cu powders on the properties of fly ash-based geopolymers to develop multifunctional materials capable of mitigating indoor overheating. Geopolymers containing 0–20 wt% metallic fillers were prepared under controlled curing conditions. Thermal performance was evaluated using flame-induced heating and ice-assisted cooling tests, while compressive strength tests assessed the mechanical response. Results show that metallic fillers markedly enhanced heat transfer: thermal conductivity increased from 1.31 W m⁻¹ K⁻¹ in the control to 2.44 W m⁻¹ K⁻¹ for 20 wt% Fe and 3.52 W m⁻¹ K⁻¹ for 20 wt% Cu. Opposite-surface temperatures during cooling decreased from 30 °C to 21 °C and 18 °C for Fe– and Cu–filled geopolymers within 10 min, respectively, with higher filler contents accelerating the cooling response. SEM–EDX studies confirmed a reduced porosity and dense well–bonded gel, creating continuous thermal pathways. Compressive strength increased by up to 1.5 times compared to the control, confirming that metallic incorporation enhances mechanical performance alongside thermal conductivity. Therefore, metal-powder-filled geopolymers provide a dual benefit of efficient cooling and structural robustness. These composites are promising for passive cooling applications in building envelopes, offering a sustainable strategy to lower indoor temperatures, reduce air–conditioning demand, and advance energy–efficient construction in hot climates.