Synergistic enhancement of mechanical, thermal, and durability properties in expanded perlite‐based lightweight alkali‐activated composites with basalt fiber and natural zeolite

Abstract This study investigates the development and performance optimization of lightweight alkali‐activated composites (AALCs) incorporating 100% expanded perlite (EP) as aggregate and basalt fibers (BF) as reinforcement. Ground granulated blast furnace slag (GBFS) was used as the primary binder, partially replaced by natural zeolite (NZ) at 0%, 15%, and 30%. Sodium silicate and sodium hydroxide were employed as activators, and thermal curing was applied at 40 and 80°C for 8 h. A comprehensive evaluation of mechanical, physical, and durability properties was performed, including compressive and flexural strength, porosity, water absorption, sorptivity, and resistance to sulfate, freeze–thaw, and high‐temperature exposures. The optimal performance was achieved in the 0% NZ–0.6% BF mixture cured at 80°C, which attained a compressive strength of 15.36 MPa, flexural strength of 1.15 MPa. The partial replacement of GBFS with NZ, combined with the incorporation of BF, significantly enhanced the sulfate resistance of AALCs. In particular, the mixture containing 30% NZ and 0.6% BF exhibited the lowest compressive strength losses‐13.2% and 15.7%‐after sulfate exposure under curing conditions of 40 and 80°C, respectively. Similarly, the synergistic effect of NZ and BF also contributed to improved freeze–thaw resistance. Among the mixtures cured at 40°C, the combination of 30% NZ and 0.6% BF resulted in the lowest strength loss. Under elevated curing at 80°C, the optimum freeze–thaw resistance was observed in the mixture with 0% NZ and 0.3% BF. The mixtures cured at 80°C and incorporating both NZ and BF exhibited superior high‐temperature resistance. Among all formulations, the mixture containing 0.3% BF and 0% NZ showed the lowest compressive strength loss following exposure to 600°C. These findings demonstrate that the synergy between highly reactive GBFS, optimal fiber content, and elevated curing temperature enables the production of lightweight, mechanically robust, and durable AALCs suitable for use in aggressive environments, despite the high porosity of the EP aggregate. From a practical perspective, the optimized AALC formulations present a promising alternative for lightweight structural and thermally efficient construction materials. Their combination of high durability, low density, and reduced water absorption makes them particularly suitable for façade panels, insulation blocks, and precast components exposed to harsh climatic or chemical conditions. Thus, the proposed mix design provides a sustainable pathway for replacing conventional Portland cement‐based systems in applications demanding both structural reliability and environmental efficiency.