Sustainable Construction of Building Envelopes Using Basalt Fiber-Reinforced Rubberized Concrete: The Case of Jordan

This study evaluates basalt fiber-reinforced rubberized concrete for building envelopes in Jordan’s hot, dry climate. Two mixes with 6% rubber and 0.5% basalt fibers (M1) or 0.8% basalt fibers (M2) were compared with a reference. Rubber reduced density by 1.0–2.2% but increased absorption by 9.7–24.7% and porosity by 8.7–22.1%. Fibers improved tensile strength by 14–26% and flexural strength by 23–35%, promoting ductile failure. Thermal conductivity decreased by 13.0% (M1) and 4.3% (M2); CTE increased by 10.8% (M1) and 2.0% (M2). M1 achieved the lowest annual energy consumption (0.15–0.28% reduction, with >95% simulation robustness). While material-level thermal improvements are confirmed, they do not translate proportionally into building-scale savings because insulation layers dominate the overall thermal resistance. Tensile enhancements exceeded additive predictions; however, this interpretation is limited by the absence of rubber-only and fiber-only control mixtures and direct microstructural evidence. Therefore, synergy is presented solely as a hypothesis requiring verification through a full factorial experimental design and microstructural investigation. Both materials suit non-load-bearing Jordanian envelopes, with mass-based replacement enabling direct technology transfer. The materials represent a potentially more sustainable option for envelope applications, though long-term durability validation and comprehensive lifecycle assessment are urgently needed. The findings are strongly connected with Jordanian conditions, and direct generalization to other regions is limited and should be stated explicitly.