Utilizing waste materials to produce sustainable concrete has substantial environmental implications. Furthermore, understanding the exceptional durability performance of ultra-high-performance concrete can minimize environmental impacts and retrofitting costs associated with structures. This study presents a systematic experimental investigation of eco-friendly ultra-high-performance self-compacting basalt fiber (BF)-reinforced concrete by incorporating waste nanomaterials, namely nano-wheat straw ash (NWSA), nano-sesame stalk ash (NSSA), and nano-cotton stalk ash (NCSA), as partial substitutes for Portland cement. The research evaluates the effects of varying dosages of nanomaterials (ranging from 5 to 15% as cement replacements) in the presence of BFs. Rheological properties were analyzed, including flow diameter, L-box, and V-funnel tests. Additionally, the study investigated compressive, splitting tensile, and flexural strengths, load-displacement behavior, ultrasonic pulse velocity, and durability performance of the ultra-high-performance self-compacting basalt fiber (BF)-reinforced concrete (UHPSCFRC) samples subjected to sulfate attack, freeze-thaw cycles, autogenous shrinkage, and exposure to temperatures of 150, 300, 450, and 600°C. Microstructural characteristics of the mixtures were examined using X-ray diffraction (XRD) analysis. The findings reveal that self-compacting properties can be achieved in the UHPSCFRC by incorporating NWSA, NSSA, and NCSA. The presence of 10% NWSA significantly improved the mechanical properties of the UHPSCFRC, exhibiting more than 27.55% increase in compressive strength, 17.36% increase in splitting tensile strength, and 21.5% increase in flexural strength compared to the control sample. The UHPSCFRC sample with 10% NWSA demonstrated superior performance across all extreme durability tests, surpassing both the control and other modified samples. XRD analysis revealed the development of microcracking at temperatures of 450 and 600°C due to the evaporation of absorbed and capillary water and the decomposition of ettringites.
