Thermal and Mechanical Performance of Ultra-high-performance Basalt Fiber Concrete Incorporating Nano Agricultural Waste Additives at Ambient and Elevated Temperatures

This study explored the development of sustainable ultra-high-performance basalt fiber high-strength concrete (UHPBF-HSC) using agricultural waste materials. Nano-sugarcane bagasse ash (NSCBA), nano cotton straw ash (NCSA), and nano rice straw ash (NRSA) were incorporated as partial cement replacements. Additionally, basalt fiber (1.5%), silica fume (10%), and superplasticizer (0.5%) were consistently included in all mixes. The nanoparticles were produced through mechanical processing and heat treatment. Four dosage levels (5-20% by weight of cement replacement) were tested in combination with basalt fibers. The study evaluated the effects of elevated temperatures (300℃ and 600℃) on UHPBF-HSC, focusing on compressive strength (CS), strength degradation, mass loss, ultrasonic pulse velocity, splitting tensile strength (STS), flexural strength (FS), and water absorption. Results indicated that increasing nanoparticle dosage generally enhanced mechanical properties. Among all mixes, the NSCBA4 (M4) mix exhibited superior performance, achieving approximately 9.7% and 23.0% higher CS than the corresponding NCSA4 and NRSA4 mixes, respectively, at identical replacement levels, in addition to outperforming conventional concrete. The mixes NCSA and NRSA showed similar performance but were less effective than NSCBA. Scanning electronic microscopic analysis revealed well-bonded matrices and compacted sections under normal conditions. However, elevated temperatures led to microcrack formation due to ettringite decomposition and water evaporation. A comparative analysis and prediction of STS and FS were conducted using various codes and literature sources.