Post-fire residual mechanical properties of concrete made with molybdenum tailings as substitute fine aggregates

Rising demand for natural sand in construction harms ecosystems, prompting interest in alternatives like mining tails. This study explored using molybdenum tailings (MoTs) as partial replacements for fine aggregates in concrete. Specimens were prepared with various MoT ratios to evaluate their post-fire mechanical properties at temperatures of 200℃, 400℃, 600℃, and 800℃. MoT concretes (MoTCs) displayed failure modes similar to ordinary concrete, with higher temperatures leading to more severe failures, greater weight loss, and diminished residual mechanical properties. Notably, higher MoT content significantly improved post-fire performance. In specific, specimens with 25 % MoT showed a 7.90 % increase in Poisson's ratio and a 16.03 % improvement in splitting tensile strength after 3 hours at 600℃. At 800℃, the peak stress and elastic modulus of specimens with 75 % MoT rose by 51.66 % and 53.85 %, respectively. Further, predictive models for post-fire performances were proposed, offering a practical approach to incorporating MoT aggregates in concrete structures.