# Dynamic Constitutive Model of Basalt Fiber Concrete After High Temperature Based on Fractional Calculus

## TL;DR

This paper develops a new model to predict how basalt fiber concrete behaves under high temperatures and impact, using fractional calculus.

## Contribution

A novel dynamic constitutive model for basalt fiber concrete is proposed using fractional calculus to capture thermal and mechanical behavior.

## Key findings

- BFRC's dynamic compressive strength decreases with higher temperatures but increases with higher impact rates.
- The model accurately captures BFRC's mechanical behavior across elastic, viscoelastic, and viscous states after high-temperature exposure.
- Basalt fibers improve stress transfer, while high temperatures increase viscous behavior due to microstructural damage.

## Abstract

Concrete materials undergo a series of physical and chemical changes under high temperature, leading to the degradation of mechanical properties. This study investigates basalt fiber-reinforced concrete (BFRC) through high-temperature testing using the split Hopkinson pressure bar (SHPB) apparatus. Impact compression tests were conducted on specimens after exposure to elevated temperatures to analyze the effects of varying fiber content, temperature levels, and impact rates on the mechanical behaviors of BFRC. Based on fractional calculus theory, a dynamic constitutive equation was established to characterize the viscoelastic properties and high-temperature damage of BFRC. The results indicate that the dynamic compressive strength of BFRC decreases significantly with increasing temperature but increases gradually with higher impact rates, demonstrating fiber-toughening effects, thermal degradation effects, and strain rate strengthening effects. The proposed constitutive model aligns well with the experimental data, effectively capturing the dynamic mechanical behaviors of BFRC after high-temperature exposure, including its transitional mechanical characteristics across elastic, viscoelastic, and viscous states. The viscoelastic behaviors of BFRC are fundamentally attributed to the synergistic response of its multi-phase composite system across different scales. Basalt fibers enhance the material’s elastic properties by improving the stress transfer mechanism, while high-temperature exposure amplifies its viscous characteristics through microstructural deterioration, chemical transformations, and associated thermal damage.