Mechanical behavior and fiber reinforcing mechanism of high-toughness recycled aggregate concrete under high strain-rate impact loads

Fiber-reinforced recycled aggregate concrete (FRRAC) is renowned for its excellent mechanical properties and environmental benefits, making it a popular choice in construction engineering. However, the impact damage mechanisms of FRRAC remain unclear. This study leverages advanced in-situ 4D CT technology to investigate the fiber-reinforcing mechanisms of High-Toughness Recycled Aggregate Concrete (HTRAC) using construction waste as a sustainable building material. Under high strain-rate conditions, the dynamic mechanical behaviors of both plain recycled aggregate concrete (PRAC) and HTRAC were examined using the Split Hopkinson Pressure Bar (SHPB) method. The experiments revealed significant strain rate sensitivities in both materials, with HTRAC showing superior fiber reinforcement that markedly enhances its toughness. Quantitative models for dynamic increasing factors of key mechanical parameters, including peak stress, peak strain, initial elastic modulus, ultimate strain, and toughness index, were developed. These findings offer critical design insights for using HTRAC in impact load conditions and other extreme environments, promoting its wider adoption in the construction industry.