On the impact performance and crack behavior of steel-fiber reinforced concrete beams with SHCC and UHPC strengthening layers

Fiber-reinforced concrete (FRC) is widely used in structures subjected to high strain-rate loadings, such as military facilities, earthquake-resistant buildings, hydroelectric dams, and industrial and highway pavements.Despite significant advances in recent decades, certain structural behaviors remain underexplored, particularly when combining different concretes, such as thin strengthening layers with distinct characteristics, and incorporating different fibers like strain-hardening cementitious composites (SHCC) or even ultra-high-performance concrete (UHPC).Additionally, the application of carbon textiles in these strengthening layers warrants further investigation.This study aims to evaluate the impact resistance of steel fiber reinforced concrete (SFRC) short beams under flexural impact loading, with the addition of SHCC, UHPC, and UHPC layers reinforced with carbon textiles on the tensile face of the beams.The mechanical performance of the composite specimens was assessed through flexural impact tests at varying energy levels.A custom-built drop-weight testing machine, developed at the Structures and Materials Laboratory at PUC-Rio, was used for this purpose.Furthermore, Digital Image Correlation (DIC), in conjunction with high-speed cameras, was employed to measure energy absorption, deformation, and crack propagation in the beams under different configurations and impact energies.The results demonstrated that the SHCC layers significantly improved energy absorption and reduced crack formation.At the same time, the UHPC composites, particularly those reinforced with carbon textiles, exhibited enhanced ductility, energy absorption capacity, and crack control under impact loading.These findings suggest that the improved performance of these composite materials can reduce future repair and reinforcement needs for structures exposed to such demanding conditions.