Effect of matrix shrinkage on rate sensitivity of the pullout response of smooth steel fibers in ultra-high-performance concrete

The present study investigates the effects of matrix shrinkage on the rate-sensitive pullout resistance of smooth steel fibers in ultra-high-performance concrete (UHPC) by adding a shrinkage reducing agent (SRA) to the UHPC and varying the fiber inclination angle from 0° to 30°. The pullout resistance is sensitive to the loading rate, and this sensitivity is attributed to both matrix shrinkage and the fiber inclination angle. The addition of the SRA reduces the enhancements in both peak and equivalent bond strengths at higher loading rates. Moreover, the rate sensitivity of the equivalent bond strength increases as the fiber inclination angle increased.