Early-Age Autogenous Shrinkage and Cracking Risk of 5D Hooked-End Steel Fiber–Reinforced High-Strength Concrete under Uniaxial Restrained Condition

Abstract

The incorporation of steel fiber exhibits great benefits to reduce cracking risk and autogenous shrinkage (AS) of high-strength concrete (HSC). 5D hooked-end steel fiber (5DSF) is a kind of novel hooked-end steel fiber. Previous investigations mainly focused on the mechanical properties and shrinkage deformation of 5DSF reinforced HSC (5DSFRC). However, the early-age cracking risk of 5DSFRC under uniaxial restrained conditions considering temperature evolution, AS, and restrained stress simultaneously has not been thoroughly investigated. A temperature stress test machine, which is capable of measuring these factors simultaneously, was used to investigate the effect of 5DSF volume fraction (0%, 0.12%, 0.24%, and 0.36%) on the early-age cracking risk of HSC in the present study. Experimental results and analysis showed that the cracking age, cracking stress, ratio of cracking stress to axial tensile strength, and reserve strength of HSC increased with an increase in 5DSF volume fraction. The AS of HSC decreased with an increase in 5DSF volume fraction, and an AS formula was proposed to calculate the early-age AS of HSC reinforced with steel fiber considering the effect of the volume fraction and shape of the fiber. The cracking risk of HSC decreased with an increase in 5DSF volume fraction. The early-age cracking risk and AS of HSC reinforced with 5DSF were lower than that of HSC reinforced with 3D hooked-end steel fiber with a similar steel fiber volume fraction.