Enhancing impact resistance of hybrid ultra-high-performance fiber-reinforced concretes through strategic use of polyamide fibers

This study examines the use of polyamide fibers in improving strain rate sensitivity and impact tensile resistance of hybrid ultra-high-performance fiber-reinforced concrete (hybrid UHPFRC). Two types of long fibers, i.e., smooth steel (S) and polyamide (P), and two types of short fibers, i.e., smooth steel (s) and polyamide (p), were hybridized. The volume content of long fibers was maintained at 1%, whereas that of short fibers varied from 0 to 1%. The blending S and p fibers produced the best performance in term of the ductility and energy absorption capacity of UHPFRC whereas the blending S and s fibers did in term of the ultimate tensile strength. The optimal volume content of short fiber that exhibited improvements in strain rate sensitivity and impact resistance was found to be 0.5%. The p fibers have been successfully used to develop cost-effective hybrid UHPFRC with high impact resistance. (C) 2020 Elsevier Ltd. All rights reserved.