An experimental study on the effects of steel fiber type and content on the tensile properties of ultra-high-performance concrete

Abstract

Ultra-high-performance concrete (UHPC) is a construction material characterized by exceptional mechanical properties, particularly high compressive strength and long-term durability. However, its crack resistance beyond the elastic limit remains limited. The incorporation of steel fibers has emerged as an effective approach to enhance the tensile performance and post-cracking ductility of UHPC. This study investigates the influence of fiber types and volume contents on the tensile behaviors of UHPC through experiments using three types of steel fibers (smooth, twisted, and hooked fibers) at volume fractions of 0.5%, 1.0%, and 1.5%. Results indicate that the initial tensile strength at first cracking is not significantly affected by fiber type or content. However, as the fiber content increases, there is a significant enhancement in post-cracking strength, tensile strain capacity, and energy absorption. Notably, twisted and hooked-end fibers outperform smooth fibers due to their superior mechanical interlocking with the cementitious matrix. These findings highlight the critical role of fiber geometry and dosage in optimizing the tensile performance and overall mechanical behavior of UHPC under tensile loading.