Enhancing the flexural performance of ultra-high-performance concrete using long steel fibers

In this study, the flexural performance and fiber distribution characteristics of ultra-high-performance concrete (UHPC) were investigated according to the fiber length. To do this, three different fiber lengths having an identical diameter were used. Enhancements in flexural strength and energy absorption capacity were observed when longer fibers (or higher aspect ratios of fiber) were used, whereas insignificant effect of fiber length on the first cracking properties (i.e., first cracking strength and corresponding deflection) was obtained. Fiber length had a little influence on the degree of fiber dispersion, but a significant influence on the fiber orientation. A higher fiber orientation coefficient along the flow distance was obtained when shorter fibers were used. A finite element analysis incorporating previously suggested material models was performed and verified by comparing the analytical results with the present experimental data.