The flexural behavioral properties of ultra high performance concrete (UHPC) low-profile T-beams reinforced with a combination of steel fibers and steel reinforcing bars were investigated in this paper. Five large scale T-beams were tested and analyzed regarding their deflection, ductility, strain, curvature, load capacity and crack development. The experimental variables include the reinforcement ratio, the slenderness (length to diameter ratio) of the fiber reinforcements, and the fiber type. The experiments showed that all specimens exhibit flexural failure with the yielding of steel bars and excessive expansion of flexural crack, and the compression zone in the reinforced UHPC low-profile T-beam is not crushed because of the ultra high compressive strength and area of UHPC. In addition, it was concluded that using hooked-end fibers can effectively increase the specimen’s durability-based cracking load in comparison to straight fibers of same slenderness, whereas the reinforcement ratio and the slenderness of the fibers have little influence on this. Increasing the reinforcement ratio and using hooked-end instead of straight fibers increase the load capacity and bending stiffness of the specimen, as well as reduces the crack width at comparable applied load. A model was established to compute the ultimate capacity of UHPC low-profile T-beams and the prediction agrees well with the experimental results in the present and published investigations.

Ultra-high-performance fiber reinforced concrete (UHPFRC) exhibits strain hardening and multiple cracking behaviors when subjected to tension load. There are limited studies on the effect of steel fiber aspect ratios on the tensile performance of UHPFRC. Also, tensile testing of cementitious materials and composites is challenging due to the lack of a standardized direct tensile testing method with wide variation. This study experimentally investigated the effect of hooked end and straight steel fiber aspect ratios on the tensile behavior of UHPFRC with a 2% fiber volume fraction. A direct tensile test setup was first developed to obtain good alignment and desirable experimental data in an attempt to overcome some of the difficulties with other tensile tests. UHPFRC failure modes, stress-strain relationships, initial cracking strength, and peak strength, as well as stress–crack width relationships, were characterized and analyzed. The developed tensile test results showed that, as the aspect ratio of the hooked end fiber increased, the ductility ratio and the characteristic stress increased. However, the effect of the straight fiber aspect ratio on tensile behavior was not more significant than that of the hooked end fiber aspect ratio. Over-large straight fiber aspect ratios led to a reduction in characteristic stress and ductility ratio and an acceleration of crack propagation in the early softening phase. In comparisons of the developed direct tensile test and other test methods in terms of peak strength, the small-scale briquette tensile test showed the potential to become an alternative to conservatively evaluate UHPFRC composition strength of.