Tensile Fatigue Behavior of Steel Fiber Reinforced Concrete: Correlation Between Fiber Orientation and Mechanical Response

The research presented here analyzes the relation between fiber orientation and fatigue life under tension forces through the combined use of computed tomography (CT), digital image processing (DIP) software and wedge splitting test (WST). To achieve this goal, eight conventional concrete prisms 150 mm × 150 mm × 600 mm were cast and next, sixteen cubes 150 mm edge were extracted, and a groove and notch were carved on different faces in order to force a clearly different fiber orientation with respect to the cracking plane. However, the exact fiber orientations were obtained from a miniprism extracted from the previously mentioned concrete prisms using a CT-scan device and a DIP software. The results show that there is a strong correlation between the crack-sewing fiber orientation on the one hand and fatigue life on the other hand. Cubes with a higher percentage of fibers perpendicular to the crack surface (i.e. with a higher efficiency index) show a longer fatigue life, while cubes with a lower efficiency index show a shorter fatigue life and a higher crack opening rate per cycle.