Experimental investigation and identification of single and multiple cracks in synthetic fiber concrete beams

The tensile behavior of fiber-reinforced concrete is recognized as being superior to that of ordinary concrete, and since serviceability is a primary concern in existing design specifications, it is important to evaluate its post-cracking performance. This research experimentally identified and investigated cracks in concrete beams reinforced with synthetic fibers. Concrete beams with and without longitudinal reinforcement were studied in order to assess both single and multiple cracking scenarios. Synthetic fiber volume fractions of 0.5% and 1% were used to prepare the specimens, and the results were compared with those of concrete beams with no synthetic fibers. Six unreinforced beams and six reinforced beams with flexural behavior were tested. The digital image correlation (DIC) method was utilized to record the width, spacing, number, and locations of the cracks for all the specimens during the displacement control-type loading. The results indicated that using 1% synthetic fiber increased the failure load of the reinforced concrete beams and improved the serviceability by reducing the number of cracks and the width of the cracks. When the cracks opened significantly, the beams with 1% fiber dosage were able to carry higher loads due to the bridging action of the fibers at the crack locations.