Investigation of Mechanical Behavior and Fracture Energy of Fiber-Reinforced Concrete Beams and Panels

This study quantifies the role of carbon fibers as micro-reinforcement in round panels to prevent and slow the formation of cracks. While carbon fiber-reinforced concrete (CFRC) has drawn considerable attention for use in pavements, the majority of CFRC performance assessment is limited to laboratory-scale samples which do not conform to the predominant failure mechanism, yield-line theory, for concrete pavements. In this study, the effects of carbon fiber content and length on flowability, fiber-matrix bond, and mechanical properties were studied and compared to polypropylene fiber. Analysis of the quadratic polynomial fitted surface plot helped to find the most effective fiber content and length. Composite theory was used to predict the flexural strength, and the result were compared to that of experimental results. The last phase consisted of concrete round panels tested under center-point bending in which the failure mechanism under yield line theory was analyzed. Analysis of Variance (ANOVA) model was finally adopted to compare the calculated modulus of rupture in beams and panels. The results showed beneficial effect of CFRC on pre-crack energy absorption, and their role as crack retarders was justified when the absorbed energy was compared to non-fibrous mixes. The residual flexural strength was also improved in beams and round panels reinforced with carbon fibers. Using the composite theory, the experimental-to-predicted flexural strength ratios in PAN-based carbon fibers were in the range of 1.11–1.34. However, the predicted strengths of mixtures with polypropylene and pitch-based carbon fibers were significantly higher than the experimental values.