Application of the Maximum Undamaged Defect Size (dmax) Concept in Fiber-Reinforced Concrete Pavements

Many fiber types are used in fiber-reinforced concrete (FRC) pavements. The maximum undamaged defect size (dmax) concept has been applied to predict notch-based fracture in different types of concrete. The present paper applies this concept to different types of FRC pavement, namely, glass fiber-reinforced concrete pavement and steel fiber-reinforced concrete pavement. Due to the quasi-brittle manner of concrete, various fracture models have been developed to study the crack propagation in the pavement structures. The fracture energy was determined based on the recommendation of the RILEM Committee 50-FMC. An experimental study was carried out to investigate the effect of adding short fiber, steel or glass, in controlling the fracture energy of concrete. The analysis was invoked for constant fiber length of 25mm. The flexure test of single-edge notched and unnotched specimens was performed using three-point bending configuration. Four different values of crack-depth ratios were considered, mainly, 0.00, 0.10, 0.25, and 0.40. Experimental results showed that the calculated dmax based on RILEM Committee 50-FMC is greater than the maximum aggregate size (MAZ). This means that there is no compatibility between the flexural strength of FRC and its fracture energy calculated based on RILEM Committee 50-FMC. Therefore, a modified calculation of the area of load-deflection curve was suggested to improve the reliability of fracture energy measured based on RILEM Committee 50-FMC. It is found based on this modification that dmax is less than 0.7 MAZ.