Effect of Carbon Fibers on Fracture Toughness of Asphalt Mixtures Using Linear Elastic Fracture Mechanics

There are several methods to investigate the behavior of hot mix asphalt (HMA) at low temperatures. One of these methods is the use of principles of linear elastic fracture mechanics (LEFM). In this paper, the LEFM principles is used to investigate the effects of different loading modes and temperatures on the fracture resistance of HMA incorporating carbon fibers at subzero temperatures. Three-point fracture tests were successfully performed on the semi-circular bend (SCB) specimen containing an asymmetric vertical edge crack under different modes of loading including pure mode I (pure tensile), pure mode II (pure shear) and mixed-mode I/II (tensile-shear). Critical stress intensity factors were then computed using the critical load obtained from the fracture experiments and the geometry factors were determined from the finite element analyses. Results revealed that at all loading modes, modified HMA has higher resistance against crack growth than the unmodified HMA, particularly at low temperatures. Also, fracture resistance of tested HMA was improved by 30-43 percent in the pure tensile mode, 13.2-41 percent in the mixed mode (Me=0.5), 10.5-40 percent in the mixed mode (Me=0.2) and 2-12.5 percent in the pure shear mode.