Effect of long-term aging on fracture properties of virgin and recycled asphalt concrete

Oxidative aging stiffens asphalt in the pavement, raising brittleness, cracking potential, and deterioration of pavement serviceability. Mechanical testing of long-term aged asphalt concrete in the laboratory has shown elevated stiffness, higher failure load (peak load), and reduced fatigue cracking resistance. Among the laboratory mechanical tests used to evaluate mix fatigue resistance and flexibility is the semicircular bend (SCB) test. This study was conducted to determine how the properties of the long-term aged asphalt mixes compare with those fromshortterm aged asphalt mixes tested under SCB test. Such comparison is important as a decision needs to bemade bymix designers as to what aging level to apply when testing asphalt concrete to evaluate fatigue resistance. The mix variables included air void, binder content, and binder stiffness. The properties that were measured, i.e., the response parameters, included fracture energy, load at failure (peak load), mix stiffness, and flexibility index. A large number of mixes including various aggregates, gradations, and binder contentswere included in the study. Results showed that long-term oven aging significantly changed flexibility index, peak load, and stiffness of tested specimens. Sensitivity of the parameters to aging was also evaluated in the context of an aging index and defined as the ratio of the measured property after long-term aging to that after short-term aging. In this respect, the aging index did not change as the binder content changed. However, the aging index was sensitive to variations in air void and binder stiffness.