AASHTO T 394-21 PDF Download

The AASHTO T 394-21 standard provides a method for determining the fracture energy (Gf) of asphalt mixtures. The test is conducted using the semicircular bend geometry, where a half disc specimen with a notch is used. The length of the notch is expressed in meters, and it makes an angle (a) with the vertical axis of the disc.

The SCB test can be used to determine mode I and mixed mode I and II stress intensity factors. However, this standard specifically addresses mode I fracture toughness, where the angle (a) is equal to zero.

The procedures outlined in this standard aim to evaluate the fracture resistance of asphalt mixtures at low temperatures. The parameters obtained from these procedures, such as fracture toughness (KIC) and stiffness (S), are essential for the new low-temperature module of the Mechanistic Empirical Pavement Design guide.

These procedures apply to test specimens with a maximum aggregate size of 19 mm or less. The specimens should have a diameter of 150 ± 9 mm and a thickness of 24.7 mm ± 2 mm. It is important to note that these procedures are applicable at temperatures below the lower limit of the performance grade (PG) of the asphalt binder used in the mixture, plus 22°C.