AASHTO TP 124-20 PDF Download

AASHTO TP 124-20 is a provisional standard method of testing that is used to determine the fracture potential of asphalt mixtures at intermediate temperatures. The method involves using a semicircular bend (SCB) geometry and measuring the fracture energy (Gf) of the asphalt mixture. This test method allows for the calculation of other relevant parameters from the load-displacement curve. These parameters, along with field performance data, can be used to develop a Flexibility Index (FI) that predicts the damage resistance of the asphalt mixture.

This standard applies to asphalt mixtures with a nominal maximum aggregate size (NMAS) of 19 mm or less. The test can be performed on both lab-compacted specimens and field cores. Lab-compacted specimens should have a diameter of 150 ± 1 mm and a thickness of 50 ± 1 mm. Field cores should have a diameter of 150 ± 8 mm and a thickness of 25 to 50 mm. A thickness correction factor may be applied for field cores tested at a thickness less than 45 mm.

To conduct the test, a vertical notch parallel to the loading axis is cut on the SCB specimen. The specimen itself is a half-disc shape with the notch parallel to both the loading axis and the vertical axis of the semicircular disc. This test method provides a standardized approach for assessing the fracture potential of asphalt mixtures at intermediate temperatures.