AASHTO TP 124-16

This test method covers the determination of the fracture energy (Gf) of asphalt mixtures using the semicircular bend (SCB) geometry at an intermediate test temperature. The method also includes procedures for calculating other relevant parameters derived from the load-displacement curve. These parameters, in conjunction with field performance, can be used to develop a Flexibility Index (FI) to predict an asphalt mixtures’ damage resistance. The index can be used as part of the asphalt mixture approval process.

These procedures apply to test specimens having a nominal maximum aggregate size (NMAS) of 19 mm or less. Lab compacted and field core specimens can be used. Lab compacted specimens shall be 150 ± 1 mm in diameter and 50 ± 1 mm thick. When field cores are used, specimens shall be 150 ± 8 mm in diameter and 25 to 50 mm thick. A thickness correction factor may be applied for field cores tested at thickness less than 45 mm.

A vertical notch parallel to the loading axis shall be cut on the SCB specimen. The SCB specimen is a half disc with a notch parallel to the loading and the vertical axis of the semicircular disc.