Prediction of Low-Temperature Cracking Using Superpave Binder Specifications: Fid-Bau Portal

Prediction of Low-Temperature Cracking Using Superpave Binder Specifications

Kandhal P. S. / Dongre R. / Malone M. S.

Six different AC-20 asphalt cements were used in a Pennsylvania project in September 1976. Two of the six test pavements developed low-temperature cracking in January 1977. The remaining four test pavements started to develop cracks to different degrees after three years. This project has been well documented in the literature during its 7 years service life. Data such as rheological properties of original and aged asphalt cements, hourly air and pavement temperature, and yearly crack surveys, have been reported. The samples of these six asphalt cements which were saved from 1976 to 1995 (19 years) have now been tested using Superpave binder test procedures such as bending beam rheometer (BBR). This research project was undertaken to verify whether these Superpave test procedures and specifications could have predicted the low-temperature cracking of the six AC-20 asphalt cements in the Pennsylvania project. The maximum stiffness criteria of 300 MPa and the minimum m-value criteria of 0.30 recommended in Superpave binder specifications generally appear to be reasonable in mitigating low-temperature cracking. However, the behavior of one asphalt cement (T-3) could not be explained by these criteria. Although Asphalt T-3 had stiffness exceeding 300 MPa at the minimum design temperature it did not crack at all during its 7 years service life. There are some indications from ductility data that Asphalt T-3 may have a high failure strain. However, this needs to be confirmed by direct measurements at low pavement temperatures using the Superpave direct tension tester (DTT).