Low-Temperature Thermal Cracking of Asphalt Binder by Asphalt Binder Cracking Device

Abstract

An asphalt binder cracking device (ABCD) is proposed to determine the low-temperature cracking potential of an asphalt binder. ABCD is a simple test method; the operating principle is based on the differential thermal contraction between the metal ABCD ring and an asphalt binder placed outside the ring. As the temperature is lowered, the test binder shrinks more rapidly than the ABCD ring placed inside; this results in the development of thermal stresses. When the developed thermal stress exceeds the strength of the binder, the binder specimen cracks. Strain gauges installed inside the ABCD ring detect the fracture, and the temperature is recorded as the ABCD cracking temperature. With a number of modified and unmodified binders, ABCD repeatability was studied. On the basis of this study, the ABCD and its test procedures were modified to produce repeatable results. In laboratory tests of unmodified and polymer-modified asphalts, ABCD showed a strong correlation with thermal stress restrained specimen test results. Also, ABCD cracking temperatures of the binders used in the well-known Elk County, Pennsylvania, test road correlates well with the cracking index of the test pavements.