Low-Temperature Rheology of Asphalt Cements—Rheological Background

This paper, which is the first of a proposed series, reviews selected published information on the low-temperature flow properties of asphalt cements obtained by creep procedures and dynamic techniques over temperatures below 25°C (77°F) and down to −20°C (−4°F) and lower. A comprehensive summary is given with comments on the magnitudes of the reported viscoelastic parameters (elastic, stiffness, and viscosity) and relevance of the results to other test properties. It is suggested that simplifying approximations in available apparatus may be equally useful for evaluating the rheological creep behavior as obtained in constant stress test modes. These suggestions are implemented by experimental creep measurements on two paving and two roofing asphalts over temperature ranges from 150 down to −5°C (302 to 23°F). It is demonstrated that a reasonably correct fit of the data results for a Maxwell-Kelvin modified five-parameter model. It is recommended that the use of stiffness values as a function of time together with a power law relation for viscosity is a realistic approach for evaluating low-temperature properties of asphalt cements.