Nonrecovered compliance from dynamic oscillatory testvis-à-visnonrecovered compliance from multiple stress creep recovery test in the dynamic shear rheometer†The opinions, findings and conclusions expressed in this document are those of the author and not necessarily of the Federal Highway Administration or other researchers at the Turner-Fairbank Highway Research Center.

Nonrecovered compliance is presently being viewed as the most appropriate rheological parameter for evaluating the propensity of an asphalt binder to resist permanent deformation or rutting in the pavement wheel paths. The nonrecovered compliance can be obtained in two ways using two different types of tests in the dynamic shear rheometer. One is through the dynamic oscillatory test using a frequency, time, strain or stress sweep, wherein the data generated is in terms of the complex modulus and phase angle that can be used in a proper mathematical form to obtain the nonrecovered compliance. The other is through the multiple stress creep and recovery test wherein the nonrecovered strain at each stress level after 10 cycles of creep and recovery is divided by the stress value to obtain the nonrecovered compliance. The two methods are very different in the way data gets generated and handled and, also, in the level of ease or difficulty in data generation. With two methods competing to come up with the same outcome, it is important to see a comparison of the merits and demerits of each of the methods in order to ascertain which of the two is more reliable, more fundamental, easier to use and better to implement. The purpose of this paper is to provide a one-on-one comparison between the two methods using the same set of binders and also to look at the possible benefits of one over the other.