Rheological characterization of bituminous binder to predict pavement rutting

Abstract

The original Superpave bituminous binder specification to warrant against rutting was based on G*/sin theta as measured in the dynamic shear rheometer (DSR) at the upper pavement temperature. Recent research has suggested a repeated creep test conducted in rotational shear with the DSR as a more appropriate specification test for grading PG binders at the upper grading temperature. On the other hand, zero shear viscosity (ZSV) has been proposed as a potential specification criterion in Europe. Data obtained from the static creep and recovery test or from a DSR frequency sweep can be used to estimate ZSV. Different binders consisting of common base bitumens and different modifiers with varying levels of modification were tested using repeated shear, static creep and recovery, and DSR frequency sweeps over a range of test temperatures and stress levels. Different materials exhibited different responses in repeated shear and these responses are discussed with respect to the amount and type of modifier. Different types of structuring appear to occur in the binders and this structuring, which is different for plastomers and elastomers, can affect the response of the binder to repeated shear. The nature of the recovery is evaluated with respect to modifier type and dosage level. Finally, the utility and accuracy of ZSV as determined from dynamic and static creep testing is discussed. Comparisons between the different parameters are evaluated and their relevancy as specification parameters is discussed. For the covering abstract see ITRD E117423.