Linear Viscoelastic Performance of Asphaltic Materials

ABSTRACT This paper describes the linearity limits of various unmodified and modified bituminous binders as well as asphalt mixtures incorporating these binders. The linearity limits of the binders and mixtures have been determined using a dynamic shear rheometer (DSR) and a purpose-built dynamic, uniaxial tension-compression, servo-hydraulic testing apparatus respectively. Both continuously graded as well as gap-graded asphalt mixtures have been tested together with a fines/filler mortar (mastic). The results show that there are strain dependent linearity criteria for both binders and asphalt mixtures at high binder stiffness values as well as a high temperature strain dependent linearity criterion for elastomeric modified binders at temperatures greater than 60°C. The linearity strain criterion for the asphalt mixtures was found to be in the order of 100 microstrain with the criterion for the binders being at least 100 times greater at just over 10,000 microstrain (1% strain) and the elastomeric polymer network strain criterion at 1,000,000 microstrain (100% strain). In addition, the conventional, process modified and plastomeric polymer modified binders displayed a stress dependent linearity criterion of approximately 5kPa at low binder stiffness values.