Determination of linear viscoelastic range for asphalt binders in the dynamic shear rheometer

Abstract Oscillatory amplitude sweeps are essential for determining linear viscoelastic properties of asphalt binders because selection of unsuitable amplitudes can lead to measurement mistakes, material failure and misinterpretation. This study provides extended information and guidelines about the procedure and analysis of amplitude sweeps for asphalt binders. Different rheological parameters to identify the linearity limit are discussed together with recommended shear amplitude values from current international technical Standards. A large set of amplitude sweep tests is performed in the dynamic shear rheometer (DSR) to reveal the effects of test temperature, test frequency, aging state, binder type, test geometry and control mode (shear stress vs. shear strain) on amplitude sweep results and linearity limit. A systematic analysis including considering of the harmonic distortion of the materials sinusoidal response signals allow selection of best suitable shear amplitudes for different test conditions. Test temperature shows the highest influence on the suitable shear amplitudes, with a proposed increase of one decade for a temperature increment of 30 °C. Finally, recommended shear amplitude values were derived and presented in nomograms in function of the temperature for different binder grades in fresh and in RTFOT + PAV-aged states.