Influence of the Instrumental Inertia Effect on the Asphalt Binder Oscillation Measurement

Inertia effect is an artifact commonly seen in the oscillation test for soft materials. It is due to the misattribute of the instrument's elastic component to the sample's properties, which will lead to overestimated storage modulus (G ') and underestimated phase angle (d). Inertia effect is widely recognized for bio materials; however, it has not been fully understood for asphalt binder. This article aims to investigate the instrumental inertia effect in the asphalt binder oscillation test. In this study, one plain asphalt, eight elastomeric modified asphalts (EMAs), and six non-elastomeric modified asphalts (non-EMAs) are examined using the oscillation test for a wide temperature range (40 degrees C-140 degrees C). The inertia effects that occurred during the testing are characterized and discussed. It is found that inertia effects also happen to asphalt binders, especially for non-EMA. The existence of inertia effect can be identified by the raw phase parameter being greater than 90 degrees. Increasing the strain amplitude of the oscillation test may alleviate the inertia effect. This might be due to the improved signal/noise ratio of the data. To eliminate the inertia effect artifact during the asphalt binder oscillation measurement, this study recommends a stress-control oscillation test (50 Pa), combined with a lower strain limit of 1% and an upper strain limit of 100%. The results suggest that by using the stress-control approach, the inertia effect can be eliminated and accurate measurements for G ' and phase angle can be obtained.