ABSTRACT
When a rod is performing torsional vibrations at one of its resonance frequencies, any interaction with a viscoelastic medium will change both its resonance frequency and it’s damping characteristics. By measuring this change, one can obtain the viscoelastic material properties of the medium. The new high frequency torsional dynamic resonance rheometer presented below is based on this principle. The device is very robust in environments involving spurious low frequencies, which makes it ideal for in situ measurements. In the present case, a polymer modified asphaltic plug joint of a Swiss highway was monitored continuously from August 1998 until December 2000. The data on resonance frequencies and damping have been interpreted by means of a mechanical model involving both the vibrating sensor and the portion of the bituminous binder participating in the vibrations. The values for damping and elastic constant of the bituminous binder have been recovered from this model. These values give clear indications on the long-term influence of climate and ageing on the material.
The experimental field results obtained over a time span of several years show that the data from the high frequency rheometer lead to valuable information for material optimisation and improved performance behaviour of asphaltic plug joints.
