Automated Non-contact Resonance Excitation Method for Low Temperature Behavior of Asphalt Concrete

This paper studies the applicability of an automated non-destructivetesting method to monitor the stiffness of asphalt concrete at lowtemperatures. A loudspeaker is used as a source of non-contact excitation ofthe axially symmetric fundamental resonance frequencies of a disc-shapedasphalt concrete specimen positioned inside an environmental chamber. Measuredresonance frequencies are used to calculate the dynamic moduli of the specimenat different temperatures. The repeatability of the method as well as theeffect of loudspeaker height above the sample are studied. Results show thatthe main advantage of the non-contact excitation method, compared to manuallyapplied impact hammer excitation, is that repeatable automated measurements canbe performed while the specimen is placed inside an environmental temperaturechamber. This methodology enables to study the effect of only low temperatureconditioning on the dynamic modulus of asphalt concrete without interferencefrom mechanical loading.QC 20181210