Laboratory Validation of Viscoelastic Interconversion for Hot Mix Asphalt

Various research efforts have proven that it is possible to interconvert the various linear viscoelastic material properties (i.e., the creep compliance, relaxation modulus, complex compliance, and dynamic modulus) of asphalt concrete materials. The interconversion makes it possible to predict one viscoelastic property from another and therefore eliminates the need to do more than one test to calculate all needed viscoelastic properties. This paper presents a laboratory validation of the interconversion between dynamic moduli and creep compliances obtained from two typical mixes used in the Commonwealth of Virginia. The measured dynamic modulus was successfully converted into creep compliance, and the measured creep compliance was successfully converted into dynamic modulus. Both converted properties were compared to the actual measured data. It was found that in most cases the converted properties were similar to the measured properties. However, the dynamic modulus predicted smaller creep compliance than was measured while the creep compliance predicted smaller dynamic modulus than was measured. This is attributed to the fact that the creep tests were performed at high, constant stress without confinement, which might have brought the material outside its linear viscoelastic range. More testing is therefore needed to confirm the promising results obtained with the existing conversion methods.