ABSTRACT
The paper describes the use of a purpose built hydraulic tension-compression apparatus to investigate the linearity limits and linear viscoelastic (LVE) rheological characteristics of a range of unmodified and modified (polymer and process) asphalt mixtures. The asphalt mixtures consist of dense bitumen macadam (DBM), hot rolled asphalt (HRA) and HRA mortar mixtures with conventional 50 pen bitumen, radial and linear SBS PMBs, EVA PMB and multigrade bitumen. Cylindrical specimens of the mixtures were subjected to sinusoidal loading conditions at temperatures between 10 and 40°C, firstly, under stress sweep conditions and, secondly, under frequency sweep conditions. The results indicate that the linearity limits of behaviour for the asphalt mixtures were strain dependant and found to be between 20 and 100 microstrain for the DBM and HRA mixtures and between 50 and 150 microstrain for the HRA mortars. In general, the LVE rheological characteristics of the asphalt mixtures were similar with differences in complex modulus and phase angle only being found at intermediate temperatures and frequencies and attributed to the unique rheological characteristics of the binders.
