Temperature Effects of Linear Amplitude Sweep Testing and Analysis

Fatigue cracking is a critical distress in asphalt pavements. The linear amplitude sweep (LAS) test has recently been proposed for accelerated fatigue characterization of asphalt binders (AASHTO TP 101). The fatigue resistance of asphalt pavements depends on temperature because of the inherent viscoelastic nature of the asphalt binder contained in the pavement. This study sought to develop recommendations for the selection of LAS test temperature based on climatic performance grades (PGs). Developing recommendations for selecting the test temperature involved two components: investigation of climatic data for a wide range of PGs and investigation of the effect of linear viscoelastic dynamic shear modulus on the observed failure mechanism in the LAS test. Results demonstrate that test temperatures should be selected such that linear dynamic shear moduli fall within the range of 12 to 60 MPa to avoid the confounding effects of flow or adhesion loss. On the basis of the aforementioned moduli range-coupled with the analysis of pavement temperature data corresponding to a range of PGs and geographic regions-it is recommended that the LAS test temperature be selected as the average climatic PG minus 4 degrees C. In addition, temperature effects are incorporated into simplified viscoelastic continuum damage modeling of LAS test results to enable the prediction of fatigue performance under any temperature and loading history of interest using LAS test results at a single temperature coupled with linear viscoelastic time-temperature shift factors.