Evaluation Methodology Of Temperature Susceptibility For Paving Asphalt

The temperature susceptibility of asphalt binder, which is a key index for asphalt, has close relationship with the paving and service performance of asphalt pavement. Hence, it is very important to evaluate the temperature susceptibility of asphalt binder. There are a couple of evaluation indexes for the temperature susceptibility of asphalt binder, and the empirical indexes are the dominant part. However, there is no index reflecting the true mechanical properties of asphalt binder. In this study, 6 regular asphalts and 6 lab modified asphalts were chosen as the objects. The penetration index (PI) as the evaluation method was investigated firstly. Then, the penetration-viscosity model was discussed. Rheological indexes were established with dynamic shear rheometer (DSR), bending beam rheometer (BBR), and rotational viscosity rheometer (RV) to evaluate the temperature susceptibility of asphalt binders at different temperature zones. Grey entropy method, stepwise regression, as well as neural network were applied to correlate the regular indexes of asphalt with its rheological indexes. The following conclusions can be drawn on the basis of the aforementioned study.Penetration indexes of 12 asphalt binders were determined through different temperature combinations. The results indicated that the PI value has high sensibility and poor stability. PI values, which were obtained via different penetration values at different temperatures and different temperature variation, have great difference. Meanwhile, PI value is the variation of asphalt viscosity within a very narrow temperature scope, which will cause deviations when extrapolated to higher or lower temperature zones.Saal-Koens/Carré-Laurent model and Robert model were applied to transfer the penetration value as the condition viscosity of the asphalt binder at the same temperature. Then, the viscosity-temperature relation can be used to characterize the temperature susceptibility of asphalt, which expands the temperature zone.Temperature susceptibility of asphalt binder can be characterized at different temperature zone with different indexes. The change rate of creep stiffness with temperature (SAS) is proposed to evaluate the temperature susceptibility of asphalt binder at low temperature zone. The change rate of elastic modulus with temperature (GAG') is proposed to characterize the temperature susceptibility of asphalt binder at medium-high temperature zone. Slope (n) of viscosity-temperature curve is employed to describe the temperature susceptibility of asphalt binder at high temperature zone.The results of the grey entropy analysis indicate that softening point and penetration values at 5℃and 10℃have large effect on n. Penetration value at 35℃, softening point and penetration value at 25℃influence GAG' dominantly. While Penetration value at 5℃and 10℃, and breaking point have main effect on SAS.Four empirical correlations were obtained between regular indexes and rheological temperature susceptibility indexes through stepwise regression analysis, in which the mean absolute error ranges from 2.10×10^-2 to 4.19×10^-4 and the mean relative error varies from 0.50% to 0.87%. This indicates the above four correlations have good accuracy. Meanwhile, a neural network was established between the two types of indexes and the good predicated results were obtained.