No abstract

No abstract

Oxidative age hardening of bitumen results in increasing fatigue susceptibility of bituminous mixtures, thus reducing the service life of asphalt pavements. Polymer additives to bitumen have been shown to improve its viscoelastic properties and, in some cases, reduce the level of bitumen hardening. Fourier transform infrared (FT-IR) spectroscopy enables evaluation of oxidation levels in bitumen by measuring the concentration of oxygen-containing chemical functionalities. This paper summarizes the results of the investigation of oxidative age hardening of polymer-modified bitumens (PMB) caused by accelerated aging in laboratory conditions. The PMB samples are prepared with different concentrations of styrene-butadiene-based co-polymers. Next, the PMB samples are aged using standard procedures that employ air blowing at 163 °C for 85 min followed by conditioning the samples at 100 °C and 2.1 MPa pressure for 20 to 48 hours. The resultant changes in their chemical composition are evaluated by portable attenuated total reflection (ATR) spectrometer. Measurements of ketone, sulfoxide, and hydroxyl content in PMB samples indicated similar oxidation pathways to those of non-modified bitumens. In addition, no evidence of polymer degradation due to accelerated aging of PMB was found in this study.

No abstract

This paper is based on the experimental results from the New England Transportation Consortium project titled "Establishing Default Dynamic Modulus Values for New England". The dynamic modulus (|E * |) test results for 20 different dense-graded hot mix asphalt mixtures from five states in the Northeast US Region were compared with predicted |E * | values from Andrei-Witczak and Hirsch models as well as ENTPE transformation. The factors influencing measured |E * | values and prediction errors were also evaluated. The results showed that binder grade, air voids, and presence of reclaimed asphalt pavements (RAP) significantly affect |E * | values of asphalt mixtures. Statistical analysis of |E * | predictions revealed a similar level of underestimation produced by the three models over the high temperatures) >40 • C). However, at medium and low temperatures (<25 • C) the ENTPE transformation clearly outperforms two other models by yielding on average very small errors.