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The laboratory performance and modification mechanism of asphalt modified with Sasobit and Polyphosphoric acid (PPA) were studied through a comprehensive laboratory program. The base asphalt was mixed with 3% Sasobit to produce Warm Mix Asphalt (WMA) and then modified with four different percentages of PPA (0.5%, 1.0%, 1.5% and 2.0%) by mass of base asphalt, respectively. The rolling thin film oven (RTFO) and the pressure aging vessel (PAV) procedures were conducted to simulate the aging of asphalt. Experiments were conducted for asphalts under different aging conditions. The rheological property of asphalt was measured by conventional tests, the Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR). The morphological characteristic of asphalt was evaluated by Fourier Transform Infrared Spectroscopy (FT-IR), Fluorescence microscopy, Thermogravimetric (TG) and Differential Scanning Calorimetry (DSC). It is concluded that the rheological properties of asphalts were enhanced after Sasobit and PPA were added. The penetration of asphalts decreased and softening point increased, proving that deformation resistance was enhanced and high-temperature stability improved. The ductility decreased to an acceptable level when the PPA content was less than 1.0%. High-temperature deformation resistance and aging resistance were enhanced for asphalts under different aging conditions. In order to guarantee the low-temperature property of asphalt, PPA content in WMA should be no more than 1.5%. The modification effect of Sasobit and PPA on asphalt included chemical and physical processes. The compatibility between PPA, Sasobit and base asphalt is good and the microstructure of the modified asphalt is beneficial in improving the performance of asphalt. The addition of Sasobit restricted the decomposition process of the asphalt component, and the addition of PPA further alleviated the decomposition process and enhanced the stability of asphalt. [ABSTRACT FROM AUTHOR]

In this study, the objective was to conduct a laboratory investigation of rheological and morphological properties of warm mix asphalt containing polyphosphoric acid (WMA-PPA). The Superpave binder tests (i.e., rotational viscosity test, dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test) as well as microscopic tests (i.e., Fluorescence microscopy, Fourier transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimetry and Thermogravimetry (DSC/TG) test) were performed to determine the influences of polyphosphoric acid (PPA) on warm mix asphalt binders. The experimental design included six binders and four different polyphosphoric acid dosages (by weigh of neat asphalt). The test results indicated that, the addition of PPA into warm mix asphalt binders exhibited an increase in the viscosity at different test temperatures, giving clear indication of the modification effects of PPA on the warm mix asphalt binders’ high-temperature performances. Temperature and frequency sweep tests show that the WMA-PPA binders demonstrate lower value of phase angle and higher value of complex modulus compared with the WMA binder regardless of aging state, the WMA-PPA asphalt containing more PPA has higher values of complex modulus (lower values of phase angle) than the WMA-PPA asphalt with less PPA in original state and after RTFO aging state. Bending beam rheometer (BBR) test illustrates that the addition of PPA making the low temperature rheological properties of the WMA binder worse. Furthermore, the amount of PPA has a great effect on the microstructures and hot storage stability of WMA-PPA asphalts, and the modification effect of PPA on WMA asphalt is a chemistry process. The 1.5% of PPA was found to be the optimum content between the studied percentages due to the warm mix asphalt binder containing 1.5% PPA achieved comparative good intermediate and high temperature rheological properties and at the same time is considered economical. [ABSTRACT FROM AUTHOR]