New regulations on bitumen fumes and aerosols, along with increasing traffic and climatic loads on highways, demand innovative construction materials. In this investigation, a novel isocyanate-based bitumen additive was used to pave 0.5 km of an asphalt binder layer with 50% reclaimed asphalt at 20-30°C below hot mix asphalt (HMA) temperatures, in Germany. During construction, bitumen fumes and aerosols were measured for both reference and modified asphalt mixtures. The reference mixture was paved using a similar mixture but with standard polymer modified bitumen, at standard HMA temperatures. For the investigation, a bitumen 70/100 was modified with 2.0% by wt with this novel isocyanate-based additive in an in-line procedure directly at an asphalt mixing plant without affecting production times. Bitumen and asphalt tests were conducted in the laboratory, on asphalt gathered from the construction site. Due to the temperature reduction, the emissions could be considerably reduced, while maintaining comparable asphalt performance..
With the rapid growth of traffic demands, using liquid chemical material instead of traditional modifier to prepare high-performance modified asphalt demonstrates dual values in environmental protection and performance improvement of pavement. The objective of this study is to assess the efficiency and reveal the modification mechanism of using a developed polyurethane-precursor based reactive modifier (PRM) in the preparation of polyurethane-precursor modified asphalt (PMA). The selected petroleum asphalts (60/80 pen grade) were modified at 1.5%, 2.5% and 4% by weight. Samples of the base asphalt and PMA binders were characterized by Dynamic Shear Rheometer (DSR), Time Sweep (TS) fatigue test and Single Edge Notched Beam (SENB) tests.The modification mechanism was finally demonstrated by the fraction analysis, Fourier-transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeter (DSC), Atomic Force Microscopy (AFM), Fluorescence Microscope (FM). Due to the presence of polar groups in neat asphalt, the usage of PRM can be treated as a chemical method for the modification and it shows good compatibility with neat asphalt. The incorporation of PRM to the asphalt matrix can remarkably improve the hightemperature performance and fatigue resistance of asphalt. Besides, the PMA presents desirable low-temperature crack resistance and aging resistance. Considering the relatively low level of preparation temperature (145°C) and the huge improvement in high-temperature performance, the modification using PRM can be regarded as an environmentally friendly alternative for the production of polymer modified asphalt, especially at high-temperature regions.
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