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The structure of polymer modified binders and corresponding asphalt mixtures Wegan, Vibeke ; Brule, Bernard ; Lefebvre, Jean

By: Contributor(s): Series: Rapport ; 92Publication details: Roskilde Vejdirektoratet. Vejteknisk institut, 1999Description: 28 sISBN:
  • 8790145569
Subject(s): Bibl.nr: VTI P0031:92Location: Abstract: The Danish Road Institute has developed an optical method for evaluation of asphalt mixtures, making it possible to examine the structure of the polymer modified binder directly in the asphalt mixture. The structure is observed under a microscope with UV-light by illuminating the surface of cut and polished specimens of the asphalt mixture prepared as thin or plane sections. It is important to be able to examine the structure of the polymer modified binder in the asphalt mixture since it is influenced by several factors. The polymer modified binder will be subjected to oxidation and degradation during mixing, storage and transportation of the hot mix asphalt. The cooling rate influences how the polymer structurizes in the binder during placement and compaction of the asphalt pavement. This, together with a possible physico-chemical interactions of the polymer phase and the surface of the mineral aggregates, are all factors which greatly affect the structure of the polymer modified binder and finally the performance of the asphalt mixture. The main conclusion from the microscope investigations of 25 laboratory produced asphalt mixtures is that the structure of the pure polymer modified binder in most cases is not the same as the structure of the polymer modified binder in the asphalt mixture. In the asphalt mixtures, the polymer phase is observed as small spots or as smaller or larger irregular globules in a continuous asphalt phase. For EVA modified asphalt mixtures, the EVA phase can in addition be observed as a film around the surface of the mineral aggregates. The EVA phase obviously has an affinity to the coarse aggregate, which seems to be influenced by the amount of mineral filler. For SBS modified binders this affinity to the mineral aggregates has not been observed. The study has shown that an interaction exists between the polymer phase and the aggregates in the asphalt mixture, indicating that it is very difficult to establish performance based specifications for polymer modified binders. Hence, it would be most sensible to evaluate the performance of the polymer modified asphalt mixture from tests on the actual asphalt mixture.
Item type: Reports, conferences, monographs
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The Danish Road Institute has developed an optical method for evaluation of asphalt mixtures, making it possible to examine the structure of the polymer modified binder directly in the asphalt mixture. The structure is observed under a microscope with UV-light by illuminating the surface of cut and polished specimens of the asphalt mixture prepared as thin or plane sections. It is important to be able to examine the structure of the polymer modified binder in the asphalt mixture since it is influenced by several factors. The polymer modified binder will be subjected to oxidation and degradation during mixing, storage and transportation of the hot mix asphalt. The cooling rate influences how the polymer structurizes in the binder during placement and compaction of the asphalt pavement. This, together with a possible physico-chemical interactions of the polymer phase and the surface of the mineral aggregates, are all factors which greatly affect the structure of the polymer modified binder and finally the performance of the asphalt mixture. The main conclusion from the microscope investigations of 25 laboratory produced asphalt mixtures is that the structure of the pure polymer modified binder in most cases is not the same as the structure of the polymer modified binder in the asphalt mixture. In the asphalt mixtures, the polymer phase is observed as small spots or as smaller or larger irregular globules in a continuous asphalt phase. For EVA modified asphalt mixtures, the EVA phase can in addition be observed as a film around the surface of the mineral aggregates. The EVA phase obviously has an affinity to the coarse aggregate, which seems to be influenced by the amount of mineral filler. For SBS modified binders this affinity to the mineral aggregates has not been observed. The study has shown that an interaction exists between the polymer phase and the aggregates in the asphalt mixture, indicating that it is very difficult to establish performance based specifications for polymer modified binders. Hence, it would be most sensible to evaluate the performance of the polymer modified asphalt mixture from tests on the actual asphalt mixture.