SBS Modified Bitumens: Does Their Morphology and Storage Stability Influence Asphalt Mix Performance?

This paper studies the influence of morphology and storage stability of polymer modified binders on the mechanical performance of asphalt mixes, in particular permanent deformation and fatigue characteristics. Four 70/100 pen bitumens of different crude origins and a linear SBS were selected to prepare polymer modified binders (PmBs). The binders showed differences in morphology, storage stability and in phase separation diagram; their rheological properties were found to be strongly morphology-related.

This paper studies the influence of morphology and storage stability of polymer modified binders on the mechanical performance of asphalt mixes, in particular permanent deformation and fatigue characteristics. Four 70/100 pen bitumens of different crude origins and a linear SBS were selected to prepare polymer modified binders (PmBs). The binders showed differences in morphology, storage stability and in phase separation diagram; their rheological properties were found to be strongly morphology-related. 

To study the asphalt mix, a dense graded asphalt was selected. Mixing was conducted at 180°C, and asphalt specimens were prepared at the same temperature using a gyratory compactor. Permanent deformation and fatigue were characterised by triaxial test at 50°C and indirect tensile test at 10°C, respectively. It was shown in loose mixes and in compacted specimens that all PmBs displayed a similar morphology and that the polymer was seen as a discontinuous phase. In the triaxial test, little differences were found in final accumulated strains between the different mixes. The mixes also behaved similarly with respect to the amount of recoverable strain. However, the mixes differed largely in the fatigue performance. The fatigue and permanent deformation of the mixes had no relation to the differences in the storage stability and morphology of the modified binders. The present study also suggests that mix performance will not be properly predicted by testing PmBs if the morphology in the binder deviates from that in the mix.

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Authors

X. Lu, H. Soenen, P. Redelius