Thermomechanical properties of several polymer modified asphalts: Fid-Bau Portal

Thermomechanical properties of several polymer modified asphalts

Zanzotto, L. / Stastna, J. / Vacin, O.

Costly deterioration of many roads and highways paved with asphalt generates a growing interest in polymer-modified asphalts (PMA). Although asphalt represents only a fraction of asphalt paving mix, it is believed that it has a significant effect on the thermo-mechanical properties of asphalt pavements. Currently there is no consensus on the type of tests and specifications for polymer modified asphalts; however, it is clear that such specifications should be based on rheological testing of these systems. As a viscoelastic material asphalt is usually characterized by its dynamic material functions. An advantage of the use of modified loss tangent function in PMA systems is discussed in this contribution. Three polymer modifiers (SBS, EVA and EGA) commonly used in the asphalt paving industry were blended with base asphalt and various relaxations in the base, and its blends are studied here. The modification of the base asphalt by the studied polymers influences more the high temperature behaviour of blends than the low temperature behaviour. Only for blends of SBS with concentrations of polymer higher than 4 % a shift of the alpha-transition (glass transition) towards the lower temperatures was observed. It seems to be true that the lower concentration of EGA polymer can produce transitions similar to the ones observed in higher concentrations of SBS and EVA, however, only at higher temperatures. The glass temperature transition for 2 % EGA blend is actually higher than the one for the base asphalt i.e. this polymer exhibits slight antiplasticization behaviour. Interestingly enough, the higher concentration SBSr blend behaves as plasticizer (Tg is shifted to lower temperatures); however, various high temperature mechanical transitions (observed on the graph of the modified loss tangent) decrease in intensity with increasing polymer content (this being a characteristic of antiplasticizers). Generally by adding a polymer to the base asphalt the main transition (observed as the maximum of the modified loss tangent and lying between the alpha and alpha' transitions) will split at least into two with increasing separation of these maxima and decreasing intensity, when the concentration of the polymer is increased.