Engineering characteristics of polymer modified asphalt mixtures.

摘要

Asphalt cement is viscoelastic material, which is time and temperature dependent. At high temperatures asphalt cement behaves as a viscous material. At below freezing temperatures it acts as a brittle solid and is more susceptible to temperature cracking. In order to improve both the high and low temperature properties, asphalt binders were modified with various kinds of polymers. In this study, structural and engineering properties of polymer modified asphalt (PMA) mixtures were investigated in lieu of the rheological properties, morphology and adhesive properties of binders.; Experimental program matrices were established for two types of structural tests; indirect tensile strength test and indirect tensile cyclic load test to evaluate the engineering properties of straight and PMA mixtures. The tests were conducted at low (23°F), moderate (77°F) and high temperatures (140°F) for aged and unaged Marshall size samples. Asphalt-polymers mixing procedures were developed based upon the improvement of rheological properties. All asphalt mixtures were designed according to the Michigan Department of Transportation (MDOT) specifications.; The SBS polymer system was selected as a typical polymer to discuss the improvements in the structural and engineering properties due to polymer modification. Comparison of the structural and engineering properties of asphalt mixtures modified with various polymers is presented and discussed. A new fatigue life criterion based on the rate of accumulation of horizontal plastic deformation was developed and compared to the rate of crack growth criteria (based on fracture mechanics). It is shown that the rate of accumulation of horizontal plastic deformation criterion produced consistent and repeatable results for straight and PMA mixtures. Fatigue life and rut depth models were developed based on rheological properties of binders and physical and engineering properties of mixtures.