How Temperature and Loading Rate Affect the Yield Behavior in Polymer-modified Asphalt Systems

Abstract

This paper reports on how temperature and loading rate affect the low-temperature yield properties of two asphalts (California Valley and Bow River sources), straight and modified with 5% by weight of four commonly used commercial polymers (styrene–butadiene diblock, triblock and radial and ethylene–vinyl acetate copolymers). The Bow River asphalt was also tested with the addition of mineral filler. Both the source of the bitumen as well as the nature of the additive and the presence of filler were found to have a significant influence on how the yield stress changes with temperature and loading time. Only one homogeneous, California Valley binder modified with SBS triblock copolymer, provided a typical Eyring plot with a constant activation energy of 42 kJ/mol and activation volume of 3.7 nm³. Other systems showed atypical behavior in that the activation parameters changed rapidly with both temperature and rate of loading.

Keywords:

• Asphalt
• Polymer modifier
• Thermal stress cracking
• Yield stress and Fracture toughness

Acknowledgements

Special thanks goes out to the various chemical companies for kindly supplying the polymer samples. The MRL established under the Strategic Highway Research Program in Reno, Nevada, and Golden Bear Oils of Oildale, California, are thanked for providing the asphalt binder samples. Financial support from the National Cooperative Highway Research Program (NCHRP-IDEA Contract No. 84), the Charitable Foundation of Imperial Oil of Canada, the Ontario Ministry of Transportation and the Natural Sciences and Engineering Research Council of Canada is also gratefully acknowledged.