Paper Number
GS28 

Session
Gels and Self-Assembled Systems

Title
Viscoelastic behavior of asphalt-polyolefin physical gels

Presentation Date and Time
October 12, 2017 (Thursday) 9:05

Track / Room
Track 4 / Crestone A

Authors (Click on name to view author profile)

1. Zhao, Xiaofei (Texas Tech University, Chemical Engineering)
2. Dissanayaka, Tharanga (Texas Tech University, Civil, Environmental, and Construction Engineering)
3. Rahman, Minhazur (Texas Tech, Mechanical Engineering)
4. Christopher, Gordon F. (Texas Tech, Mechanical Engineering)
5. Senadheera, Sanjaya (Texas Tech University, Civil, Environmental, and Construction Engineering)
6. Hedden, Ronald (Texas Tech University, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Xiaofei Zhao¹, Tharanga Dissanayaka², Minhazur Rahman³, Gordon F. Christopher³, Sanjaya Senadheera², and Ronald Hedden^1
1Chemical Engineering, Texas Tech University, Lubbock, TX 79409; ²Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409; ³Mechanical Engineering, Texas Tech, Lubbock, TX 79409

Speaker / Presenter 
Hedden, Ronald

Text of Abstract
Asphalts are complex mixtures of hydrocarbons and heteroaromatics that are widely employed as binder materials in flexible pavements. In order to extend pavement lifetime, the binder material must provide resistance to both rutting (in warm weather) and cracking (in cold weather). Polymeric materials have widely been employed as modifiers, especially copolymers of styrene and butadiene. However, relatively little work has examined crystallizable polymers as modifiers for asphalts. Our recent work has revealed that a slightly crystallizable copolymer of propylene (PP) and ethylene (PE) can enhance the rheological characteristics (viscosity, stiffness, elasticity) of asphalt binders in the rutting temperature range of 50 to 70 °C without requiring major modifications to pavement mix design or processing conditions. The PP/PE copolymer is miscible with the asphalt at a concentration of 5 % by weight at the "hot mix" temperature of 163 °C, producing only a modest increase in steady shear viscosity. However, as the polymer/asphalt solution cools, a robust physical gel forms, dramatically altering rheological behavior at lower temperatures. The polymer also induces phase separation into asphaltene-rich and maltene-rich phases during cooling, while formation of semicrystalline polymer fibrils stabilizes the morphology. These materials exhibit rubber-like elastic recovery near room temperature, leading to performance enhancements in both freshly prepared and aged asphalt concretes. The rheological behavior of the polyolefin-modified asphalt binders has been characterized in steady and dynamic shear, while stiffness and creep were evaluated by bending beam rheometry at temperatures < 0 °C. Optical and fluorescence microscopy have been applied to characterize the morphological features of the gels, which govern the observed rheological phenomena.