Asphalt Modified by Styrene-Butadiene-Styrene Triblock Copolymer: Morphology and Model

Abstract

The styrene-butadiene-styrene ͑SBS͒ triblock copolymer was used to modify the asphalt binder. The morphology and engineering properties of the binders were investigated using transmission electron microscopy ͑TEM͒, rotational viscometer, and dynamic shear rheometer. The morphology of polymer-modified asphalt was described by the SBS concentration and the presence of microstructure of the copolymer. When the SBS concentration increased, the copolymer gradually became the dominant phase, and the transition was followed by a change in engineering properties of SBS-modified asphalt. Results from TEM showed that depending on the asphalt and copolymer source, a variety of morphology can be found. The SBS-modified binders might show a continuous asphalt phase with dispersed SBS particles, a continuous polymer phase with dispersed asphalt globules, or two interlocked continuous phases. The optimum SBS content was determined based on the formation of the critical network between asphalt and polymer. Because of this network formation, the binders showed a large increase in the complex modulus that indicates resistance to rutting. At low SBS concentrations, the Kerner model was found to be appropriate to estimate the rheological properties of SBS-modified asphalt. An adapted Kerner equation was proposed in this study to predict the complex modulus of modified asphalt at high SBS concentrations.

Rheological properties of asphalt/SBS/clay blends

“…At the same time, there is the important and restrictive requirement of the compatibility between the polymer and the asphalt in order to avoid phase separation during storage at high temperatures. Among the recent literature on asphalt modification with block copolymers, the papers by Becker et al [3], Airey [4][5][6], Chen et al [7], Elseifi et al [8], Fawcett and McNelly [9], Wloczysiak et al [10,11], Kumar et al [12], Lu and Redelius [13] should be mentioned.…”

Polymer modification of bitumen: Advances and challenges

“…They believed that PB blocks interact with positively charged groups in bitumen through their π-electrons, whereas PS blocks interact with electron-rich groups in bitumen through their aromatic protons. Mixed with bitumen, PS blocks in SBS copolymers absorb some saturated branches and a few rings in light components of bitumen [115,124], which leads to the swelling of PS blocks and the hardening of bitumen. When the polymer content is low, SBS is dispersed as a discrete phase in the bitumen [115].…”

“…Some popular polymers for bitumen modification are listed in Table 1 with their advantages and disadvantages. Among them, SBS attracted the most attention due to its relatively good dispersibility (or appropriate solubility) in bitumen as well as the relatively excellent properties and acceptable cost of SBS modified bitumen [5,115]. Of course, besides these listed polymers, some others like styrene-butadiene rubber (SBR, random copolymers), styrene-butadiene diblock copolymers (SB) and ethylene-propylene-diene monomer rubber (EPDM) were also popular for bitumen modification [116][117][118].…”

Effect of Superpave Short-Term Aging on Binder and Asphalt Mixture Rheology

“…These networks reinforce the binder, and the interaction between them forms critical networks that cause a sharp increase in the binder complex modulus. The polystyrene end blocks provide the asphalt mix with the strength, while, polybutadiene rubbery matrix blocks provide the mix with needed viscosity (Al-Hadidy and Tan, 2011;Chen et al, 2002). …”