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

TLDR

The study proposes an adapted Kerner equation to predict the complex modulus of SBS‑modified asphalt at high SBS concentrations. The authors modified asphalt with a styrene‑butadiene‑styrene triblock copolymer and characterized its morphology and rheology using TEM, a rotational viscometer, and a dynamic shear rheometer, then developed the adapted Kerner model. They found that increasing SBS concentration shifts the material to a polymer‑dominated phase, forming a critical network that greatly raises the complex modulus and rutting resistance, and that the adapted Kerner equation accurately predicts rheological behavior at high SBS levels.

Abstract

The styrene-butadiene-styrene (SBS) triblock copolymer was used to modify the asphalt binder. The morphology and engineering properties of the binders were investigated using transmission electron microscopy (TEM), 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.