THE STRUCTURE OF POLYMER MODIFIED BINDERS AND CORRESPONDING ASPHALT
MIXTURES
Wegan, V;Brule, B
Abstract
As a part of the Strategic Highway Research Program (SHRP), the Danish Road Institute has developed an
optical method for evaluation of asphalt mixtures by microscopy of thin and plane sections. The method is
based on the technique used to examine and characterize the microstructure of Portland Cement Concrete.
In this study, the preparation technique has been modified , making it possible to examine the structure of
the polymer modified binder directly in the asphalt mixture. The structure is observed under a microscope
with UV-light by illuminating the surface of a cut and sections. The polymers used were SBS and EVA
type polymers. It is important to be able to examine the structure of the polymer modified binder in the
asphalt mixture since the chemical interaction and structural build-up of the polymer phase is influenced by
several factors. It is well known that mechanical treatment and mixing temperature affect the quality of the
polymer modified binder. In addition, the cooling rate influences how the polymer structurizes in the binder
during placement and compaction of the final asphalt pavement. The study has shown that an interaction
exists between the polymer phase and the aggregates in the asphalt mixture, indicating that it is very
difficult to establish performance based specifications for polymer modified binders. Hence it would be
most sensible to evaluate the performance of the polymer modified asphalt mixture from tests on the actual
asphalt mixture.