Influence of Polymer Type and Dosage on Binder Mix Design Considerations

Abstract

This study investigated the influence of polymer types and dosages on binder mix design
considerations utilising High-Density Polyethylene (HDPE) and Butonal (aqueous SBS polymer)
as modifiers. The initial characterisation of unmodified asphalt binder involved establishing
fundamental properties, namely softening point, penetration index, flash and fire point
temperatures, and specific gravity, which constituted baseline parameters for subsequent analysis.
Subsequently, the asphalt binders were modified through the incorporation of HDPE and Butonal
at concentrations of 2%, 3%, 4%, and 5% by weight. These modified binders were subjected to a
complete evaluation, examining softening point, penetration, and specific gravity to assess
performance variations. Results showed that HDPE modification generally increased binder
stiffness, with higher softening points and lower penetration values, enhancing high-temperature
rutting resistance but risking reduced low-temperature flexibility at excessive dosages. In contrast,
butonal modification resulted in improved elasticity while maintaining penetration values within
moderate ranges, indicating better resistance to thermal cracking. Specific gravity was found to
vary non-linearly with both polymer types and dosages, influencing binder volume and mix
volumetric parameters such as Voids in Mineral Aggregate (VMA) and Voids Filled with Asphalt
(VFA). The findings highlight the need for polymer- and dosage-specific calibration of mix design
to balance stiffness, elasticity, and thermal stability while adjusting binder content to account for
density changes.”