Rheological characterisation of unmodified and modified bitumen in the 90-200°C temperature regime

Developing an understanding of the compaction mechanics during the production process of the bituminous mixture is an essential step in the construction of bituminous pavement. As the binder is mixed with the aggregate particles and subjected to compaction, the binder exhibits interesting transitions from a Newtonian fluid to a non-Newtonian fluid and finally to a viscoelastic fluid. The state-of-art related to determining the mixing and compaction temperature for unmodified and modified binders identify the corresponding viscosities at a specific shear rate, and temperature, however, the complete rheological behaviour of the material during the entire compaction regime is ignored. This investigation tries to address the gap by carrying out the rheological characterisation for one unmodified binder and three modified binders (elastomer, plastomer and crumb rubber) in the temperature regime of 90-200 degrees C. Three protocols were developed for this purpose considering the influence of temperature and shear history. The effect of modification was distinct in the case of elastomer and crumb rubber-modified bitumen, while the rheological response of plastomer-modified bitumen showed a negligible influence of modification. The use of appropriate non-Newtonian models to explain the response of the material for specific cases is demonstrated.