On the microstructure of bituminous binders

The objective of this work is to study the common features and the evolution of microstructures of bituminous binders regardless of their grade (PEN 10/20 to 160/220) and source/origin using the atomic force microscope operated in phase contrast mode. All bituminous binders show the same microstructural features, consisting of three distinct phases, the perpetua-, peri- and catana-phase. The perpetua-phase is soft and viscoelastic in nature, the peri-phase is relatively stiff and solid in nature and the catana-phase is alternatingly hard and soft in nature and is always found in the middle of the peri-phase. Experiments at different temperatures result in a quantitative picture of the changes/transitions between the different microphases upon heating. Phase formation is reversible with respect to temperature, upon heating homogenisation occurs and upon cooling re-formation of the phases can be observed.