On the microstructure of bituminous binders

Abstract

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.