Observation of bitumen microstructure oxidation and blending with ESEM

There have been a several studies observing bitumen microstructure using the environmental scanning electron microscope (ESEM); however, these have been few and far between. Nevertheless, there have been findings that show microstructure under ESEM clearly evolving with bitumen ageing. The objective of this paper is to focus on sample conditioning, oxidation and blending. A conditioning procedure was produced and the effect of freezing (−18°C) on the bitumen microstructure for 19 h was examined. A straight-run PG 58-28 bitumen was sampled, with the same bitumen being oxidised using hot air. Additionally, these two bitumens were mixed at ratios of 25/75, 50/50 and 75/25. The microstructures were compared with ESEM observation for their relative density, organisation and fibril size, clearly showing an evolution in the microstructure with oxidation and with different blending ratios.