Quantifying the influence of heating and resting on the bitumen microstructure

Abstract

The investigation of the bitumen microstructure can provide an alternative approach to characterise the material. However, various factors prior to its analysis need to be considered, before being able to come to a meaningful conclusion. This involves the identification of factors like heating time and temperature as well as resting time and how it can affect the resulting microstructure. Furthermore, the need for quantifying the microstructure is sought after. Thus, the goal of this study is to address these parameters and quantify their respective influence via optical inverse dark- and brightfield microscopy, subsequent particle analysis of the darkfield images and partial link to infrared spectroscopy. The results show that optical microscopy in combination with particle analysis from dark field images can be used for quantification of the microstructure and even differentiate binders from different crude oil sources. However, small binder quantities, typically used for microscopy, can oxidize rapidly. Thus, a heating time of 30 – 60 s at a temperature of 150 °C was deemed sufficient for these unmodified binders. In addition to that the microstructure becomes stable after 30 min of resting, making binder characterisation via microscopy much more convenient. For imaging analysis an overall area covered by bee structure enables universal characterisation and comparison, while providing good differentiation between binder A (10%), B (2%) and C (16%). These findings should set the basis for future research, where microscopy can be used to identify and tackle important questions related to changes caused by ageing, modification with polymers, additives, filler or rejuvenators.