Evaluating the laboratory long-term ageing behaviour of bio-binders

Bio-binders are considered a promising alternative to petroleum-based bituminous binders. However, due to the wide variety of available biomass sources, fundamental knowledge regarding their chemical and mechanical characterization, as well as their aging behavior in the field, remains uncertain. Thus, the goal of this study is to establish a fundamental framework for the ageing behavior of bio-binders and how they compare to a conventional bituminous binder. Two different bituminous binders and three different bio-binders were subjected to five different laboratory long-term ageing procedures involving exposure to different ageing inducing factors like elevated temperatures in combination with pressure, reactive oxygen species (ROS) and lamps that simulate sunlight. The aged binders were analyzed with Fourier Transform Infrared (FTIR) spectroscopy and Dynamic Shear Rheometer (DSR) and a chemo-mechanical correlation was established for all five binders. Results showed that the complexity of evaluating bio-binders increased significantly compared to unmodified bitumen, as many new bands appeared in the FTIR spectra. One of the three bio-binders, containing vegetable oil, showed a severe ageing susceptibility towards ROS, while the other two bio-binders, containing cashew nut oil or tall oil, as well as the reference binder were more susceptible towards light induced ageing. The study concluded that a universal evaluation via FTIR spectroscopy and DSR, as well as its combination with the chemo-mechanical correlation can provide a good first insight into the materials ageing behavior. However, further detailed studies, involving real-life field ageing trials will be necessary to confirm their ageing behaviors investigated in the laboratory.