Quantifying the impacts of biochar on asphalt mastics

Abstract: One of the critical issues currently faced by the asphalt industry is incorporating new materials which provide an advantage in terms of performance and environmental impacts, of which bioproducts can serve as one option. Biochars derived from mass pyrolysis of organic waste are a good candidate given the amounts of these wastes which are available and chemical compositions which are generally compatible with asphalt materials. To assess the impacts of biochars, we developed and conducted a mastic testing suite which includes the recently validated mastic poker chip test, frequency sweep testing using the dynamic shear rheometer (DSR), and thermal stability/microscopic testing. We also conducted gas chromatography/mass spectroscopy (GC-mS) testing to determine the impact in terms of reduction of volatile emissions at higher temperatures from the binders. Initial results indicate that biochar has capabilities to improve the stability of asphalt mastics and provide good mechanical performance, as long as it is dosed appropriately. Furthermore, advanced characterization using microscopic techniques helps uncover the mechanisms by which different biochars affect asphalt performance. Overall, the results of this study show the potential for different biochars from a range of organic sources to partially replace fillers and fine aggregates in asphalt mixes. The difference and importance of pyrolysis process used is also shown.