Correlating the Compositional Changes to the Rheological Properties of Recovered Asphalt Binders from Recycled Asphalt Mixtures: Insights from the Thermogravimetric Measurements

Assessing the binder performance of thermal characterization is critical for quality control. This is pertinent for recovered binders from mixtures, which may not be in adequate quantities to evaluate their performance, particularly in mixtures containing reclaimed asphalt pavement (RAP). The present study deployed a thermogravimetric analyzer to evaluate compositional changes in recovered binders from RAP-containing mixtures, focusing on thermograph and derivative of thermograph (DTG) characteristics and correlating the results to rheological features. Incorporating RAP in mixtures influenced recovered binders’ DTG shapes, reducing low-combusted components (%LCC) and increasing residues (%R). The recovered binder from the zero-RAP-containing mixture showed a 4.36% increase in %LCC and a 1.97% decrease in %R compared to the short-term aged original binder. Binders recovered from RAP-containing mixtures exhibited greater stiffness than the short-term aged original binders. The %LCC dropped from 7.22% to 25.52%, while the %R increased from 20.69% to 33.06%. Uncertainty analyses showed that the DTG area and %R had the least uncertainty and that the %LCC had greater uncertainty. Analysis through regression revealed that DTG area and %R can predict G*/sinδ well, showing a correlation between better thermal stability and binder stiffness. This research puts a number on the correlation between thermal and rheological properties, which helps to improve quality control for binders.