Evaluation of RAP binder mobilisation and blending efficiency in bituminous mixtures: An approach using ATR-FTIR and artificial aggregate

The undetermined extent of reclaimed asphalt pavement (RAP) binder mobilisation is a major apprehension in the design and construction of bituminous mixtures with RAP. This study proposes a new method to quantify the degree of mobilisation of RAP binder and subsequent blending efficiency of RAP mixtures by utilising attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy as an assessment tool. Binders were recovered from laboratory bituminous mixtures with different percentages of RAP prepared under different mixing conditions using glass-based aggregates as tracers. Parameters for assessing the relevant properties were then developed and validated through the means of dynamic shear rheometer (DSR) and gel permeation chromatography (GPC) tests. Lastly, the study was extended to the use of various warm mix additives (WMA) in RAP mixtures. The results indicated that RAP binder mobilisation is highly dependent on temperature and the usage of WMA additives can enhance the mobilisation at lower mixing temperatures. It was also observed that certain chemical additives increased RAP binder mobilisation and blending efficiency to comparable levels of that in hot mix asphalt (HMA) mixtures.