Experimental investigation of the homogeneity of the blended binder of a high rate recycled asphalt

Nowadays, with the increasing material costs and the environmental needs to reduce energy consumption and greenhouse gases emission, the technique of asphalt recycling becomes more and more used in the road industry. To ensure the performance of recycled asphalt, a quality control of the bituminous mixture is required. In this context, this work was carried out within the framework of a partnership between the IRC/ESTP and the company Eurovia. In this paper, we present an experimental approach to characterise the level of blending of the binder from reclaimed asphalt pavement (RAP) in hot recycled bituminous mixture. First, a series of laboratory tests are performed on asphaltic concrete including 70% of RAP to extract the bituminous binder mixture using an appropriate solvent. This leads to define an appropriate progressive extraction procedure that allows a regularly stripping of the recycled concrete (three solutions containing about 30% of the bituminous binder). Then, both conventional tests and infrared spectroscopy analysis are performed in order to quantify the evolution of the RAP and virgin binders mass proportions during the stripping process. The experimental results show a “bad” remobilisation of the virgin bitumen in the blended binder of the hot recycled bituminous mixture. This finding correlates with the hypothesis of the “heterogeneous asphalt” considered during the manufacture process.