Quantitative evaluation of the restructuring effect of a warm mix additive on bitumen recycling production

Warm mix asphalt (WMA) is a promising technique that allows the production of asphalt at a noticeably lower temperature. One of the methods in use is to add small quantities of specific organic compounds to the asphalt conglomerate. Although it is well established that this procedure leads to an effective reduction of the temperature of asphalt conglomerate production, there is still a lack in the comprehension and description of the real mechanism of the additive action on the colloidal structure. In this work 3D micro-scale atomic force microscopy (AFM) images of fresh, aged and doped bitumen were taken to characterise and study the interaction of a commercial WMA additive with bitumen. We also combined the AFM results with the inverse Laplace transform of the nuclear magnetic resonance relaxation times (T2). Results revealed that the temperature lowering in the WMA recycling procedure is due to the restructuring action of the additive that leads to a re-organisation of the colloidal network of bitumen.