Experimental Investigation into the Multiscale Performance of Asphalt Mixtures with High Contents of Reclaimed Asphalt Pavement

Hot-mix asphalt (HMA) mixtures with high content of reclaimed asphalt pavement (RAP) have been investigated and applied in the laboratory and in plants. An asphalt mixture can be considered as a four-scale assemblage of components with different characteristic length scale, binder, mastic, mortar, and finally mixture. This paper investigates the mechanical properties of HMA mixtures with high RAP contents through the multiscale of binder, mortar, and mixture, and analyzes the property correlations between them. RAP contents of 30, 50, and 85% were adopted for tests; meanwhile fresh asphalt (0%RAP) and 100%RAP were also prepared for comprehensive comparison. Frequency sweep test, repeated creep test, and bending beam test were used to measure the properties of mortars, meanwhile, dynamic modulus test, flow number test, and semicircular bending (SCB) test were used to measure the properties of mixtures. It is found that with the increase of the RAP content, binder, mortar, and mixture show similar changes of mechanical properties, behaving as complex modulus increases with viscoelasticity reduce, and rutting resistance improves, whereas thermal cracking resistance declines. The mechanical properties of binder, mortar, and mixture at high and low temperature are well related. Fine aggregates have significant influence on the high-temperature properties of mortars, and the mixture modulus is highly affected by coarse aggregates.