Investigation on Compaction Warm Mix Effect of Plant Hot Recycled Asphalt Mixture

The compaction of plant hot recycled asphalt mixture (PHRAM) is the key to ensuring road performance. In this paper, sixteen groups of PHRAM and eight groups of warm mix asphalt mixture are chosen to investigate whether PHRAM possesses warm mix properties and to confirm the compaction mechanism. The Marshall and Gyratory Testing Machine (GTM) compaction methods are used to compare and analyze the compaction behavior of PHRAM with different mixture compositions. Then, the warm mix mechanism of PHRAM is studied using a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS). The results indicate that PHRAM is more easily compacted than the new asphalt mixture through the GTM method, which is more pronounced given the reclaimed asphalt pavement (RAP) content. In addition, the degree of compaction at the equilibrium state is 0.8%–2.8% higher than that of the new asphalt mixture, and the temperature can be reduced by 20°C–30°C. The compaction law of PHRAM is consistent with that of the new asphalt mixture given the surface-active warm mix agent. Through microscopic analysis, the microstructures of porous characteristics and small particles that adhered to the surface of RAP particles contributed to the good compactability of PHARM. In addition, the miscibility inhomogeneity between the aged and new asphalt is distributed in a three-dimensional space, which has an interface sliding effect and promotes the warm mix effect of PHARM. This paper can provide insights into the compaction characteristic of PHARM, offering guidance for optimization of and adjustment to the compaction temperature.