Abstract
The use of reclaimed asphalt pavement (RAP) has been increasing, making better use of resources and reducing the environmental impact of the asphalt industry. Standard asphalt plants have limitations on the RAP content they can accommodate. Additionally, volumetric design methods can limit the content of RAP used to meet specifications. This paper presents a field demonstration of a newly developed asphalt plant using microwave technology. The new design directly heats RAP to warm-mix temperatures, eliminating concerns of degrading materials that arise with high RAP mixtures in a conventional plant. The process reduces plant site emissions while increasing RAP content up to 100%. Balanced mix design was used to select the asphalt binder grade and content, and additives required for a 100% RAP mix design to meet Wisconsin mixture performance requirements. The study demonstrated that the microwave heating process is feasible, and the asphalt mixture meets or exceeds the performance of comparable traditional asphalt mixtures. Results showed that the plant emissions were significantly reduced and below levels permitted in Wisconsin. Also, virgin material inputs were eliminated, except for 0.6% asphalt binder containing additives. Performance testing confirmed that the 100% RAP mixture met specifications for rutting, moisture sensitivity, and cracking resistance. Test sections were surveyed after two years. No visible distress was observed, and field densities were similar for all sections. Recovered binder was subjected to extended aging and was characterized based on performance grade and durability parameters. Results demonstrated that the 100% RAP mixture had equivalent or improved binder aging properties to the control mixtures.
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