Evaluation of Resistance to Rutting and Moisture Susceptibility on High RAP content Asphalt Concretes using Hamburg Wheel Tracking Device

Reclaimed or recycled asphalt pavement (RAP) stands for materials that are removed and reprocessed asphalt pavement materials. It is usually from asphalt road maintenance and reconstruction. Past research has proved that the use of RAP will save natural resources by incorporating the old asphalt and aggregates into the new asphalt paving material production. This practice results in cost reduction in roadway construction and maintenance, and thus benefits both the agencies and the public. However, there is a concern over the strength and durability of the pavements containing high RAP content because the old asphalt binder and aggregates aged by traffic and climate over time have low adhesion between asphalt binder and aggregates and this characteristic may cause stripping and cracking in asphalt pavements. The objective of this study was to evaluate the durability of high RAP asphalt paving materials through a laboratory test using Hamburg Wheel Tracking Machine (HWTM) at high temperature (50, 64C). HWTM has the ability to measure the resistance of asphalt materials to rutting and moisture damage. The experiment employed asphalt materials commonly used in the state of Georgia, including two asphalt binder types (PG 64-22 and PG 76-22 w/ modification), multiple aggregate sources, and RAP sources. Up to 30% of the RAP by the total mix weight was used. The experiment matrix resulted in nine difference mixes including 80 test specimens. The specimen production and the test were in compliance with the American Association of State Highway and Transportation Officials standards (AASHTO T 324). Based on the partial test results, the following findings were observed. 1) Most of the RAP mixes with PG 76-22 show very high durability to rutting in both test temperatures, 2) The RAP mixes with PG 64-22 show relatively lower durability to rutting in both test temperatures as compared to the PG 76-22 mixes, 3) Control mixes without RAP show low durability to rutting in both test temperatures, and 4) Even though there is little rut depth in the RAP mixes, stripping distress was observed to some degree. This project is sponsored by Georgia Department of Transportation and the test program and data analysis are currently on going. This abstract contains only part of the research results