Reclaimed Asphalt Pavement Detection and Quantity Determination

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures provides the means to recycle the existing roadway and use that material, in a limited amount, in the construction of new pavements. This is an environmentally friendly method to recycle the existing pavement and provide a new pavement surface. While this is a most economical means of pavement rehabilitation, the life of the overlay is generally 10 to 20 years before rehabilitation is pursued. As a new overlay is placed, the previous overlay is milled, creating RAP. The amount of available RAP material in the U.S. is considerable and continually increasing, and the use of RAP as a component in new mixes is strongly supported by the asphalt industry. However, currently, there seems to be no method to control the quantity of RAP in an asphalt mix. This is due to the differences in plant readout units that vary based on plant types and contractor practices. As part of a larger research project to devise a test that can identify the presence and quantity of RAP in hot-mix asphalt pavements, this paper presents the state of the art research conducted on RAP and RAP detection. The paper also presents the results of a survey conducted to investigate the availability of a RAP detection and quantity determination method used by the various states. It was concluded that at the current time, there is no specific test available that would accurately determine the presence and quantity of RAP in hot-mix asphalt.