Laboratory Investigation of Effect of Reclaimed Asphalt Pavement (RAP) on Bitumen and Hot Mix Asphalt

Resources, rocky materials and bitumen, environmental problems due to the production of reclaimed asphalt pavement (RAP), and economical benefits have caused the exploitation of existing materials to become one of the most important deterioration objects in road and pavement industry. Asphalt concrete mixture hot recycling is one of the appropriate methods of patching, improvement and reconstruction of asphalt mixtures. In this method, the destroyed and deteriorated asphalt layer is chipped and will be reused in new asphalt concrete composition. There for it is necessary to have more researches about the appropriate performance of reclaimed asphalt pavements. Because bituminous in RAP, during performance and service life because of reaction with air get stiff and old, evaluation of combined bituminous (RAP bituminous and fresh bitumen) is very important. In this research, characteristics of HMA bitumen consisting different percentages of RAP (0, 25, 50, 75, 100) after recovery such as penetration grade, softening point, ductility property and viscosity are evaluated. Also some other tests such as marshal and indirect tensile test are done.Results show that the RAP bituminous is much stiffer comparing with fresh bituminous. Also the bituminous in mixtures without RAP during construction was stiffer than the initial used bituminous. According to the results it was found that adding RAP to the Asphalt mixtures leads to increasing in stiffness of new bitomious which is used in mixture construction and in mixtures with higher amount of RAP, combined bitominous characteristics (Bitominou of RAP and new bitominous) are similar to charach tristics of RAP bitominous.