Long-term effects of RAP on the mechanical properties of cold recycled mixtures

Abstract

ABSTRACT This paper investigates the long-term influence of aged asphalt in reclaimed asphalt pavement (RAP) on the mechanical properties of the cold recycled mixture (CRM) with emulsified asphalt. Firstly, RAP was simulated by the long-term aging method. On this basis, indirect tensile strength tests were conducted to discern the long-term strength with different aged asphalt dosages (0%, 2%, and 4%) and aging degrees (0, 4, 8, and 15 h) of RAP. After accelerated curing, the indirect tensile strength (ITS) and fracture energy () were measured and the area ratio of uncoated aggregates of the fractured surface (Ra ) was established by image processing to reflect the long-term growth mechanism of strength. Considering the unfavourable states, interfacial drawing and shear tests were executed with different aging degree, load, interfacial contact and thickness of aged asphalt films. Results indicated that the strength increased with aged asphalt dosages of RAP, whereas aging degree had the opposite effect. Moreover, aging degrees, clean surface and external load are all salutary to the long-term adhesion of CRM, obviously. Therefore, it is proved that RAP makes contributions to the long-term growth in mechanical properties of CRM, which is also significant to sustainable asphalt pavement maintenance.