Full-depth recycling (FDR) with foamed bitumen is increasingly being used worldwide for the rehabilitation of highway pavements. Numerous research projects have been undertaken and guideline documents written to help practitioners with implementing the technology. However, much of this work is focused on pavements with thin surfacings overlying relatively thick granular or lightly cemented bases. In California, most roads where FDR is being considered consist of multiple asphalt concrete overlays, constructed either directly on the subgrade, or on thin layers of imported material. Therefore, the recycled material consists primarily of cracked asphalt pavement. Initial research by the University of California Pavement Research Center, in partnership with the California Department of Transportation and the South African Council for Scientific and Industrial Research began in 2001 to investigate FDR on thick, cracked asphalt pavements to support development of more cost-efficient and sustainable pavement rehabilitation strategies. Although the study is not complete, early findings have confirmed that international practice based on thin surfacings/thicker aggregate bases is not always relevant to recycling of thicker asphalt pavements. In this paper, an overview of the California research is described, early findings from pilot projects and laboratory investigations are summarized, and recommendations towards improved practice are discussed. (a)
Samenvatting