The objective of the present study was to conduct a comprehensive field experiment for the in situ assessment of in-depth recycled asphalt pavement using foamed asphalt as a stabilization treatment for base works. For this purpose Nondestructive Testing (NDT) data collected using the Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) along a foamed asphalt recycled pavement section was thoroughly analysed. Critical issues including the stabilized material curing and the contribution of the asphalt layers to the structural properties of the in-depth recycled pavement are discussed. In addition, recommendations concerning the improvement of the structural condition of the in-depth recycled pavement are developed based on this practical approach of investigation using NDT. 1. Introduction In-depth recycling is a method implemented worldwide for the rehabilitation of damaged road pavements. One of the major benefits of the method is that the material of a distressed road pavement is simultaneously recycled in-place and mixed with a stabilizing agent, enabling the road pavement to be strengthened without the need to import expensive aggregate. Other benefits include a short construction period, significantly reduced road closures, and improvements relating to safety. These advantages contribute to significantly lower unit costs for road rehabilitation, in comparison with other rehabilitation methods [1]. In addition, environmental issues related to the reuse of road materials increase the advantages of this technology. For the in-depth recycling method, which is often referred to in international literature as cold in-place recycling [2], several types of stabilizers are used for the treatment of the in-place recycled material. The present investigation focuses on the use of foamed asphalt for such stabilization purposes. It is worthwhile to note that this technique has gained popularity in recent years. However, the in-depth asphalt pavement recycling using foamed asphalt as a stabilization treatment for base works requires a certain time period necessary to allow the newly produced foamed asphalt mixture to cure, as is the case for most stabilizing agents, and to build up enough internal cohesion before being covered by a wearing course. Studies have shown that such recycled mixes do not develop their full strength after compaction until a large percentage of the mixing moisture is lost. This process termed “curing” is a process whereby the in-depth recycled and stabilized mix gradually gains strength over time accompanied by a reduction
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