Research Note: Field Investigation of Pavement Rehabilitation Utilizing Cold in-place Recycling with Bitumen Emulsion (Initial study, Operation and Performance Process)h

While cold asphalt pavement recycling technologies are well established, there is still a need for additional performance information. Project selection is among the most important factors in assuring the success of a cold in-place recycling project. In this research after investigating the rehabilitation process of Semnan- Damghan highway as a case study, some practical recommendations have been presented which could assist to select a proper project for rehabilitating with recycling technique. In the first stage of field study in addition to the field surveying of pavement condition, both destructive and nondestructive tests have been carried out and the rehabilitation design has been performed with indirect and direct design methods. Based on obtained results Semnan-Damghan highway was divided in to several sections and rehabilitated with conventional and cold recycling rehabilitation techniques. The total length of rehabilitated areas was equal to 165 km which 104 km of them were rehabilitated with recycling technique.After that the pavement performance was monitored during 5 years. Selected techniques were satisfactorily performed in about 154 km of rehabilitated areas. In about 11 km of recycled areas some structural failures were detected after only 6 months from project accomplishment. Precise field surveys revealed that the low compaction and load carrying capacity of subgrade materials and lack of proper base or subbase layers were some reasons of project failure in these areas. Furthermore, there were some shortcomings in the recycled layer specifications which resulted in adverse results. Finally some quantitative criteria were proposed which could be used as practical guidelines in decision of selecting a project to be rehabilitated with cold recycling.