Pavement recycling offers significant economic and environmental benefits through reductions in material and energy consumption cost of construction and user delays. However, there are currently no universally agreed upon rapid process control and product acceptance test methods to ensure that the constructed materials comply with commonly specified parameters and are ready for traffic and surfacing. Asphalt-based recycling agents (foamed asphalt or emulsified asphalt) are used in the following pavement cold recycling processes: cold in-place recycling (CIR), cold central-plant recycling (CCPR), and full-depth reclamation (FDR). Cold recycled materials have traditionally been accepted on the basis of moisture content and compaction in the field and performance tests in the laboratory. These tests do not readily lend themselves to assessing the as-constructed quality and performance of cold recycled materials, nor do they help determine the proper time when traffic and surfacing can be applied without causing damage. Many agencies specify either a maximum moisture content or a mandatory curing period of 2 to 14 days before the recycled layer can accept surfacing. If the actual curing can be measured, significant construction delays may be avoided. Several state DOTs and some local government agencies have developed construction specifications for the various forms of cold recycling, which may vary widely from jurisdiction to jurisdiction. Therefore, a guide specification for process control and product acceptance of cold recycling operations is needed to promote consistency among agencies and allow contractors to more easily operate within multiple jurisdictions. Many existing cold recycling specifications are method-based and generally lack process control and product acceptance tests and criteria. Thus, research is also needed to develop appropriate time-critical tests, generally performed during construction, that allow an agency to quickly determine the quality of the as-constructed cold recycled pavement and evaluate its readiness for traffic and surfacing. The results of this project should lead to the future development of specifications aligned to a quality management approach.
The objectives of this research are to develop (1) time-critical tests for asphalt-treated CIR, FDR, and CCPR materials and (2) a guide specification using these tests for process control and product acceptance that provides the agency with a basis for determining when the pavement can be opened to traffic and surfaced.