The rehabilitation of failed flexible (asphalt) pavements is often an expensive process, especially if the pavement has base or subgrade problems and a simple overlay will not result in a long-term solution. This is the case with many low-volume roads, where minimum pavement structures are required to carry heavy traffic, leading to pavement deterioration. A procedure is available, called full-depth reclamation with portland cement (FDR-PC), which allows these failed asphalt pavements to be recycled and stabilized, creating a new base that will provide an excellent foundation for long-term pavement performance. After a roadway has been selected as a candidate for FDR-PC, a field evaluation should be performed to determine what materials make up the current pavement structure and what lead to the pavement failure. The principal reason for the field evaluation (core samples or test holes) is to determine the thickness of the in-place pavement layers, and to obtain samples of the materials in each layer that will be blended for the reclaimed base. Material sampling can typically include the asphalt surface, base course aggregate, and subgrade soil. Material samples from the site should be pulverized in the laboratory to create a soil/aggregate mix that will be similar to that expected from the reclamation process. A standard soil-cement mix design procedure is followed to determine what the proper amount of cement should be for the reclaimed base material, as well as the determination of maximum dry density and optimum moisture content. If unconfined compressive strength is used to determine cement content, typical seven-day strengths between 2.1 and 2.8 MPa (300 and 400 psi) are recommended. This paper will discuss the sampling and testing of in-place roadway materials and how they should be evaluated in the laboratory to ensure they meet the requirements for a FDR-PC pavement.
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