Evaluation of Cold In-Place and Cold Central-Plant Recycling Methods Using Laboratory Testing of Field-Cored Specimens

摘要

During the 2011 construction season, the Virginia Department of Transportation (VDOT) completed a major pavement recycling project that marked the first time full-depth reclamation (FDR), cold in-place recycling (CIR), and cold central-plant recycling (CCPR) were used together on a single project on the US interstate system. The CIR and CCPR mixtures were produced by using foamed asphalt and hydraulic cement as the stabilizing agents. After completing the pavement rehabilitation project, engineering properties of the CIR and CCPR mixtures were determined in the laboratory from field-cored specimens. VDOT conducted this study because the agency was considering using a single set of construction specifications for both CIR and CCPR materials if the engineering properties of the two processes were found to be similar. This project offered a unique opportunity to evaluate the two recycling methods by using materials from the same location. Laboratory tests included gradation, binder content, density measurements, indirect tensile strength (ITS) measurements, and resilient modulus (M_R) testing. ITS and M_R were selected because ITS has traditionally been used for the design and acceptance of recycled mixtures, whereas M_R testing offers a step toward mechanistic pavement design in its use in Mechanistic Empirical Pavement Design Guide/ DARWin-ME software. The results demonstrated that differences in the engineering properties of the recycled materials, as produced by CIR and CCPR, are not statistically significant. Previously, information was limited in the literature to support designs using pavement recycling, or using CCPR in particular, as another option for highway agencies seeking to use a more environmentally friendly option to rehabilitate pavements. The results presented in this study will also help pavement engineers to better recognize the range of material properties possible with recycled mixtures.