Full-Depth Recycling Study: Test Track Construction and First Level Analysis of Phase 1 HVS and Laboratory Testing

This first-level report describes the first phase of a study comparing the performance of four different full-depth pavement reclamation strategies, namely pulverization with no stabilization (FDR-NS), stabilization with foamed asphalt and portland cement (FDR-FA), stabilization with portland cement only (FDR-PC), and stabilization with engineered asphalt emulsion (FDR-EE). A literature review, the test track layout and design, stabilization and asphalt concrete mix designs, and test track construction are discussed, as well as results of Heavy Vehicle Simulator (HVS) and laboratory testing. A number of problems were experienced during construction of the FDR-PC and FDR-EE lanes on the test track and consequently only the FDR-NS and FDR-FA lanes and one section of the FDR-PC lane (5 percent measured cement content) were considered satisfactorily uniform for the purposes of accelerated pavement testing. The FDR-FA and FDR-PC sections performed very well and testing on both was terminated long before the terminal rut of 0.5 in. (12.5 mm) or average crack density of 0.8 ft/ft2 (2.5 m/m2 ) were reached (no cracks were observed on either section). The two FDR-NS sections performed acceptably, with the section with the thicker asphalt surfacing (120 mm) outperforming the section with the thinner asphalt surfacing (60 mm), as expected. Terminal rut was reached on both sections, but no cracking was observed. The FDR-EE sections performed poorly, with terminal rut and terminal cracking both reached after a limited number of load repetitions. This poor performance was attributed to problems associated with construction, and consequently no conclusions can be drawn from the test results regarding this stabilization strategy. The advantages of using foamed asphalt with cement and cement only recycling strategies over recycling strategies with no stabilization are clearly evident from the results. A second phase of accelerated pavement testing, full-scale field testing, and additional laboratory testing are planned to collect sufficient data for the development of mechanistic-empirical design criteria (and revised gravel factors) for full-depth reclaimed pavements. However, there is sufficient evidence to show that pavements that are rehabilitated using full-depth reclamation strategies will satisfactorily withstand design traffic levels common in California. Rehabilitation using this approach is quick, has minimal disruption to traffic, reuses all materials, does not require removal of material from the site, and effectively replaces weak base layers, thus preventing reflective cracking that is common in more traditional overlay projects. Based on these conclusions, it is recommended that full-depth reclamation be promoted as an appropriate rehabilitation strategy in California. Future research on partial- and full-depth reclamation should be coordinated to facilitate consistent design and specification documentation, and to facilitate the preparation of a comprehensive guide covering all forms of pavement recycling.