Performance Comparison of Recycled Pavement Foundation Layers

Abstract

This paper describes results from a study comparing the performance of side-by-side test sections of pavement foundation layers constructed with on-site recycled materials and surfaced with hot-mix asphalt (HMA). Test sections included recycled materials blended with subgrade to create a mechanically stabilized subgrade layer and recycled materials placed in an overexcavated subgrade layer. In situ falling weight deflectometer (FWD), dynamic cone penetrometer (DCP), and laboratory freeze–thaw tests were used to assess the performance of the test sections, in comparison with a control section where recycled materials were not used. Field testing was conducted at seasonal intervals over 2 years after construction, and the results were statistically analyzed with two-tailed Welch's t-tests to account for unequal variances. Findings indicated that test sections with on-site recycled materials provided improved support conditions for the pavements during both before and after freeze–thaw conditions, when compared with the control section. FWD and DCP test results indicated that recycled material blended with sub-grade showed more thaw-weakening compared with recycled material alone. Laboratory freeze–thaw test results corroborated the comparisons observed in the field test results. Correlations between FWD test measurements on the foundation layer and on the pavement yielded a statistically significant regression relationship, which indicated the importance of support conditions on the surface layer performance. Analysis of bid prices to construct the test sections indicated no statistical evidence to suggest that the unit costs for the test sections were different from one another.