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The objectives of this study were to document the performance of roads using full-depth reclamation (FDR) and stabilized FDR (SFDR) in Minnesota; help develop SFDR design parameters appropriate for Minnesota; provide information on FDR/SFDR design procedures and specifications from beyond Minnesota; share current Minnesota FDR practices; and catalog the characteristics of some FDR/SFDR roads. A comprehensive literature review of FDR/SFDR projects and case studies was conducted; and an online survey was distributed to Minnesota local road agencies to determine the stabilizing agents used for SFDR projects. Eighteen FDR/SFDR test sections from eight counties were then selected for a case study; and performance data and core samples were collected for the sections. Minnesota gravel equivalency (GE) analysis was performed to back-calculate the granular equivalent factor for FDR/SFDR layers based on the design equivalent single axle loads (ESALs) and R-values for subgrade soils. The back-calculated GE values indicate that designers have likely been using GE values for FDR/SFDR layers that are consistent with current recommendations. It is recommended that the current GE values be generally retained for FDR/SFDR design. However; when slower-moving vehicles are the critical design consideration; relatively robust performance of FDR/SFDR layers may be expected. Visual distress surveys indicated that the FDR/SFDR bases studied are performing well in terms of destroying crack patterns that are often reflected through traditional hot mix asphalt (HMA) overlays. Therefore; decision makers may want to consider the use of FDR/SFDR as a base for reasons other than structural capacity.

The objective of this project was to provide a better understanding of how various virgin aggregate and recycled asphalt pavement (RAP) mixtures for surface layers affect the performance of gravel or crushed rock roads and; with further analysis; to determine the optimal RAP content for Minnesota gravel roads. This project included a literature review; preliminary laboratory testing; economic and feasibility analysis; and two field studies. Several studies regarding the use of RAP materials for road surfaces were reviewed. Then; laboratory tests on various RAP materials; one virgin aggregate; and mixtures of RAP materials and virgin aggregate were conducted to observe the effect of RAP on the index properties of the materials and the engineering properties of the mixtures. Initially; six test sections were constructed with various surface aggregates in two locations. Virgin RAP-aggregate blends having 15% to 60% RAP contents were placed as surface aggregate. Then; three more test sections were constructed using RAP-aggregate blends having 50%; 70%; and 80% RAP contents. Several field tests; including lightweight deflectometer; dynamic cone penetrometer; scrape; and dustometer tests; were performed to evaluate the test sections. This report provides insights regarding the effect of using RAP material on surface layers to reduce the use of virgin aggregates. It was concluded that the optimal RAP content for unpaved road surfaces changes according to the properties of the materials used; testing methods; and site conditions.