Rutting Specifications Development for FDR and the Potential for the HWTD to Replace the TSR.

Abstract: Currently, no limiting rutting value exists that can be used to assess FDR mix performance during the mix design phase. Furthermore, the FDR mix design uses the Tensile Strength Ratio (TSR) as a means for assessing the sensitivity of mixtures to moisture. However, the TSR test cannot precisely differentiate between mixtures likely to experience moisture damage and those that do not. To this end, this study has attempted to provide a limiting/maximum rutting value for an FDR mix using the Hamburg Wheel Tracking Device (HWTD) test. Besides, this study assesses whether the HWTD test can serve as a substitute for the current TSR test. Three types of FDR materials (FDR1, FDR2, and FDR3) were stabilized with 2.5% foamed asphalt and 1% Portland cement, and materials were collected from the roadway construction sites. In the laboratory, loose materials were compacted using a Superpave Gyratory Compactor (SGC) and tested in the HWTD. Based on the test results, the maximum rut values were determined. The test data were evaluated for Stripping Slope (SS) and Stripping Inflection Point (SIP). Next, the SS and SIP values were correlated with the TSR value. A poor correlation was observed, and therefore, it was concluded that the HWTD test could not be used as a substitute for the TSR test during the FDR mix design.