Design and Construction of NDOT Test Sections on Interstate 80
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Four test sections were constructed on 1-80 east of Reno, Nevada during the month of September, 1998. The sections are located in the travel lane ofthe westbound direction of 1-80. Two sections were designed with the Superpave volumetric mix design method and two sections were designed using the Hveem design method. Two different binders were used: AC-20P and PG64-22. The PG64-22 binder is a neat asphalt binder similar to one used on Westrack. Each binder was used with a Superpave designed mix and a Hveem designed mix which resulted in the four sections labeled as: SPAC-20P, SPPG64-22, NVPG64-22, and NVAC-20P. All four sections are placed in series to be evaluated under similar environmental and traffic conditions. The Superpave mix designs were conducted in the University ofNevada's Pavements/Materials Laboratory while the Hveem mix designs were conducted in the NDOT's Materials Division Laboratory. Materials testing and evaluations were conducted before, during and after the construction activities. Aggregates, binders and mixtures were tested for their conformance with the Superpave and Hveem mix design specifications. Based on the testing data it was concluded that the asphalt binders used on the test sections consistently conformed to the specified grades throughout the entire construction activities. The hot mixed asphalt plant used by Granite Co. (Lockwood Plant) was not capable of controlling the amount of bag house materials being returned into the mix. The Superpave volumetric mix design is not capable of estimating the optimum asphalt binder content based on the volumetric properties of the mix at a given asphalt binder content. The in-pace compaction data indicate that the Superpave mixtures with both the AC-20P and the PG64-22 binders experienced some tenderness and were moving under the roller. This behavior ofthe Superpave mixtures has resulted in two problems: a) additional roller passes were needed to achieve a constant density, and b) the bottom lift became over-compacted as the top lift was being rolled.