Minnesota Department of Transportation
Minnesota has a large network of aggregate roads. The majority of the system is maintained by counties and townships. Some of the aggregate roads need to be upgraded with a sealed surface for dust control or to provide a smoother driving experience, as well as for local economic development. Local road officials are often faced with the responsibility of upgrading the roads with a limited budget. Light surface treatments (LSTs) are considered an economical alternative to the conventional upgrade approaches using hot-mixasphalt (HMA) or concrete pavements. The currently used methods in Minnesota for the structural design of LSTs for aggregate roads were originally developed for structural design of flexible pavements. This research evaluated the design methods that can be used to design LSTs for aggregate roads. The methods evaluated include the MnDOT granular equivalent (GE) method and the MnDOT mechanistic-empirical method (MnPave design software), which are used in Minnesota, and the American Association of State Highway and Transportation Officials (AASHTO) flexible pavement design method and South Dakota aggregate road design method, which are practiced in other places in the United States. The results include a discussion of the applicable situations for each method. The research team also conducted a survey that was distributed to the county engineers in Minnesota to document their experiences with LSTs. Recommendations for improving the current design methods when applied to LSTs on aggregate roads are suggested based on the survey results.
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