Better Roads

Photo courtesy of FHWA Mechanistic-empirical pavement design considers site conditions such as traffic, climate, subgrade, existing pavement condition for rehabilitation, and construction conditions, in proposing a trial design for a new pavement or rehab; then, using software, the trial design is evaluated through prediction of key distresses and smoothness. ison, for the National Center for Freight and Infrastructure Research and Education – found the MEPDG had limitations in that it did not account for the effects of supplementary cementitious materials on the pavement design, and it er- roneously restrained the permissible range for concrete modulus of rupture input due to thermal stress on jointed plain concrete pavement. ME principles are being adopted in other ways. For example, as of October 2012, the Minnesota DOT permits the ACPA's StreetPave software to be used for jointed concrete pavement design as an alternative to its existing MnDOT RigidPave software, with the exception of concrete pavement projects within trunk highway rights-of-way, which must continue to use RigidPave. That's significant because the design method used in StreetPave is based on the Portland Cement Association (PCA) thickness design method, incorporating results from the empirical 1954 AASHO Road Test, more recent information from mechanistic-empirical studies, and a newly updated fatigue model, MnDOT says. Perpetual Pavements The asphalt perpetual pavement reflects mechanistic design, but also is suited for long-term pavement preservation, as the design calls for deep, robust, fatigue crack-resistant layers of asphalt, of different mix formats, topped with a sacrificial friction course that can be periodically milled and overlaid, likely at night to reduce impact to motorists. Text INFO to 205-289-3789 or visit www.betterroads.com/info Untitled-13 1 RoadScience_BR0813_old.indd 11 Better Roads August 2013 11 6/26/13 8:57 AM 8/1/13 10:55 AM

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• BETTER Bridges: Big River Bridges Getting Smarter: The four bridges that span the Mississippi River to join Mississippi to Arkansas and Louisiana are getting major Intelligent Technology System upgrades to make them safer and to improve traffic management
• ROADSCIENCE: A Good, Long Life: In Part IV of our series Building Roads that Won't Fail, Tom Kuennen looks at some of the tools that civil engineers can use to design pavements that keep performing as they should over the longest time possible. Such thin
• APPLICATIONS & INNOVATIONS: Managing Winter: It's year-round job, but now is one of the most important periods in making sure your winter months will be safe and productive. FMI's Brian Moore says managers now should be focused on a few key areas that can
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