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    Warm Mix Asphalt

    Warm Mix Asphalt (WMA) allows for asphalt to be produced and placed on roads at lower temperatures than the traditional hot mix method. WMA is a Federal Highway Administration (FHWA) Every Day Counts Round 1 (EDC-1) innovation that Pennsylvania championed. 

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    A dump truck unloading material at a roadway construction site.

    How Does It Work? 

    Less energy is needed to heat the WMA mix and less fuel is needed to produce it. Advances in WMA have reduced the thickness of the binder so that asphalt aggregates can be coated at lower temperatures. The key is the addition of additives (water-based, organic, chemical, or hybrids) to the asphalt mix. The additives allow the asphalt binders and asphalt aggregates to be mixed at the lower temperatures. Reducing the viscosity also makes the mixture easier to manipulate and compact at lower temperatures.

    What Are The Benefits? 

    PennDOT uses WMA because of its environmental and pavement-quality benefits. By using lower temperatures than traditional asphalt, WMA reduces fuel consumption and reduces emissions. This enhances worker safety, reduces pollution and extends the paving season. It also reduces paving costs by decreasing time and labor spent compacting the mix and improves asphalt compaction by providing proper mixture density.  

    Did You Know?

    • Fuel consumption during WMA is typically reduced by 20 percent. 
    • WMA production methods use temperatures 30 to 120 degrees Fahrenheit lower than traditional hot-mix asphalt. 

    Innovation in Motion  

    Per Publication 408, PennDOT requires the use of WMA on all asphalt paving projects. In addition, PennDOT works with local governments to provide training and funding to encourage the use of WMA on local roads. For example, WMA is eligible for Municipal Liquid Fuels Funds, an important funding source for local transportation projects. Information about the Municipal Liquid Fuels can be found on PennDOT’s Local Technical Assistance Program website.