The Transportation Engineering and Road Research Alliance and Road Dust Institute conferences are being jointly held this week in Minneapolis. Among the many research topics being presented are several recently completed studies funded by the Minnesota Local Road Research Board.

The LRRB, which celebrates its 55th anniversary this year, is one of only two statewide organizations in the United States that fund transportation-related research projects and education on behalf of local governments.  In honor of the TERRA and dust control events, we thought we’d take the opportunity to highlight a few of the latest pavement and dust control-related research projects from the LRRB.  If you’re at TERRA today, be sure to stop by their booth and check out their latest research results, videos and more.

Recycled Asphalt Pavement: Study of High-RAP Asphalt Mixture on Minnesota County Roads 

This report summarizes the field performance of local roads containing recycled asphalt pavement (RAP), associated field and laboratory work with asphalt activation, and design and performance testing of high-RAP bituminous mixtures. Conclusions include:
• Transverse cracking performance of county highways averaging 20 to 26 percent RAP was improved when PG 52-34 binder was used.
• Coarse aggregates from plant mixing achieved a more uniform coating and were subjected to less abrasion than those from laboratory mixing.
• IDT critical temperature results showed that the addition of RAP significantly increased the critical temperature, predicting less crack resistance.

Research using Waste Shingles for Stabilization or Dust Control for Gravel Roads and Shoulder

Minnesota generates more than 200,000 tons of shingle waste each year. While a small portion of recycled asphalt shingle waste (RAS) can be incorporated into hot-mix asphalt (HMA) pavement mixtures, there is still a lot of waste left over, prompting MnDOT to investigate other potential uses. Alternative options include improving the performance and quality of gravel surfacing and reducing dust by replacing common additives such as calcium chlorides with RAS. This will remove valuable RAS materials from the waste stream, supplement the use of more expensive materials, and improve the performance of local roads.

Aggregate Roads Dust Control: A Brief Synthesis of Current Practices

More than half of our local roadways are gravel roads, making them a vital part of our transportation system. One of the drawbacks and biggest complaints about gravel roads is the dust they produce when vehicles drive over them.  Residents that live on gravel roads deal with the dust that settles on their homes, yards, and parked cars. Dust can also have adverse effects on air quality and the environment. To help control the dust on gravel roads, the Minnesota LRRB has developed this new guidebook, which summarizes a variety dust suppressants, their effectiveness and impacts.