Iowa’s unpaved roads are essential for keeping rural communities connected and agricultural products moving. National Farm Safety and Health Week – which will take place this year from September 18-24 – is the perfect time to highlight Iowa DOT Research’s efforts to increase the roads’ safety and durability.
These roads are designed to have a thick aggregate top layer, but heavy equipment and extreme temperature fluctuations can break down the materials on the surface and cause potholes and other distresses to form prematurely.
Engineers have long known that keeping the aggregates in place is key to longer-lasting roads, but finding a solution that’s both economical and environmentally friendly hasn’t been easy.
Quarry fines—the small particles left after larger rocks and materials are removed from a quarry—are both cheap and plentiful.
To learn whether adding these fines to the aggregates on a road’s surface would help the road last longer, researchers evaluated various fines and aggregates in the laboratory to find types that interlock well together and identify the ideal proportions of each for a successful mixture. The researchers then constructed seven test sections on unpaved roadways that experience heavy equipment traffic, using fines from five quarries across the state. Through a variety of durability tests and comparisons with two control sections, the team evaluated the fines’ impact on the performance of each section over several seasonal freeze-thaw cycles.
The efforts showed that while all five types of fines worked well to keep the surface aggregates in place, local road managers will need to carefully consider a number of factors, including the costs to buy the materials and haul them to the jobsite, to determine if adding waste quarry fines makes sense for a specific project.
Learn more about this project in the new research brief from Iowa DOT.