Chip Seal on High-Volume Roadways

Updated: 12/10/2014 5:29 PM
Created: 08/13/2014 5:02 PM
By: Julie Kruse

You might have noticed driving near Cloquet or on Highway 53 in Canyon the black, bumpy road surface rather than the grey smooth asphalt we're used to. If you are wondering what it is, it is called chip seal and it is not new to Minnesota.

Traditionally, it has only been used on rural or low-volume roads; however, MnDOT said it is now coming to busier roadways.

The only difference of chip seal from asphalt overlays is the construction method. It actually uses the same ingredients as concrete paving; however, a chip seal is about one-fourth to one-fifth the cost of conventional asphalt and extends the life of asphalt pavement by 5 to 7 years.

As for the loud noise it makes, MnDOT Pavement Engineer Rod Garver said it will eventually become quieter.

"Over time, because of the action of the plow, some of the stones will get knocked loose or forced down to the underlying asphalt layer," said Garver. "The amount of noise you hear in your car when you're driving a long time will mellow out."

The black bumps are small aggregates, or chips, that are adhered to the asphalt. They protect the pavement from the effects of sun and water, increases skid resistance and fills small cracks and other defects.