A Schwarze M6 Avalanche chip seal sweeping in the city of Minneapolis, MN.

A chip seal is a thin protective wearing surface that is applied to the pavement. A chip seal offers preventive maintenance from the effects of sun and water, both of which may deteriorate the pavement structure, and also makes it more difficult for water to enter the base material and prevents freeze-thaw damage for those locations with below freezing temperatures.

Chip sealing also increases the friction of the pavement, due to the addition of the cover aggregate. This makes the pavement less slippery and easier to stop on, particularly on wet pavement. A chip seal gives good, gripping texture to the pavement surface.

Traditionally, chip seals were thought of as most applicable to low volume, low-speed roads because they will eventually involve some amount of loose aggregate. On a high volume or high-speed road, this loose aggregate can be picked up and thrown by wheels, which can result in chipped paint and broken windshields. However, developments in asphalt cement modifiers and construction procedures have made it possible to use them on high volume/speed roads including interstates.

Chip sealing is cheaper than resurfacing an asphalt concrete or a cement concrete pavement, but not as long-lasting. A two to four-year service life is common.

Sweeping is done before a chip seal project, to ensure the roadway is thoroughly cleaned, and again at the completion of the chip seal process to remove surplus rock from the surface, typically a day later.

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