Kent County Road Commission Blog

Category Navigation

Why Are You Putting Tar and Gravel on Paved Roads?

Why Are You Putting Tar and Gravel on Paved Roads?

Just as our own skin protects our bodies from harsh elements that can compromise our health, the surface layer of a road protects the integrity of the layers beneath. That is why road surfaces are designed to receive periodic treatments to protect the integrity of the multiple layers of material.  One of the best ways to extend the life of asphalt pavement is to apply a cost-effective preservation treatment called Chip Seal.

Chip seal is applied to roads with asphalt pavement surfaces throughout their life cycle. It can be applied one to three years after the completion of a reconstruction or resurfacing  project to protect the investment or to roads showing signs of deterioration. These roads first undergo the appropriate maintenance treatment – like a spot mill and fill or crack sealing - to restore the integrity of the road. Then chip seal is applied to protect the road’s surface and prolong its service life.


What is it?
Chip Seal is a pavement surface treatment that combines a layer of asphalt with a layer of fine aggregate to provide a high friction-wearing surface over old pavement.

How is it applied?
Prior to chip sealing a road, road damage like potholes and cracks are repaired by KCRC crews. In addition, low hanging branches and overgrowth may be trimmed. An application of asphalt emulsion is then sprayed onto the road surface, which is then covered with pea-sized stone aggregate. Rollers follow to embed the crushed aggregate into the emulsion. After the Chip Seal cures (approximately 1-2 months), a Fog Seal will be applied. This application helps to significantly reduce tire noise, eliminate dust, and bind the remaining aggregate into a smooth, black, hard-wearing surface.

What are the benefits to chip sealing?
Chip Seal can extend pavement life by 5-7 years. It also increases the “friction factor” of the roadway surface, helping to reduce the number of wet and snow-related vehicle accidents. It is cost-effective, allowing KCRC to treat twice as many roads when compared to the next lowest-cost surface treatment.

What are the challenges?
Chip seal application is typically applied from June to August because it requires warm, dry conditions. It is restricted by precipitation; inclement weather will delay application. After chip seal is successfully applied, a certain amount of aggregate will work loose during the curing process (approximately 1-2 months), and there can be dust post-application. 

What to Expect: The Chip Seal process is generally accomplished in one day, and intermittent lane closures are often used to allow drivers access. Post application, the new surface can be driven on almost immediately, but because of the emulsion and loose aggregate slow speeds are required. After the Chip Seal process, excess loose aggregate is swept off the roadway by mechanical sweepers. The roadway surface will continue to improve as the surface stabilizes, resulting in a stronger more durable surface. After the Chip Seal cures (approximately 1-2 months), a Fog Seal will be applied.