Pavement Preservation Program: Pavement preservation is a planned system of treating pavements at the optimum time to maximize their useful life, thus enhancing pavement longevity at the lowest cost.  It is a preventative maintenance program, not a construction project.  Below are just a few ways we use to preserve the road system.

Pavement Preservation Brochure     /     Chip Seal fact sheet     /     Microsurfacing fact sheet

Chip Seal: "Chip Sealing" is a common pavement preservation practice that extends pavement life and provides a good driving surface.  Since some St. Clair County Road Commission residents may not be familiar with the chip seal construction method, this fact page answers some frequently asked questions.

How are Chip Seals Different from Asphalt Overlays?
The difference is in the construction method.  Hot Mix Asphalt pavement is produced by heating liquid asphalt and mixing it with aggregate, with the mix then spread and compacted to form a durable road structure and riding surface.  Chip Sealing uses the same ingredients as asphalt concrete paving, but the construction method is different.  With chip seals, a thin film of heated asphalt liquid is sprayed on the road surface, followed by the placement of small aggregates ("chips").  The chips are then compacted to orient the chips for maximum adherence to the asphalt, and excess stone is swept from the surface.  The ingredients of hot mix asphalt and chip seals are the same; only the construction methods are different.

Why use Chip Seals?:  

1. Chip seals provide the St. Clair County Road Commission with the opportunity to maintain the roads for very low cost.
2. A chip seal is about one fourth to one fifth the cost of a conventional asphalt overlay.
3. By extending the time between asphalt overlays, chip seals result in lower costs over the long term.
4. By placing a chip seal sooner than an asphalt overlay would be placed, the traveling public benefits from roads maintained in better condition.
5. Chip Seals eliminate the need to crack seal.
6. Chip seals enhance safety by providing good skid resistance.
7. Chip seals provide an effective moisture barrier for the underlying pavement against water intrusion by sealing cracks in the pavement.
8. Chip seals prevent deterioration of the asphalt surface from the effects of aging and oxidation due to water and sun.
9. The St. Clair County Road Commission has successfully used chip seals for over 25 years to maintain roads.
10. Chip seals are used only on low traffic routes, less than 2500 vehicles per day.
11. Chip seals virtually eliminate black ice.
12. In hot weather, chip seals re-seal cracks by flowing back together.

Microsurfacing: Microsurfacing is a protective process which extends the life of pavement.  It is a thin, tough layer of asphalt emulsion blended with finely crushed stone for traction. 

This is a cost-effective method to renew the road surface and seal minor cracks and other irregularities.  This preventive maintenance process protects the pavement from moisture penetration and oxidation.

Similar to painting a house, microsurfacing creates a protective layer which preserves the underlying structure and prevents the need for more expensive repairs in the future.

Flexible pavements (typically asphalt) need periodic resealing to protect them from the deteriorating effects of water (rain) and sun.  If left untreated, the surface becomes brittle and may crack and ravel.  Periodic resealing prevents more extensive and costly repairs.  Regular preventive maintenance is the most  cost-effective way to maintain streets.

The Microsurfacing Process

Microsurfacing is a process similar to a slurry seal.  A mixture of asphalt emulsion and aggregate (crushed stone, gravel and sand) is applied to the road.  However, unlike slurry seal, microsurfacing uses emulsion that is modified with polymers and other ingredients so it cures more quickly. 

As the microsurfacing equipment moves along the street, the mixture is fed into a spreader box.  The material is spread across the full width of a traffic lane and then smoothed by a squeegee.  The equipment also feathers the edges for a smooth transition.  All this happens in one step.  After the microsurfacing seal coat cures (hardens), the street can be reopened and used normally.


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