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Road Pavement Treatment Types
Sonoma County's Pavement Preservation Program makes use of several specialized techniques in response to the type of degradation observed on the road's pavement. Different types of degradation need different treatment techniques.
Asphalt Concrete Overlay
Asphalt Concrete (AC) consists of mineral aggregate bound together with asphalt, laid in layers, and compacted. The most common type used on streets and highways is Hot Mix Asphalt (commonly abbreviated as HMA).
Hot Mix Asphalt Overlay is regarded by most road departments as a standard for road maintenance and restoration, and has been for several decades. It produces durable, long-lasting results, and can increase pavement life by 15 years or more. Combined with other processes, such as milling or grinding of old pavement, an AC overlay can transform a tattered road surface into a like-new condition.
A Chip Seal is liquid asphalt is sprayed onto the pavement followed immediately by spreading on a thin layer of uniformly sized aggregate chips. The new surface is then rolled to embed the chips in the asphalt. Once the asphalt has cured (usually taking about 24 hours or less) any loose chips are swept up.
Chip seals are relatively inexpensive, as compared to conventional hot mix asphalt overlays, and are fast and easy process (usually completed in 24 hours or less). A chip seal can extend pavement life by 5 to 7 years.
Cold-In-Place Recycling (CIR)
Cold-in-Place (CIR) recycling is a method of removing and reusing the existing asphalt surface. It involves grinding off the top 2 to 5 inches of the existing asphalt surface and mixing the crushed asphalt with an asphalt recycling agent, and placing it back down with a paver.
Bonded Wearing Course
A Bonded Wearing Course (BWC) is a thin, Hot Mix Asphalt Overlay placed over a polymer modified emulsion membrane which, combined, seals the existing pavement and bonds the two surfaces. Application of both materials is done in one pass using a single machine. The finished result is considered a high-performance surface course for preventive maintenance or new construction over either asphalt or concrete pavements.
A bonded wearing course is relatively fast process, done using a single machine. If used correctly, it can extend pavement life 10+ years, and cost less than conventional AC overlay.
A fog seal is a light application of a diluted slow-setting asphalt emulsion to the surface of an aged pavement surface. Fog seals are low-cost and are used to restore flexibility to an existing asphalt pavement surface.
Full-Depth Reclamation is a type of complete road reconstruction where the old pavement and base materials are not removed. Instead, they are processed on-site. During this process, the old materials are pulverized, mixed, and treated with a stabilizing agent (such as cement or asphalt emulsion) to produce a like-new road base. Typically, the roadway is then re-surfaced with an overlay of new asphalt.
There’s no need to haul in aggregate or haul out old material for disposal. Truck traffic is reduced, and there is little or no waste. Due to reduced transportation, costs far less than the conventional approach to reconstruction. Can provide up to 30 years of additional life.
A slurry seal is the application of a mixture of water, asphalt emulsion, aggregate (very small crushed rock), and additives to an existing asphalt pavement surface. A slurry seal is similar to a fog seal except the slurry seal has aggregates as part of the mixture.
A cape seal is a combination of treatments, it is a chip seal followed by a slurry seal or a micro seal.