Preventive maintenance, if performed before the road begins to break up, is the most cost-effective of the three programs. Its purpose is to extend the life of the road and to keep it looking and riding, as much as possible, in like-new condition. The work performed under the preventive maintenance program is called chip sealing, slurry sealing and resurfacing. The purpose is to stop water from entering the roadway, which causes early break up of the road surface. The useful life of roads can be extended from 20 to as much as 100 years if, on a regularly scheduled basis, small breaks are fixed and a seal coat or resurfacing is done before more severe damage occurs. This is the reason why maintenance work is sometimes done on streets, that appear to be in good condition.
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Chip Sealing - the application of crushed rock (gravel) over an emulsified asphaltic oil.
The oil seals the pavement from water penetration while the gravel provides a wearing surface to protect the oil seal from traffic. The oil is sprayed on the pavement first, immediately followed by replacement of gravel. Compaction rollers then go over the gravel to seat it in the oil. After a few days, power sweepers pick up any excess gravel. Another follow-up sweeping is done within one month to remove gravel loosened by traffic. Ideally, local streets should be chip sealed approximately every ten years.
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Slurry Sealing - a mixture of fine aggregate (sand-like) with emulsified asphaltic oil.
This mixing is done in a specially equipped slurry-seal truck, then the slurry mix is spread on the pavement. Slurry sealing is usually done on streets with higher traffic volumes and speeds because it provides a smoother ride and avoids the problems associated with flying gravel caused by higher speed traffic. Major streets should be slurry sealed approximately every eight years.
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Cape Sealing - a slurry seal spread over a chip seal.
The Cape Seal consists of two sealing layers. The first sealing layer (a chip seal) is an applcation of crushed rock over asphalt oil and the second sealing layer (called a slurry seal) is a finer mixture of sand and asphalt oil placed over the first layer that will help "lock" in the first layer of rock. Click here for 2011 Cape Seal Schedule.
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Resurfacing - the application of two to four inches of asphalt over an existing pavement to provide a smooth surface and add strength to the road.
On most of our resurfacing work, prior to placing the new asphalt, a specially designed polyester fabric is placed over the old road to seal the surface and prevent cracks from reflecting through the new asphalt. Major streets have priority for resurfacing because they serve the greatest number of people.
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For more information or to report a pavement problem call (408) 794-1900.
