Asphalt maintenance can be categorized into five areas: patch repair, asphalt overlay, inlay, pulverize in place and seal coating. It is important to understand the primary cause of asphalt failure is penetration of water into the asphalt base. Assuming the initial pavement was designed and constructed properly, the process of oxidation begins shortly after the asphalt has been placed. Over time, it becomes dry and brittle and the aggregate starts wearing away, causing cracks that allow water to penetrate into the base of the pavement. As water seeps into the cracks, the base material moves and settles, leading to further "alligatoring," or surface cracking in a grid-like pattern. When the pavement reaches this stage, the only options are patch repair or replacement of the old asphalt.
Patch repair, the most common form of pavement maintenance, deals with isolated areas. The pavement is removed from these areas by saw cutting and backhoe, or by the use of a grinding machine. It is then replaced with new asphalt. The amount to be removed is determined by the removal method. Ask your asphalt-maintenance contractor how deep the pavement replacement should go and whether the base rock should also be replaced.
In most cases, the removal depth should be equal to 1.5 times the original pavement thickness. Replacing the asphalt at the original thickness does not make sense if the pavement has failed in this area before. If no base rock exists in the entire roadway, adding it to the patched area is not a good idea. If base rock exists in the roadway but the thickness was deficient in the failed area, you should replace the base-rock section to match the adjacent areas. This will allow for a more uniform base support and, ultimately, a longer-lasting roadway.
Also, a good rule of thumb when laying out patchwork is to extend the amount of removal to 12 inches beyond the failed area. Remember, squares and rectangles are best. Irregularly shaped patches with multiple angles create weak points and should be avoided.
Asphalt overlay is an affordable method of pavement repair that provides a new wearing surface of asphalt over the entire road. The most common factors you should be aware of when dealing with an overlay are:
Overlay thickness: The minimum should be 1.5 inches, while the maximum should be 2.5 inches.
Reinforcing fabric: The use of reinforcing fabric has garnered a lot of attention lately. A problem with the fabric's use is its disposal during inevitable asphalt-patch repairs or removal. Most failed pavements are sent to a recycling plant to be processed into recycled base rock. The presence of reinforcing fabric prohibits asphalt from being recycled; this results in increased dumping costs because fabric-reinforced asphalt is only accepted at landfills. Many overlays are being engineered without fabric. Instead, an additional half-inch of asphalt is being used. Thinking of future costs is never a bad idea.
Smooth transitions: When considering where to grind down the existing pavement, remember this: You do not want the contractor to reduce or feather down your overlay section to match an existing structure. This severely weakens the strength of the overlay. To prevent this, have the existing pavement ground down at all gutter lines, concrete driveways and any slabs where the new overlay must meet flush.
Utility lids: You have two options when dealing with utility lids. Most utility boxes have riser rims that can be fitted on the manhole or valve box and adjusted for height. This is the easiest way to raise lids, but often the results are not perfect because of surface deviations. The best way to raise your utility lid is by removing the existing frame for the lid, blocking it up to the new roadway elevation and securing it with a 12-inch collar of concrete. This concrete can then be capped with a thick lift of asphalt to match the roadway surface.
Inlay and Pulverize in Place
Both inlay and pulverize in place are accomplished with the use of a milling machine. The inlay process removes a specified depth of the existing asphalt roadway--often a previous overlay. This allows contractors to put the roadway back at the pre-inlay elevation. In some cases, it is important to maintain good drainage. After multiple overlays, the roadway often becomes too high.
The pulverize-in-place method actually reduces all of your roadway asphalt to base-rock-size particles. The resulting product can be graded like new base rock and the roadway reshaped for improved drainage. The material is then moisture-treated and compacted, and a new lift of asphalt is placed. The benefits are there are no export material costs and the roadway can be reshaped to match new and existing structures. If a reinforcing fabric is encountered at either of these processes, additional costs will likely be incurred.
Seal coating is an important tool in extending the life of pavement and should not be overlooked. Seal coats generally consist of a mixture of emulsified asphalt, water, mineral fillers and various other admixtures. The process seals the top of the asphalt, preventing water from penetrating the surface of the pavement and protecting the top layer of asphalt from oxidation and wear caused by exposure to the sun. Seal coats also provide a smooth, black, even surface. Good looks are an added benefit, but seal coating is not just for aesthetics--it will actually extend pavement life.
A seal coat should be applied to new pavement every six months to one year. Future applications of seal coat should be applied at intervals of three to five years, or at times when roadway aesthetics are not up to par with the balance of the community. The thickness of the wearing surface will depend on the number of coats applied and the amount of water added by the contractor. Remember, seal coat is water soluble, so it is important to deal with reputable contractors in the asphalt-maintenance business.
Todd Slyngstad is owner and president of Silicon Valley Paving Inc., a licensed, bonded and insured asphalt-maintenance contractor based in San Jose, Calif. For more information, contact the company at P.O. Box 26558, San Jose, CA 95159-6558; or visit www.svpinc.com.
Speed bumps are critical for providing a safe environment on the internal roadways of a self-storage property. Their importance in controlling the speed of traffic throughout the facility should not be underestimated. The owner or manager should discuss the traffic flow with an asphalt contractor to determine the best locations to place the speed bumps.
There is no specific quantity or size that is considered a standard for self-storage facilities. However, I recommend a 24-inch-wide by 3-inch-high speed bump that runs the width of the road as a standard size. The traffic flow and speed restrictions will also help determine the proper size. The speed bumps should always be striped--with yellow or white paint diagonally striped--or painted solid. The intent is to get the attention of the driver and let him know a speed bump is ahead. Sometimes a stencil is placed on the asphalt before the speed bump to warn drivers before they reach the bump. In areas where the lighting is poor at night, it is recommended to place reflectors on the speed bumps or use glass-beaded paint that bounces off headlight beams.
Speed bumps require no additional maintenance--they are the same as the surrounding asphalt. They should be seal coated to protect the asphalt and restriped as the paint fades.