Common Asphalt Problems
Asphalt is a flexible-wear surface for vehicle traffic, and as such, is subject to damage and deterioration if not initially installed in a proper fashion and then maintained properly. You and your maintenance staff should be aware of how to deal with the following common types of damage.
Cracks. Surface cracks are often the first visible signs of underlying problems. Small cracks expand to form larger problem areas that have an "alligatored" appearance. Once this type of deterioration occurs, it is usually necessary to dig out the bad asphalt and install new sub-base and asphalt. Look for long cracks to appear where the seams were during initial construction. These are the weakest areas in the asphalt mat.
Cracks should be filled as soon as possible to avoid water infiltration and expansion. There are many types of crack fillers on the market, but we recommend that you use a hot, rubberized, crack-fill material. It will have better results penetrating the crack and will be less likely to fail because of its capacity to expand and contract.
Water Damage. Water is probably the most significant in the premature wear and/or deterioration of asphalt surfaces. Although surface water, or "ponding," is not desirable, it is usually subsurface water from adjacent areas that creates the worst damage. Many times water will flow up through cracks that have developed in the asphalt and over time will cause the asphalt base and eventually the asphalt itself to deteriorate.
Patching the asphalt in this situation will not last because the crushed stone base beneath the asphalt is saturated with water and no longer provides a solid foundation for the asphalt surface to rest on. This type of problem will grow larger and at a rapid rate if not completely dug out and if the underlying water problem is not eliminated. Water can be re-routed through the installation of underground French drains, which capture the water and provide another path for it. Once all of the subsurface water problems are corrected, you will be ready to begin repairs to the crushed stone sub-base material and asphalt.
It is generally a good idea to make repairs with a heftier specification than originally existed. For example, if the failed asphalt comprised one three-inch layer over approximately three to four inches of crushed-stone base, it would be wise to increase the repair specification to include one layer of asphalt four inches thick over a six-inch crushed-stone base.
When there is only minimal failure of the stone base material you may choose to overlay the existing asphalt with a new course of asphalt. When this method is used it is critical that all cracks are properly cleaned and filled prior to the overlay of new asphalt. When the cracks are severe or are widespread it is also common to install a paving fabric over the existing asphalt. This helps to eliminate or prolong the time that the existing cracks work their way back through the new asphalt.
Oil/Gasoline Spots. Oil and gasoline leaks from vehicles can cause premature deterioration of asphalt and asphalt sealer if not properly addressed. Do not blowtorch oil spots. This only breaks down the oils in the asphalt and makes it more susceptible to future-deterioration. Instead, remove oil spots with an absorption compound. Before applying new asphalt or sealer, all oil spots should be pressure washed with a mild detergent and then primed with an oil-spot primer. This will prevent the oil or gas from bleeding through the new sealer as quickly and in some cases may prevent future problems.
Importance of Seal-Coating
The best way to prolong the life of your asphalt, especially in high-traffic areas where wear and tear have exposed the aggregate stone, is to apply a sealer on a regular basis. Seal-coating every two to three years will help prevent surface deterioration. The sooner asphalt is sealed after its initial installation the better. New asphalt should be sealed six months to a year from the date of installation. This gives the asphalt time to cure but seals in the oils and tars that give asphalt the flexibility to withstand traffic and the elements.
Proper Preparation is Important. No sealer is a substitute for major asphalt repairs, and sealer will not adhere to dirty or oily surfaces. Make sure that the asphalt is properly repaired and cleaned prior to application.
Clean the asphalt by using forced air and sweep it with wire brooms. This will loosen dirt and debris lodged in the pores of the asphalt that might cause the sealer to fail. Pressure washing may also be necessary in areas with a heavy-build up of dirt or oil spots. Most manufactures also recommend a primer coat prior to standard two-coat sealer application. Ensure sealer quality. There are many types and grades of asphalt sealers on the market today, but the most reliable ones are those made with coal-tar emulsions. These sealers are impervious to gasoline and oil and do not breakdown when exposed to ultra-violet radiation. Most of the higher quality sealers are mixed with special additives that allow them to cure more rapidly.
As with any other coating, sealers are easily modified after purchase. Therefore it is important that you verify that the sealer being applied on your property has been mixed with the proper ratio of sand and water. Unfortunately, some contractors water down sealers or add too much sand prior to application, causing poor adhesion and/or premature wear.
The Application Process. All sealers must be mixed and installed in accordance with the specific manufacturer's recommendations. Ask the contractor to supply you with this information prior to application and have someone in your organization make sure all specifications are being followed.
Pay attention to the weather conditions during the application process. High humidity and rain will slow down the curing process and could cause uneven distribution of the material. Likewise, warm temperatures and good exposure to the sun will accelerate the curing process.
As a rule of thumb, a minimum of 24 hours curing time should be allowed between each coat of sealer and after the last coat is applied. Additional time may be required depending on the weather.
Asphalt is a wearing surface that is exposed to the elements and therefore requires on-going maintenance to prevent premature deterioration. All asphalt should be inspected at least annually. The cracks should be filled with a top-quality, hot crack-fill material, and large areas of asphalt failure should be removed and replaced continually. This type of preventive program is relatively inexpensive and will prolong the life of your asphalt.