Asphalt is the material of choice for homeowner association roads and parking lots. It’s a mix of about 92 percent stone aggregate and mineral filler combined with 8 percent asphalt binder. This combination allows it to stay in place and repel water. Because it stays dry, it has the strength to carry traffic loads and lasts a long time. It does, however, have drawbacks:
Poor resistance to the sun, salts and chemicals -- Asphalt is a complex mix of thousands of chemicals with predominantly open chain molecules with a high degree of double bonding. Open chained molecules provide easy access for sun, salts, and chemicals which breaks them down and destroys their binding and waterproofing properties. The visual indicator of this breakdown is the change of color from dark black/brown to gray.
Poor resistance to petrochemicals -- Asphalt is the heaviest and final component of petroleum distillation. The distillation process separates the asphalt from other byproducts like gasoline and oil. Since these byproducts are similar in molecular structure, they easily dissolve chemicals in asphalt.
The drying process -- As unprotected asphalt ages, the oils migrate to the surface and are burned off. The pavement eventually hardens and shrinks producing hairline cracking. Cracking allows water to penetrate the water repellent barrier to the ground below which, in turn, causes ground swelling and sinking which causes more damage to the asphalt. Advanced deterioration causes "alligatoring" (cracked surface area resembles an alligator’s back), heaving, sinking and disintegration.
Pros and cons of traffic -- Major roads have an advantage over homeowner association streets and parking lots because of heavy traffic which continuously "kneads" the oxidized surface back into the pavement bringing up fresh material. After the asphalt binder is exhausted, major roads are either overlaid with fresh asphalt or the pavement is completely removed and reinstalled. Low traffic HOA asphalt does not receive the same traffic loads and must apply different maintenance techniques to preserve the asphalt.
Sealcoating (aka slurry coating) is recommended. Sealcoating uses refined coal tar, a byproduct of coal being converted to coke in steel mills. Coal has different origins than petroleum so has different properties than asphalt. It has a much more stable molecular structure that is resistant to weather and chemicals. Coal tar is mixed with clay, mineral fillers and water to produce an emulsion, or slurry, which is easily applied to the asphalt. The mineral fillers give it durability. The coating is both flexible and protects against weather, sun and chemicals.
Sealcoating should be applied even to new asphalt since asphalt begins to oxidize immediately after installation. Thereafter, recoating should occur about every five years (sooner in high traffic areas). Major cracks should be sealed and spot pavement repairs made before each sealcoat application. If sealcoating is done as recommended, the life of the pavement can be extended by up to 300 percent. It also leaves a satin black finish which adds to the beauty and value of the property.
Clearly, asphalt maintenance should be a high priority in every homeowner association that has it. Do your community a favor and contact a qualified paving contractor today for an evaluation. Remember, it’s not your fault, it’s asphalt.