Asphalt cement is susceptible to oxidation due to it's organic nature and exposure to environmental elements. During the oxidation process the asphalt cement becomes dry and brittle, thereby losing it's flexibility. As the flexibility of the asphalt is lost, traffic loads cause small cracks to occur which with continued loading become larger and result in pavement failure. To slow down the effects of oxidation, asphalt pavements with medium to high severity polished aggregate at the surface or with high void contents should be treated with a seal coat. Typically seal coats may be needed after the pavement has reached an age of 1 to 3 years.
A seal coat is a thin asphalt surface treatment used for preventive maintenance. Seal coats do not repair structural problems and are not able to increase the structural strength of a pavement. Examples of seal coats include fog seals, slurry seals, micro-surfacing, and chip seals. Seal coats placed over existing cracks will typically not prevent the existing cracks from reflecting through the seal coat in a short period of time.
With age, if cracks develop in the pavement they should be sealed to prevent water infiltration. Pavement deterioration can increase exponentially if cracks are left unsealed providing avenues for water infiltration. Water infiltration weakens the pavement, stone base and subgrade making it more susceptible to failure under traffic loading.
Cracks ranging in width from 1/4 to 3/4 inch should be blown out with compressed air, cleaned of debris and vegetation, and filled with a rubber asphalt sealant. A backer rod may be installed for wider cracks.
Cracks greater than 1 inch in width should be blown out with compressed air, cleaned of debris and vegetation, and filled with fine graded hot mix asphalt (sand asphalt mix) or an asphalt emulsion slurry.