To understand asphalt pavement maintenance procedures one should first understand what an asphalt pavement is, how it is made, how it is installed and how it ages. Asphalt paving mixtures are all basically similar. They are comprised of aggregate (rock), fines (sand) and a small amount, typically five to six percent, of asphalt oil (AC).
Various quantities of these components are blended at high temperatures to manufacture the paving material. They are then transported to the job site, run through the paving machine and compacted to provide a smooth wear surface. Left alone and not properly maintained, the aggregate and sand are not affected appreciably by aging. But the oil or asphalt cement that binds the mixture together starts to break down or age as soon as this oil is exposed to heat when its being mixed. Further exposure to air, water and sunlight combine to cause oxidation, the aging process of asphalt. More importantly, oxidation ages the oil that holds the aggregate and sands together to form a flexible asphalt pavement.
The asphalt oil is made up of asphaltenes and maltenes. The asphaltenes
fibrous, graphite-like materials in the oil that do no break down or
The maltenes are the tacky, glue-like materials in the oil that effectively
together the aggregates and sands. The maltenes are the portion of the oil
that degrade and oxidize from the pavement.
Sunlight (UV) fractures the maltene molecules and they discharge from the
pavement. This is represented in the graying out of the pavement surface.
this process, the oil is losing its ability to bind the surface fines or
materials that provide the smooth texture of a pavement. These fines will
from the surface as it is exposed to water. The next step is that the
itself begins to pop out of the pavement leaving you with a gray, pitted and
brittle pavement surface.
Water-based coal tar emulsion coatings, or sealcoats, are commonly placed as a pavement maintenance procedure. This has been a standard practice and it was thought that sealcoating would protect a pavement from oxidation and fuel spill or water damage. These claims of protection are simply not true.
Although aesthetically pleasing when initially placed, these coatings are
very short lived. They wear off under traffic and it has been determined
government that these sealcoats will crack. Cracking in the coating
allows contaminates as well as the oxidizing factors to permeate the seal and damage the pavement.
A sealcoat will do nothing to replace low maltenes or restore
flexibility to an aging asphalt. Simply put, placing a coating on your
will not extend the life of that pavement, or postpone overlays or
Let us now introduce you to a treatment that provides unparalleled protection to a pavement from oxidation and water or fuel-spill damage. This treatment will also put back maltenes lost through oxidation. Better put, this treatment will not only stop oxidation (the aging of asphalt), but will reverse it, putting life back into the pavement, therefore extending service and postponing overlays or reconstruction.
The product that does this is Pavement Dressing Conditioner (PDC) Asphalt Rejuvenator. PDC is specified by the Federal Department of Transportation as a coal tar sealer/rejuvenating agent. This material is designed to penetrate into an asphalt oil, providing a fuel and water resistant surface. Now the source of protection for your coal tar is in the pavement, not just on it.
PDC will restore flexibility and durability. Rejuvenation is the
softening of a pavement surface and the revitalization of the oils ability
retain the fines and aggregate. The rejuvenation process ages much
through evaporation of the coal tar rather than the rapid aging of pavement
Test studies validate the ability of
Pavement Dressing Conditioner (PDC) Asphalt Rejuvenator to
preserve a pavement, no matter how old it is, and offer a longer lasting,
black coal tar protective finish.