Combatting Asphalt Pavement Oxidation

Posted on: 12 January 2017

Just as human hair eventually starts graying, your freshly-laid parking lot will eventually lose its rich, dark color over time. What will be left behind is a grayish surface that can make your parking lot and its surroundings appear much older. The culprit behind this inevitable phenomenon is oxidation of the bitumen binder used to keep the asphalt aggregate together. The following explains why this process happens and what you can do to keep it from happening.

Why Oxidation Happens

For asphalt parking lots, the oxidation process begins no sooner than the last bit of pavement is laid down. A combination of oxygen, moisture, ultraviolet radiation and overall wear and tear from vehicular traffic causes the bitumen binder to lose cohesiveness as time passes. The binder wears away eventually, slowly stripping the pavement of its original dark color until it begins to take on the color of the underlying aggregate, which is usually gray in appearance. In some areas, the asphalt may begin to take on a reddish tint due to the dirt or clay content of the aggregate sourced from the local area.

The loss of bitumen binder can also accelerate the wear and tear of the asphalt surface. The bitumen supplies the asphalt with much of its flexibility and without it, the asphalt becomes more vulnerable to cracking, breaking and chipping at joints and crack edges.

Repairing Oxidized Pavement

If you're dealing with a parking lot that has already lost its dark color, then you may be able to revitalize it using one of two methods. The first involves the use of pavement rejuvenators to return the pavement to its original color. Pavement rejuvenators accomplish this by restoring the pavement's original balance of asphaltenes and maltenes - two molecular substances commonly found in asphalt. This also brings back the original flexibility of the asphalt surface, which helps prevent additional cracks and other surface imperfections from forming. The only downside to using pavement rejuvenators is that it reduces the pavement's skid resistance.

The second method involves laying a coat of emulsified asphalt over the existing surface. This technique, known as sealcoating, allows the asphalt surface to appear as it once did when it was new. In addition, it can also protect the underlying asphalt against ongoing damage due to UV exposure and chemical erosion. Sealcoating requires regular treatments every few years to remain effective, plus the coats usually aren't thick enough to cover obvious flaws in the pavement surface. As a result, you'll need to have potholes and other imperfections patched prior to sealcoating.

Preventing Oxidation

Prevention is often the best policy when dealing with pavement oxidation. The preventive process should start at the planning stages of your parking lot paving project. Choosing the type of asphalt to be used for your parking lot can be an effective tactic against oxidation. Thick layers of dense-graded aggregate are more likely to withstand the oxidation process than thinner layers of asphalt made from coarse aggregate.

Using volcanic rock and ash as a substitute for conventional aggregate may also help when it comes to preventing oxidation of the pavement surface. The properties of volcanic rock and ash lends itself well towards resisting fatigue when subjected to UV radiation and other stressors, plus it also features a naturally rich, dark color that's not as prone to fade as pavement made from ordinary aggregate.

Preventive sealcoating of fairly new asphalt parking surfaces may also be a viable preventive step against oxidation. Sealcoating can not only protect the underlying asphalt from further deterioration and help it maintain its rich color, but it may also extend the working life of the asphalt surface itself.

Discuss your options with a professional asphalt company in your area for more about this topic