Dealing With Graying Asphalt Pavement

Ever notice how the dark, rich color commonly associated with freshly laid asphalt eventually gives way to a grayish shade over time? A graying parking lot or driveway can be an aesthetic turn-off for many, especially since those grayish shades are often associated with aging or worn-out parking lots. The following provides an in-depth explanation of why asphalt surfaces lose their rich black color with age as well as how to restore their youthful appearance.

It's All About Oxidation

No sooner than the final layer of asphalt is laid down, it becomes subject to a wide variety of environmental stresses. These stresses can provoke changes in the asphalt that not only impact its appearance but also its long-term durability. Oxidation is one such stressor, as the interaction between oxygen molecules, moisture and the materials that make up asphalt cause changes that eventually cause the surface to lose its dark color.

Years of constant exposure to oxygen and moisture can cause the bitumen binder that holds the asphalt together to oxidize over time. The oxidation process causes the binder to gradually break down, allowing the natural color of the aggregate to come up from the asphalt surface. This explains how a stretch of pavement turns gray as the years pass. Constant exposure to ultraviolet (UV) rays, especially in areas with year-round sunlight, can accelerate the oxidation process.

The loss of the bitumen binder also causes the asphalt to lose its flexibility as it ages. Without the flexibility provided by the binder, the now-brittle asphalt surface becomes susceptible to cracks and spalling. Without proactive maintenance, it's possible for the asphalt surface to prematurely fail as a result of long-term oxidation.   

According to the Federal Highway Administration, most of the oxidation occurs within the first 2 to 4 years of an asphalt surface's service life.

Ways to Restore Your Asphalt Surface's Appearance

Just as gray hair can be restored to a darker, richer appearance with the right treatments, a graying parking lot or driveway can also be given a new lease on life. Pavement rejuvenators can help return aging asphalt to its original color by restoring the original properties of the asphalt binder. This can also restore the asphalt's flexibility, protecting it against premature cracking.

Sealcoating is another option for restoring an asphalt parking lot or driveway to a like-new appearance. Unlike pavement rejuvenators, sealcoating involves applying a layer of emulsified asphalt onto the existing asphalt surface. The emulsified asphalt gives the surface a deep, dark color that resembles freshly-paved asphalt at first glance. For this reason alone, sealcoating is highly popular with homeowners and business owners who want to breathe new life into their parking surfaces.

Sealcoating can also protect the underlying asphalt against oxidation and UV damage as well as erosion from oils and solvents. However, frequent treatments are needed to keep up the asphalt's appearance. Most experts recommend sealcoating asphalt surfaces every 3 to 4 years, although factors such as climate and overall wear and tear can extend or shorten that timetable.

Preventative Steps to Combat Graying

The overall quality of the asphalt can play a role in its longevity. For instance, a thick, densely packed layer of asphalt is more likely to resist graying than a thinner, coarser layer. Such asphalt may also be able to resist the effects of both UV radiation exposure and the freeze/thaw cycles common in northern climates.

Using a different type of aggregate may help slow down or even prevent fading due to oxidation and ordinary wear. Aggregate made from volcanic rock, for instance, offers a deep, rich color that's slower to fade over time than other types of aggregate.

For more tips on keeping your driveway looking like new, contact a local paving company like Lakeridge Paving Company.