Freshly laid asphalt has a deep, rich dark color, but over time that color can fade into a grayish hue. This can make your asphalt surfaces look old and tired, sometimes even before their time. If you're dealing with a graying driveway or parking lot, you'll want to find out what causes pavement to turn gray and how to keep it from graying.
What Causes Pavement to Turn Gray?
The clock starts ticking for your asphalt pavement the moment it's laid down. From the start, oxygen molecules, moisture, and ultraviolet (UV) rays join forces to slowly but surely break down the asphalt binder. This combined assault, along with the stresses of regular foot and vehicle traffic, can wear down the asphalt binder over time. As the binder disappears, the natural gray color of the asphalt begins to come through the pavement.
Losing the binder due to the effects of oxidation can spell long-term trouble for a paved surface. Without the binder, the aggregate begins to unravel, exposing the individual stones imbedded within the paved surface. Hairline cracks begin to form in the pavement, only to grow bigger as water and vegetation erode and expand the cracks. The end result is pavement that not only looks tired, but is also left with a short life expectancy.
Rejuvenators Can Add New Life to Old Pavement
One way to breathe new life into oxidized pavement is by restoring the ratio of maltenes to asphaltenes in the pavement. Maltenes are usually lost through exposure to UV rays and the oxidation process. Pavement rejuvenators work by adding maltenes back into the pavement, bringing the ratio of maltenes to asphaltenes back into balance. This strengthens the binder while making the pavement more flexible. In addition to restoring the surface's original dark color, rejuvenators also help prevent cracks and other damage from forming.
The only downside to using pavement rejuvenators is that they can reduce the skid resistance of asphalt pavement. For this reason, it's best to use rejuvenators on parking lots and other paved surfaces that normally see low speeds and low volumes of traffic.
Sealcoating Can Also Restore Asphalt Surfaces
Another way of bringing graying asphalt pavement back to black involves the sealcoating process. Sealcoating adds a layer of emulsified asphalt on top of the asphalt surface, essentially covering over the graying asphalt with a more attractive black finish. A sealcoated surface is usually indistinguishable from freshly paved asphalt, which makes it a cost-effective alternative to destroying and repaving asphalt surfaces.
Regular sealcoating treatments are usually required to maintain the asphalt pavement's rich, dark color. The sealcoating process won't replace lost maltenes, nor will it restore the pavement's lost flexibility. In addition, sealcoating should be avoided on pavement that's showing significant cracks until those cracks have been successfully repaired, since said cracks can easily be seen through the sealcoated surface.
Other Preventive Measures Can Help Preserve Your Pavement
When it comes to graying asphalt pavement, prevention is the best policy. These preventive policies include using an alternative type of aggregate in the paving process. The type of aggregate used often influences the ultimate color of the asphalt surface, which explains why some parts of the U.S. have paved roads with a slight reddish tint. An aggregate with a rich, black color, such as volcanic rock, can be used to create a paved surface that resists fading over time.
Premature graying can also be thwarted by creating thicker, denser layers of asphalt. The thick asphalt is more likely to resist oxidation and subsequent fading. In addition, it may also be more resistant to cracks caused by moisture and vegetation.
Reach out to a local paving contractor for more information.