Oxidation: The Reason Asphalt Pavement Turns Grey

In the United States, asphalt is an essential component of our roadways, parking lots, driveways, and roofs. Americans constantly utilize asphalt pavement roadways and have been doing so since the late 1800s. Asphalt has been the main choice for pavement for so long due to its durability, smooth driving surface, and ability to protect the underlying layers from degradation. So… why does asphalt pavement turn grey anyway? In this post, we’ll discuss the root cause of why asphalt ends up turning grey over time, how asphalt deteriorates, and what to look out for on your pavement surfaces:

Before diving into the reason asphalt turns grey, we must understand oxidation. Oxidation is a naturally occurring chemical process of atoms losing their electrons. When something oxidizes, it either loses electrons or gains oxygen.

Simply put, oxidation happens when an atom, molecule, or ion comes in contact with oxygen. As you know, oxygen surrounds us everywhere, so everything on Earth oxidizes. An example of oxidation would be rusty metal. An unstable compound is created when oxygen reacts with the metal’s molecules, which leads to the creation of rust. When metal rusts, the metal loses structural integrity and eventually turns into dust.

The black color of freshly laid asphalt pavement comes from the compound chemicals in the aggregate that asphalt is made of. The main component of the overall aggregate’s makeup is called Bitumen, which is a by-product of the refining process of crude oil.

The moment that asphalt is first laid, is when the oxidation process begins. Oxidation starts slowly, but gradually becomes worse and continues indefinitely. Oxygen triggers molecular processes that create bonding sites in the asphalt. Basically, these bonding sites are clumps of asphalt joining together with the goal of reaching a thermodynamic equilibrium – which is a fancy way to say, “become stable”.

As the asphalt moves around trying to reach this stabilization, cracks form on the surface and the black pavement then becomes dried out and brittle. The oxidation paired with the harsh UV rays from the sun deteriorates and discolors the asphalt.

Now that you know how oxidation works, here are some key warning signs of asphalt oxidation and deterioration to look out for:

• Discoloration of your once-black asphalt into light grey asphalt pavement.
• Cracks formed on your asphalt parking lot, driveway, or roadway.
• Crumbling and raveling of the pavement. Raveling is when the asphalt binder deteriorates and the aggregate falls apart, leading to loose gravel, rocks, and sand on the pavement surface.

Ultimately, your best bet would be to contact an experienced professional asphalt paving, maintenance, and repair contractor who can assess your specific property conditions.

• Sealcoating your asphalt pavement at least every 2.5 years will act as a protective barrier between your asphalt and oxygen/the rapid oxidation process. Routine sealcoating will restore the black color and prevent further aging.
• Repair any cracks on your asphalt pavement with hot-applied rubberized polymer crack sealant.
• Use Infrared asphalt technology to repair more serious damages, like potholes.

The pavement professionals at Pavement Solutions have decades of experience in installing, maintaining, and repairing asphalt pavement surfaces. We know how to look out for the early signs of asphalt deterioration due to oxidation, and how to combat it. We offer a wide range of asphalt and concrete services for commercial, residential, and industrial properties. Let us show you how to get the most life out of your lot. Request your free price estimate or give us a call today at (815) 675-0696.