How Sealcoating Prevents Damages on Asphaltic Pavements

Sealcoats provide a protective barrier on asphaltic pavements, which allows the asphalt material to oxidize slowly. The sealcoating prevents ultraviolet rays from directly reaching and heating the blacktop. When ultraviolet rays directly heat the asphalt material, they accelerate the natural or normal oxidizing process meaning that the pavements dry up and harden too fast than expected. This results to premature damages of roads and parking lots since fine hairline cracks start forming. 

"Sealcoating preserves the blacktop"

A sealcoat provides a membrane cover, which bars the ultraviolet rays from directly baking the asphalt material. When cracks are formed due to effects caused by ultraviolet rays, they allow water to penetrate and settle at the subgrade layer of roads and parking lots. Water causes more harm to the aggregate base, which is the building block for your roads. The base of roads supports the pavement layer and the loads that turns over the roads.

Water loosens the aggregate material and thus makes it start crumbling down. In addition, when water remains in the cracks, during the winter condition, it may freeze. As it freezes, the water expands and it enlarges the cracks in areas where is has collected. After the cold season, that frozen water melts down through the process of thawing and the enlarged cracks are left as empty spaces or voids.

What happens is that the material, which is on top of the void, that is, the asphalt pavement material, collapses and fills the empty space. This leads to formation of potholes in roads and parking lots. One thing with potholes and extensive deep cracks is that they are costly to repair. When sealcoats are applied in the right time, they prevent the speedy drying or oxidation of asphalt material. Sealcoats help improve the elasticity of asphalt pavements ensuring that they easily expand when heated and contract when cooled. This way, cracking is minimized.

Chemical substances like gasoline, de-icing salts, oil spillage, and transmission fluids also accelerate the oxidizing process in asphalt material. When a sealcoat is applied, it helps prevent these chemicals from coming into direct contact with the asphaltic pavement thus preventing premature damages.

In short, the oxidation process of asphalt is a complex molecular behavior, which can help understand how asphalt pavements are affected or damaged by factors like sunlight, water, snow, de-icing salts, oils, gasoline, and transmission fluids. A pavement, which is treated with use of sealcoats, can last for long thus helping prevent unnecessary expenses associated with premature damages on asphalt pavements.

When is sealcoating done?
Sealcoating is done regularly as part of the maintenance process of asphalt pavements. When a new pavement is constructed, it should be allowed to cure or dry the surface oils before a sealcoat is applied. This may take a couple of months depending on the viscosity of the asphalt and how fast it dries up. If the sealcoat is applied before the asphaltic blacktop cures properly, the coating may not fasten or bond well with the asphalt material.

After the first coating is done, other coats are applied in a period of about 2 to 5 years. This is a continuous process, which should be undertaken periodically until the end of the life of the pavements. When you notice that the color of your asphaltic pavements has changed from dark black to gray, you need to ensure that you sealcoat your drives, parking lots, and road surfaces to prevent further damages from occurring due to accelerated oxidation.

How Environmental and Man-Made Factors Cause Damages On Asphalt Pavements

Asphalt undergoes chemical changes at the molecular level and the intermolecular level also known as microstructure. Because of the complex nature of molecular interactions in asphalt, the oxidation of this material is complicated by the different molecules interrelation. There is a mixture of polar and non-polar molecules in asphalt. Polar molecules have a positive charge on one side and a negative charge on the other side while non-polar molecules have their electrons distributed in a way that there is no abundance of charges on both sides. 

"Cracks developing on asphalt surface"

In essence, there are predominantly thousands of chemicals with open chain structure in asphalt, which makes the material to have a considerable level of un-saturation in its molecular structure. It is this open chain molecular structure of asphalt, which allows it to easily interact with weather elements, chemicals, and salts. Molecules from other substances can attack and disintegrate the asphaltic material molecules leading to changes in its structural composition.

In the microstructure of asphalt, there are three-dimensional relations of polar molecules, which are referred to as asphaltenes, and these are dispersed in a fluid made up of non-polar or low-polarity molecules, which are known as maltenes. The intermolecular bonds are weaker than the bonds of the fundamental hydrocarbons in asphalt material. This means that these intermolecular bonds break up first and determine the behavioral patterns of asphalt material.

The intramolecular and intermolecular relationships in asphalt material make it behave in two major ways. First, it is elastic due to the effects caused by polar molecules interrelation. Second, it is viscous since the different parts of the polar molecules are able to move relative to one another when dispersed in the fluid non-polar molecules.

When oxidation occurs in asphalt pavement, it makes the material become dry and brittle. Exposure of asphalt to oxygen triggers a molecular process, which leads to creation of new polar bonding sites or zones. What happens is that the increased polar sites or zones in asphalt materials make the molecules to rearrange and shuffle about as they search for bonds that can create equilibrium or bring a thermodynamic stable state.

This is a self-assemblage process, which continues for the rest of the life of the asphaltic pavement material. With time, as the polar sites discover molecules to attach on, the asphalt molecules bond firmly together with the aggregate material. The result is a pavement, which is stiffer, harder, and brittle. As asphalt oxidizes and dries up, it loses its elasticity and starts to fail.

One sign that signifies the failure of asphalt due to oxidation is the change in color. Initially, asphalt has a jet-black color but over time, due to oxidation process, it turns to light black and ultimately changes to gray. The drying asphaltic material begins to crack as it loses its bonding properties. Before the oxidation process reaches an equilibrium point, it may take about 5 to 15 years depending on how the material is affected by other factors like sunlight, chemicals, and water. This substantiates the reason why the estimated lifespan of asphalt pavements is about 20 to 25 years.

When oxidation process stiffens the paving materials, its ability to support heavy loads is reduced. This causes asphalt fatigue leading to formation of cracks and premature failure of asphalt. Heat from the sun causes the asphalt material to cure and dry fast than intended. Moisture from rainfall can accelerate the damage on oxidizing asphalt since it contains a large amount of polar-constituent molecules, which in turn attract the water molecules. Sealcoating can help delay or slow the rate at which asphalt naturally oxidizes.