Everyone has encountered asphalt at some point in their life. It covers the roofs of our buildings, it smooths the parking lot of the grocery store, and it paves our roads. It’s everywhere. Asphalt is a versatile building material that lasts a long time and can take a ton of abuse. While we all know what it is, most of us don’t know how asphalt is made. It’s actually an eco-friendly material that recycles old materials. Construction companies that use asphalt to pave roads use recycled stone in the mix. When they remove the old road or parking lot, they crush the pavement to use again. Many compare asphalt to concrete, and there is debate over which is better. While concrete will last longer, there are benefits that asphalt has over concrete, particularly in parking lots.
What Is Asphalt?
Asphalt is not the whole, meaning it’s not the rocks and the black tar. Asphalt is the material that binds the crushed stone and gravel together to create a strong, hard surface. The crushed stone is called aggregate. Asphalt is a bitumen-class hydrocarbon mixture that has a dark-brown to black color. Bitumen is the geological term for naturally occurring deposits of petroleum in a solid or semi-solid state. While natural asphalts were popular until the early 20th century, most asphalt today is refined from petroleum-based products. The “artificial” asphalt has the same characteristics as natural asphalt but with the added benefit of uniformity and fewer impurities.
How Is Asphalt Made?
Modern asphalt comes from crude oil and not naturally occurring minerals. Oil refineries take the natural crude and refine it down into dozens of other products. First, they heat crude oil rapidly for distillation. Once heated, the oil moves into a distillation chamber where a series of cooling and condensing mechanisms remove the more volatile components. The crude is then separated to produce different products such as asphalt, gasoline, kerosene, and diesel fuel. The asphalt is then blended in a process called cutting back. It mixes with a substance that makes the asphalt more malleable at lower temperatures than chaste asphalt. When exposed to heat or cool air, the mixed substances evaporate, leaving behind the solid asphalt.