How is Asphalt Made
Even though you see it just about everywhere, most people don’t think a whole lot about asphalt. Everyone knows that roads, parking lots, and sidewalks are made from asphalt, but what else is? Airport runways, tennis courts, bike paths, coating for pipes, roof coating, and even the undercarriages of vehicles use asphalt. Some lesser-known uses for asphalt include capsules for radioactive waste, sealant on batteries, and waterproof covering for fabrics. Its most-common use, however, is for road surfaces, as about 85% of asphalt is used in road building.
The word itself comes from the Greek ásphaltos, which roughly means to stop something from falling down. The oldest known use of asphalt is in the 5th century BC, lining a basket for holding crops. It has been used to line baths and even to caulk ships, and ancient North Americans used it to attach heads to arrows and spears.
But what is asphalt and how exactly is this surprisingly present substance made?
What is asphalt?
Asphalt, known also as bitumen, is a sticky, black, semi-solid form of petroleum (oil). It can be found naturally in oil deposits. Places like the La Brea Tar Pits in Los Angeles, the Dead Sea in Israel, and other large pits can contain natural asphalt.
Most asphalt today, though, is refined from crude oil.
Asphalt is used as the glue to bind together small, rocky pieces of what is usually gravel or small stones. This is usually known as pavement.
Asphalt is commonly used in roads, but it is also a waterproofing and sealing agent.
Most asphalt is made according to what it’s required to do—that is, the process is different whether the final product is road pavement, airport tarmac, or pipe coating. There are some similarities in how all asphalt is made, though.
Step one of making asphalt is distilling crude oil. This means that the crude oil is separated into different parts, usually with chemicals or heat. The separated parts become various things; gasoline, kerosene, diesel, and other oil products. The heavy compounds left over from the distilling process make “topped” (distilled) crude oil for heating gas and other products like asphalt.
Asphalt may be blended with other agents to create asphalt for different uses. The blending process, called “cutting,” varies according to the cutting agent. Whatever cutting agent determines how light the asphalt is, how easy it is to change its form it is, it’s melting temperature, and how quickly it sets (hardens).
Asphalt can also be emulsified, which means that small droplets of one liquid become dispersed throughout another liquid (that’s a very simple definition, mind you—if you are curious about emulsifying in depth, look here). Asphalt may be emulsified by water, clay, soap, vegetable oils, and more. Some common emulsions are vinaigrette and homogenized milk. The emulsifying process lets asphalt be sent through tubes, or sprayed.
Crushing and Filtering
Hardened asphalt is sometimes pulverized and then filtered until the tiny granules are the same size. When mixed with oil and aggregate (the small pieces of rock and gravel), asphalt can be used for pavement construction.
If the asphalt will be used as a coating, it is often treated with air. Heated asphalt is pumped with air until air bubbles form in it. This process makes asphalt that can stay in a liquid state even at low temperatures.
In the United States, asphalt and pavement are often used interchangeably. However, asphalt actually only makes up about 4-5% of pavement weight, and is by-far, it is the highest-cost part of road paving materials. Asphalt has more than tripled in price since 2002, now costing more than 610 dollars per ton. For more information on asphalt’s usage in highways and costs, check here.
There are a few main types of asphalt used in paving, and they go by the simple names: hot mix, warm mix, and cold mix.
Hot Mix Asphalt
Hot mix asphalt is most likely what you see all around you. Odds are high that this is the asphalt used in paving projects on the streets and highways.
Hot mix asphalt is made by heating asphalt to between 300 and 350 degrees Fahrenheit. It is then poured at that temperature. Hot mix asphalt repels water and is strongly weather resistant, hence its popularity. Finally, it also sets quickly, so it can only be poured on days that are over 40 degrees.
Warm Mix Asphalt
Using fewer fossil fuels and a lower temperature (200-250 degrees) than hot mix, warm mix is used in less construction, but is can be used in more situations as well. It cools more slowly, so can be poured in colder climates, and it is also easier to ship. Warm mix asphalt is generally cheaper than hot mix asphalt.
Cold Mix Asphalt
Cold mix asphalt is the cheapest of the three, but has a much narrower range of use. It is usually used for repairing the other two types of mixes. It fills cracks and potholes, and is more of a stopgap measure than a permanent solution. Cold mix does not last as long as the other two mixes.
Pavement is actually made up of about 95% aggregates. So one of the final steps in making asphalt is to mix in sand, gravel, and stone. For detailed information on how asphalt is used, what it’s future could be, and how it’s made, check out this article, too.
Getting the Highest Quality Asphalt Services
The educated buyer will want a paving contractor that not only provides a range of paving services, but also ensures quality and legal compliance. Seal coating, asphalt paving, asphalt repairs, crack sealing, and more are all some of the top-quality services offered by Reliable Paving, based out of Arlington, Texas.
Our high-quality equipment and well-trained staff can guarantee you the best asphalt and paving-related services for your dollar. To get the best paving you can, contact us at Reliable Paving today and we will get right in touch.