If you’re like most people, you encounter some form of asphalt pavement almost every day.
Freeways, parking lots, airport runways, loading docks, recreational areas, walking trails, and several other surfaces feature asphalt paving because the material is spectacularly dense, compact, strong, and able to bear considerable weight. But have you ever wondered what exactly makes up the asphalt pavement you use every day? Read on to find out.
What Is Asphalt?
First and foremost, it’s important to understand that asphalt and asphalt pavement aren’t the same thing. Asphalt (also referred to as bitumen or asphalt cement) is a black, highly viscous, seriously sticky substance that’s either semi-solid or liquid at room temperature. It can be found naturally (in which case it’s often called brea), but for paving operations, asphalt is created as a byproduct of the petroleum manufacturing process.
Asphalt pavement, on other hand, is a composite of asphalt cement (bitumen) and aggregates, which typically include various-sized rocks and sand. Combined, the asphalt and aggregates must cure to reach their full strength and density, but once cured, the pavement becomes remarkably durable.
Various grades of asphalt can be used to improve the performance, durability, and weight-bearing capacity of the installed pavement. If you’re planning an upcoming paving project, be sure to ask your contractor or supplier about your options.
How Is Asphalt Cement Made?
There are several steps in asphalt manufacturing, as well as the pavement creation process. First, crude oil (petroleum) goes through a distillation process to separate the oil into various components, one of which is bitumen. In its raw form, that bitumen is nothing more than the heavy deposits left behind during the petroleum distillation process.
After the bitumen has been extracted, it may go through a number of processes depending on its intended use, including:
- Emulsifying. During this process, asphalt is ground into extremely small globules that are only a few microns in diameter. It’s then mixed with water and an emulsifying agent to prevent separation. Emulsified asphalt is commonly used in spray-on applications or to ease the aggregate mixing process.
- Cutting back. Bitumen may also be blended with a volatile substance that allows it to retain more malleability at lower temperatures. When the asphalt pavement mixture is exposed to air or heat, the volatile substances gradually evaporate, allowing the asphalt to cure. The speed at which those substances evaporate determines the length of curing time a pavement project will require.
- Pulverizing. Sometimes, existing layers of hardened asphalt are crushed into powder and forced through several sieves to create uniform-size granules. Typically, the powdered asphalt is then blended with aggregates and oil for pavement rehabilitation. Pulverized asphalt is extremely durable and since it’s derived from existing asphalt, it’s more eco-friendly too.
How Is Asphalt Pavement Made?
There are two types of asphalt pavement: hot mix and cold mix. Hot-mix pavement is manufactured by heating the bitumen and aggregate to high temperatures before the amalgamation process to eliminate all moisture from the mix. Heating the mixture also allows it to reach the appropriate fluidity for proper mixing and pavement installation. Typically, hot-mix pavement is installed anywhere that sees considerable traffic, such as highways and major arterial roadways.
Cold-mix pavement, on the other hand, is the most basic form of asphalt pavement and is far less durable than its hot-mix counterpart. As the name implies, this type of pavement doesn’t require any heating during the amalgamation process and is typically used when outdoor temperatures are too low for hot-mix.
Given its lack of strength, cold-mix asphalt is really only suitable as a temporary patching agent or for small-scale asphalt repairs. Ideally, it should be replaced with hot-mix asphalt when outdoor temperatures allow.
Need Asphalt Paving, Maintenance, or Repair in the Twin Cities? Contact Bit Roads
Whether you’re in the market for asphalt paving, asphalt repair, paving maintenance, patching, pothole repair, or drainage solutions, our team at Bituminous Roadways can help. For over 75 years, we’ve proudly served commercial and industrial operations with the highest quality asphalt paving services in the Twin Cities metro. We operate our own asphalt production plants right here in the metro area and since our founding, top-notch service and quality workmanship have always been our priorities.
To learn more about our services or get an estimate for your upcoming project, feel free to give us a call today at 651-686-7001 or request a consultation and estimate online. We look forward to hearing from you!