Asphalt is everywhere from the roads you drive on to the pavements you walk over every single day. But have you ever thought about how it is made? Read on to find out more about the asphalt manufacturing process.
Where Does Asphalt Come From?
Asphalt can still be found in natural form, in some cases. However, it is usually manufactured using petroleum products because it is more reliable and natural asphalt is in short supply.
The asphalt manufacturing process begins in oil refineries where crude oil is refined into gas and heating fuels. This is done by thermal cracking to make petrol, kerosene, and diesel. The process creates many products, including asphalt, composed of heavier, longer, and more complex hydrocarbon molecules. This base product is then used to create the asphalt that you see on roads and pavements.
Additives
The next step in the process is to add other ingredients such as rocks or sand. The asphalt manufacturing process can also include small amounts of oil additives called 'diluents,' necessary because the final product needs to be 'workable.' Before it is added to the mixture, some of these diluents are mixed with water to form an 'emulsion', which then gets blended into the asphalt material. Cutting agents may also be added to further adjust the final mix. The overall mix must be carefully blended to produce a quality end product and meet specifications, such as 'purity' and 'water resistance'.
Mixing
After the addition of rocks or sand, the process of mixing begins. This can be achieved by using different types of equipment, including dump trucks and front-end loaders. There are also specialized mixers used in some plants, which can produce batches of asphalt in under an hour. All drums use a specific amount of material to ensure the ratio is even and the batch has a guaranteed chemical composition.
Hot-Mix Asphalt (HMA)
The blended ingredients are now ready to be formed into 'Hot-Mix Asphalt'. This is the final product of asphalt manufacturing, hence why it has its name. It can either be used for paving roads straight away after production or stored in large silos. The HMA is transported by trucks to different locations where it is laid on the road.
Cold-Mix Asphalt (CMA)
Asphalt is also available as a cold mix, which is prepared offsite and transported to worksites to be laid by hand. It takes longer than HMA to set and requires higher temperatures for this process. Hot asphalt provides early skid resistance and less dust but costs more because of the equipment required for its production. Cold-mix asphalt is better for the environment and cheaper to produce but offers a lower initial skid resistance.
Environmental Considerations
The asphalt manufacturing process creates very few greenhouse gas emissions, making it less harmful to the environment than concrete. Some of the raw materials used in its production are also recycled, which also reduces environmental impact.
However, some waste products of the asphalt manufacturing process may include heavy metals and vapourised hydrocarbons. These can be released into the atmosphere during the process and may pose a threat to the environment.
Hire an Experienced Asphalt Paving Crew for Your Project
The asphalt manufacturing process is not an easy one, but it is necessary to create the material used every day on streets around your city. The team at Ajax Paving has been in the business for more than 50 years. Give our team a call today to discuss your project.