Whether you’re a driver or a passenger, any motor vehicle you ride these days is likely driving on asphalt roads. Asphalt is a common material used for paving roads worldwide and is often used for private roads and driveways, too. But what makes asphalt so popular?
Asphalt consists of an aggregate, a binder, and a filler material. Together, they’re layered onto a road to create a surface that offers many benefits. Asphalt roads are more affordable and quicker to build while also being easy to repair and maintain. They also reduce noise and help vehicles maintain traction, keeping them safe on the road.
This guide will walk you through everything you need to know about asphalt roads. You’ll learn why they’re a popular choice worldwide by discovering how they’re made and what benefits they offer.
Let’s get started.
What Is Asphalt Made Of?
The first step to answering the question “Why do we use asphalt for roads?” is to understand what asphalt is made of.
Once you know what’s in asphalt and how it’s used, you’ll have a much easier time understanding why it’s arguably the most common type of road anywhere in the world.
Asphalt is a paving material that consists of three parts:
- The aggregate: This part forms the bulk of asphalt’s overall structure. It consists of processed mineral materials like sand, gravel, crushed rock, and more.
- The binder: Asphalt also consists of an adhesive binder. In simple terms, this material glues the aggregate material together and helps them keep a consistent shape. The most common binder used for asphalt is bitumen, a sticky black material that typically comes as a byproduct of petroleum distillation.
- The filler: Lastly, asphalt also consists of a filler material that fills any voids while keeping the mixture cohesive.
After producing asphalt with the materials listed above, it’s then placed on top of a road base in several layers. Those layers are:
- The surface layer: The top layer of the road interacts with the vehicles driving on top of it. The layer is durable enough to sustain the weight of those vehicles while also reducing noise and helping them maintain traction.
- The binder layer: The binder layer sits between the surface and the base. It provides both stability and durability by sustaining plenty of the stress from the weight above. In doing so, this layer helps to prevent ruts from forming.
- The base layer: The base layer sits at the bottom, which is quite stiff compared to the others. It helps distribute the weight from the vehicles above and prevents the ground from experiencing too much stress.
Overall, the combination of its materials and the way asphalt is layered bring out its best qualities. Together, that’s what makes asphalt a popular choice for paving roads.
When Was The First Asphalt Road Laid?
Asphalt is not a new technology in road paving. Instead, it’s been around in the United States since the late 1800s and has been used ever since.
In modern history, asphalt roads can be found as far back as the late 1700s. Englishman John Metcalf is said to have built the first asphalt roads in Yorkshire. Later in the early 1800s, Thomas Telford did the same in Scotland.
However, in the United States, Professor Edward J. de Smedt of Columbia University was credited for first using asphalt in 1870. As a result, thanks to its layered construction, the material was first known as ‘sheet asphalt pavement’. Alternatively, the material was also known as French asphalt pavement.
Later on the 29th of July of the same year, asphalt was first used on William Street in Newark, New Jersey.
Altogether, these events marked the beginning of asphalt’s use in modern roadworks, which continues until this day.
Why Do We Pave Roads With Asphalt?
There are several reasons why governments worldwide have chosen to build their roads using asphalt.
So, why do we use asphalt for roads? Here are the reasons:
- Affordability: First and foremost, asphalt is a very affordable alternative to other road-building materials like concrete. Budgeting to build asphalt roads is much easier for local governments.
- Time-saving: Besides being more affordable, layering asphalt roads also takes a lot less time to complete. That means roads can be built faster and used sooner by the people who need them the most.
- Easy maintenance and repairs: Damage and wear are typical for any type of road. Asphalt roads have the advantage of being easy to repair in patches and also maintained throughout their useful lifespan.
- Noise reduction: As you saw from the previous sections above, asphalt also has noise reduction qualities. With many cars passing over, the noise pollution is significantly lower than on roads made from other materials.
- Heat absorption: Asphalt is known for absorbing a lot of heat. Hot pavement isn’t pleasant on bare feet, but it’s excellent for cars. A hot asphalt road melts ice faster and evaporates excess moisture, preventing slippery roads.
- Recyclable: Lastly, you can melt any unwanted asphalt down and recycle it by building new roads elsewhere.
What Are Drawbacks Of Using Asphalt For Roads?
Everything comes with its fair share of cons or drawbacks, including asphalt roads.
Some of those drawbacks that we’ve all likely seen with our own eyes include:
- Limited lifespan: Asphalt roads typically last about a decade, unlike concrete roads that last longer. So, asphalt roads require repairs relatively more often than other road materials.
- Rain and cold weather damage: Earlier, you saw that hot asphalt roads could evaporate water quickly. That’s true, except for situations like heavy rains and cold weather. Asphalt roads in wet or cold climates will suffer more damage to their top layer.
- Oil damage: Oil spills can also undermine the binder material in asphalt roads, causing significant damage.
But why do we use asphalt for roads despite these drawbacks? Simply put, the benefits significantly outweigh the disadvantages. Of course, asphalt isn’t perfect, but it still comes out on top as the preferred choice for paving roads despite its shortcomings.
Asphalt roads are likely the most common type globally, as many local governments prioritize affordability over a long lifespan. Still, some governments go the other way, choosing to invest in concrete roads that last longer than asphalt.
However, there’s little chance that asphalt will stop being used to build roads anytime soon. Despite its limitations, asphalt maintains its preferred status by fulfilling the budgetary and quality needs of many governments worldwide.