What roads are made of? How & why?


Posted by: Juliet Onyeachonam

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Most roads in Nigeria are either made of asphalt or concrete. Some others are made of chip seal. Read on to find out about the differences!

Aside from the cars we drive, another important part of our driving life is the roads being in use. Ironically, many drivers might be an expert in understanding cars but ignoring the most basic knowledge of what the roads are made of. So today, Naijauto.com brings you the answer.

Different types of roads are built for different usages or vehicle types. Ultimately, Different factors go into how roads are built and what materials are used to ensure their durability upon usage.


Concrete road under construction

As we delve into the question of what roads are made of, we’ll also get to understand why there are roads with specification regarding the types of vehicles or maximum weights of vehicles plying on them.

1. What factors are considered during road construction?

Good roads and bridges have taken centre stage in every civilization. There have never been instances of civilization in any city without the presence of modern roads for vehicular movement.

Road projects cost quite a lot from start to finish owing to the number of resources and planning that go into the design and building.

Before any road project is executed, factors such as weather conditions of the place, amount of traffic to be born by the road, and type of vehicles that will ply the road, etc. are usually taken into consideration.

Summarily, factors that are considered before any road is constructed include the followings:

1.1 Weather condition

The nature of soil a road is built on is very important to road builders. A soft soil will require thicker layers of construction materials and more compacting of the ground prior to actual construction. The reverse is the case for areas with hard soil.


Highway roads where storms happen a lot need more durable materials

Other environmental conditions such as rainfall or flood are also considered to avoid washing off of roads as a result.

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1.2 Traffic

All roads are designed with the amount of traffic that will travel through them in mind. It is true that one car will not have any effect on a well-constructed road but imagine the stress of thousands of vehicles on a road per hour!

1.4 Type of vehicle

It has been estimated that heavier trucks such as heavy-duty trucks cause as much as 10,000 times as much damage as standard passenger cars. So this should be put into consideration too.

1.5 Speed

The speedier a car is going, the lesser friction between the car tyres and the road surface. For such cases, a more abrasive road surface should be constructed. Again, faster-moving cars can cause more damage to road surfaces during braking. As a result, roads intended for up to 100 kph such as highways are constructed with thicker and denser construction materials.

2. What are roads made of?

Prior to recent times, roads were made of stones, gravel and granite. However, the modern time requires modern solutions and, therefore, asphalt and concrete have taken centre stage in most road construction projects around the world and more specifically in Nigeria.


It depends on what types of vehicles plying the road before the construction

2.1 Asphalt

Asphalt consists of a mixture of processed mineral materials such as sand, gravel, crushed rocks, slag and other constituents like fillers and binders such as bitumen. Upwards of 80% of roads in Nigeria are made of asphalt, even though concrete roads have just begun to be deployed on some roads across the country.


Asphalt road under construction

Asphalt roads are dark in colour and are cheaper to make and are also durable in the long run. Such roads have proven to handle heavy loads, even as much as some lighter categories of heavy-duty trucks.

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2.2 Concrete

Following advancements in road building technology, road builders found that other than asphalt, concrete – a mixture of sand, gravel and cement which act as a binding agent can be used to make more durable roads.

Roads made of concrete are usually lighter in colour and stronger than those made of asphalt as rods are also used in the whole setup.


Rods are used in the construction of concrete roads

The downside is that cement is quite costly and as a result, concrete roads are more expensive to build, reason it is usually deployed mostly on highways and roads that bear a lot of weight such as some Lagos roads.


Concrete roads are lighter than asphalt roads in colour but more durable

>>> Read also: Top 10 car safety facts Nigerian parents are unaware of

2.3 Chip Seal

It takes a trained eye to tell the difference between a road made of asphalt and that made of chip seal. Chip seal is the cheapest of all types of roads to build. Chip seal roads are made by steamrolling a layer of tar underneath a layer of gravel.


Chip seal road construction

Chip seal which is a combination of tar and gravel are also used to fix potholes and other road cracks and on asphalt and concrete roads.

Generally, chip seal roads are the least durable of the three and are often deployed on roads of remote areas with lesser traffic.

3. How are the roads made?

Now that we’ve answered the question of what roads are made of? You might also want to know how roads are made.

In a nutshell, one of the first things done during road construction is the removal of unwanted materials such as stones from the road to make a flat surface. Subsequently, construction materials are then added in layers with each layer being flattened and compacted by the help of a steam roller machine.


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Juliet Onyeachonam

Juliet Onyeachonam

Car maintenance

Juliet Onyeachonam is an enthusiastic car nut which is why she has turned that passion into a fantastic job by becoming a car blogger on NaijAuto.com. Juliet's blogs are a wealthy resource for information on car maintenance, driving tips and also how things pertaining to cars work.

Additionally, because of her passion for the entertainment industry, Juliet does not write only hardcore but also entertaining articles about cars.


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