By Vaageesha Das
What are roads made of?
Some roads are bumpy because they are filled with potholes.
Other roads are as smooth as can be, while still others are somewhere in the middle of this spectrum.
A blind man named John Metcalf (1717-1810) built 180 miles of roads during his career. His roads consisted of three layers: large stones, road material that was dug out, and a last layer of gravel.
In the late 1800s, roads were made only of stone, gravel and sand. Water was used to bind these materials together.
Our modern roads have evolved upon the designs of two Scottish engineers, Thomas Telford and John Loudon McAdam. Telford analyzed road traffic, gradient stones, alignment of road and stone thickness. He also added the method of using broken rocks to build roads.
McAdams designed roads so that they would have patterns of big rocks that were laid symmetrically, and the holes between those rocks were filled with smaller stones. This design is called the “macadam roads.” This was the greatest advancement in the construction of roads.
In America, about 96 percent of roads are surfaced with asphalt. This is an equivalent of two million miles.
Man-made asphalt is made of hydrogen and carbon compounds with a little bit of sulfur, oxygen and nitrogen. Asphalt was first used for roads in 1824 in Paris.
In some parts of the country, asphalt is used while in others, concrete is used. Concrete wears out faster than asphalt. In terms of weather, asphalt wears out faster in warm areas than it does in cooler areas. Asphalt also used to be cheaper but now the price has gone up. There are many variables as to why asphalt is used in some places and concrete in others, like cost, usage, amount of time to wear, etc.
You might also be wondering how potholes are made. When the weather gets colder, water seeps into the roads and gathers on the frozen soil. Once the ice melts, there is a void underneath the road. The vehicles drive on top of that area, which makes the surface collapse into the void and, as a result, you get a pothole.
In hot weather, the heat coming from the sun dries out the “glue” in road materials, which causes water to seep in. The material and the road bed are softened by the water. The heat from the sun continues to damage the asphalt (or the concrete) and it is unable to hold the weight of the vehicles. The driving vehicles keep driving over it and the pothole slowly develops.
Vaageesha Das is going into ninth grade at Morgantown High School. Today’s information comes from: Bellis, Mary. “Follow the Evolution of the Road from Path to Pavement.”
