Did you like to play with toy cars when you were a little kid? Maybe you still like to play with toy cars today. We do!
Have you ever taken your toy cars outside to play? If you have a beach or a patch of dirt nearby, it can be so much fun to build your own roads for your cars to drive on. All you need is a rock or a toy shovel to clear a path for your cars to speed down like a highway.
It might be easy to make pretend roads for toy cars, but real roads for real vehicles are a lot more difficult to build. Although rocks and real shovels are often involved, it takes quite a few people and a lot of special equipment to build a real road.
The first step in building a road is planning. Many people, including engineers and construction experts, must be involved in figuring out what type of road should be made — and what it should be made from — depending upon the amount and type of traffic it will likely see.
Even simple roads can take months of planning before construction can begin. Complex roads that involve different structural elements, such as bridges or overpasses, can take years to plan. Other factors that planners must consider include environmental impact of the road, cost, availability of materials, and safety.
Toward the end of the planning phase, surveyors and construction experts will develop solid plans for the road to be built. If part of the land to be used for the road is owned by private parties, lawyers and government officials will need to negotiate the purchase of pieces of property to be used for the road.
Public meetings will also often be held, so that any citizens with concerns about the road construction project can voice their opinions. The local, state, or federal governmental entities building the road will also solicit construction bids from a variety of contractors to make sure that the road can be built as economically as possible.
The first part of construction is one of the most important: earthwork. Huge earth-moving machines must be used to create a solid foundation for the road to be built. Without a solid foundation, any road that is built will fail long before its expected lifespan.
Bulldozers and graders move around dirt delivered by dump trucks to create a level surface that will support a road for many years to come. Gravel is added in layers and machines roll over the surface to compact and flatten it further. Drains and storm sewers are also installed at this early stage, so that rain will drain away from the road surface and make it easier for vehicles to travel in storms.
Once the foundation is finished and has been inspected, it's time to pave the way! The most common materials used for paving roads are asphalt and concrete. Factors such as cost and type and amount of traffic will determine which material will be used.
Asphalt uses an oil-based substance called bitumen to make sand and crushed rock stick together like glue. After the asphalt is heated to about 300° F, it is transported to the construction site, where construction crews spread and compact it onto the foundation already in place.
Concrete also uses sand and crushed rock, but it's held together with cement. Workers must pour liquid concrete into special steel molds called forms. As it dries, a special finishing machine vibrates it to make it settle evenly and then trims it to the correct height.
To prevent cracks, workers make cuts — called joints — between concrete slabs. These joints allow the concrete slabs to expand and contract with changes in temperature without breaking.