One of the most popular road construction materials is asphalt, followed by concrete, but roads can also be made from brick, gravel, and other materials. Material selection involves choosing the best option for the given conditions, considering traffic patterns, weather, cost, and noise issues. Departments of transportation typically review their options before starting new roads or resurfacing projects, to determine the best possible choice. Firms that specialize in road construction supplies typically offer an array of products.
For a high traffic road, asphalt is usually the preferred material. Known properly as asphalt concrete, it consists of a mixture of aggregate bound together with sticky asphalt and then compacted to create a roadway. Such roads require preparation to set up the road bed and design a road with the correct degree of incline; the road needs to rise in the middle to promote drainage, and it must also be banked correctly around curves, as drivers may move at high speed. Concrete is also used for some roadways.
Brick, cobblestones, and other pavers are another option for road construction materials. These tend to be used in areas where people want a specific aesthetic look and the traffic does not move quickly. Fast traffic can damage the roadway surface and may also generate a great deal of noise. Common locations for such road construction materials include historic districts and downtown gathering locations. They can also be used for driveways and low traffic roads.
Earth roads are made by applying gravel and other aggregate materials to create a drivable surface. They are suitable for low traffic, low speed areas. For areas with more traffic, a better option may be a tar and chip or bituminous surface treatment road, where aggregates are mixed with sticky binders to hold them together better. These roads will need periodic resurfacing to keep them functional, but can be a good middle point between an expensive asphalt concrete road and an inadequate earth road for rural areas.
Road construction materials for bridges, overpasses, and similar structures also include materials like steel reinforcing beams and similar supplies to create a stable structure that can withstand high weights. Structural steel, concrete, and other materials may be used to create the supports, with an asphalt roadbed to allow cars to pass. Some structures may need specialty features, like a lift bridge to allow ship traffic to pass underneath, and could require substantial design and engineering.