- According to the National Asphalt Paving Association, an engineered mix of crushed rock or gravel is combined with an asphalt binder, then heated to create asphalt pavement. A refined oil product is used to make the asphalt binder. Other products, such as recycled rubber crumbs, also can be added to asphalt pavements.
- Concrete pavement also begins with a carefully designed mix of crushed rock or gravel. The rock is mixed with a cement material and water. A variety of materials, called admixtures, can be added to the concrete mix to change its engineering properties. The American Concrete Pavement Association notes that admixtures can improve the workability and setting time of concrete, entrain air to reduce the impact of freezing on pavements and adjust the strength of the concrete pavement. Reinforcing steel or wire mesh is used in some concrete pavement designs.
- Contractors place asphalt and concrete paving on a prepared subgrade and, optionally, a sub-base. A subgrade is stabilized and compacted soil. A sub-base is a layer of crushed rock placed on the prepared subgrade for roadways with heavy truck traffic or when needed to improve drainage under the pavement.
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