About 95 percent of all road infrastructure in North America is asphalt pavement. It is also used at some airports to surface the runways. It is readily available, relatively inexpensive and is considered to be a "flexible" pavement.
- South Rock Paving laying asphalt on highway 22. - The dump truck shown on the left is dumping a load of asphalt paving mix into the large hopper located in the centre of the photograph. The hopper provides storage for the paving material between dumps so that a steady supply is provided to the paving machine on the right. A sloping belt carries the paving material from the hopper and drops it into a smaller hopper at the front of the paving machine. The paving machine distributes and compacts the loose rock and asphalt making up the paving mixture. Further compaction by heavy rollers occurs behind the paving machine. (shown in picture to the right)
Photos courtesy of B. Allan
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Asphalt is the binder or glue which when mixed with aggregates (mixture of inert materials such as sand and gravel etc.) forms asphalt pavement. In some parts of the world, such as the Dead Sea (Israel/Jordan) and the Tigris River (Mesopotamia), rock asphalts occur naturally and make excellent surfacing material. Unfortunately not all naturally occurring bitumens are, by themselves, suitable paving materials.
"Artificial or manufactured asphalts represent by far the largest source of the presently consumed asphalts in all areas of asphalt technology. The largest volumes of asphalts are produced as a residue from the vacuum distillation of crude oils. The majority of paving asphalts originate this way. These asphalts are called distillation asphalts."
"It is estimated that the production of asphalt in the western world amounts to over 100,000,000 tons/ year."
Hot Mix Technologies:
"Most asphalt pavements are constructed using hot mix asphalt."
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Repaving - The surface of the road is heated and then scarified (scratched or cut) by the spring loaded tines. An oscillating, floating screed situated at the rear of the Repave machine reprofiles the surface. The surface is then immediately covered with hot rolled asphalt.
Photos courtesy of Colas
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"Research is required to develop asphalts that:
- can be mixed at lower temperatures reducing energy consumption and the production of noxious fumes....
- can be used to produce pavements that are more flexible at low temperatures and have greater resistance to deformation at high service temperatures
- can be recycled and rejuvenated when pavement performance has deteriorated below acceptable levels
- can be used with a wider range of aggregates and materials to produce satisfactory pavements"
Want to Know More?
Paving Asphalts - Power Point Presentation
International Society for Asphalt Pavements
