Rubberized asphalt concrete (RAC), also known as asphalt rubber or just rubberized asphalt, is noise reducing pavement material that consists of regular

asphalt concrete Asphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac, bitumen macadam, or rolled asphalt in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parki ...

mixed with

crumb rubber Crumb rubber is recycled rubber produced from automotive and truck scrap tires. During the recycling process, steel and tire cord (fluff) are removed, leaving tire rubber with a granular consistency. Continued processing with a granulator or c ...

made from

recycled Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...

tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...

s. Asphalt rubber is the largest single market for ground rubber in the United States, consuming an estimated , or approximately 12 million tires annually. Use of rubberized asphalt as a pavement material was pioneered by the city of

Phoenix, Arizona Phoenix ( ; nv, Hoozdo; es, Fénix or , yuf-x-wal, Banyà:nyuwá) is the List of capitals in the United States, capital and List of cities and towns in Arizona#List of cities and towns, most populous city of the U.S. state of Arizona, with 1 ...

in the 1960s because of its high durability. Since then it has garnered interest for its ability to reduce road noise. In 2003 the

Arizona Department of Transportation The Arizona Department of Transportation (ADOT, pronounced "A-Dot") is an Arizona state government agency charged with facilitating mobility within the state. In addition to managing the state's highway system, the agency is also involved with p ...

began a three-year, $34-million Quiet Pavement Pilot Program, in cooperation with the

Federal Highway Administration The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two programs, the Federal-aid Highway Program ...

to determine if sound walls can be replaced by rubberized asphalt to reduce noise alongside highways. After about one year it was determined that asphalt rubber overlays resulted in up to 12 decibels of in road noise reduction, with a typical reduction of 7 to 9 decibels. Arizona has been the leader in using rubberized asphalt, but

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

, and

South Carolina )''Animis opibusque parati'' ( for, , Latin, Prepared in mind and resources, links=no) , anthem = " Carolina";" South Carolina On My Mind" , Former = Province of South Carolina , seat = Columbia , LargestCity = Charleston , LargestMetro = ...

are also using asphalt rubber. Tests are currently underway in other parts of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

to determine the durability of rubberized asphalt in northern climates, including a 1.3 mile stretch of Interstate 405 in Bellevue and Kirkland, Washington and a handful of local roads in the city of

Colorado Springs Colorado Springs is a home rule municipality in, and the county seat of, El Paso County, Colorado, United States. It is the largest city in El Paso County, with a population of 478,961 at the 2020 United States Census, a 15.02% increase since ...

, Colorado. In 2012, the State of Georgia issued a specification for the use of rubber-modified asphalt as a replacement for polymer-modified asphalt. In Belgium, tests in the ring of Brussel and in the F1 circuit of Francorchamp (see the film by Jean-Marie Piquint ''Rubberized Asphalt'' for Esso Belgium). Two quality control requirements are necessary when using asphalt rubber: (a) crumb rubber tends to separate and settle down in the asphalt cement and therefore asphalt rubber needs to be agitated continuously to keep the rubber particles in suspension and (b) crumb rubber is prone to degradation (devulcanization and depolymerization) and thus lose its elasticity if asphalt rubber is maintained at high temperatures for more than 6–8 hours. This means asphalt rubber must be used within 8 hours after production.

Porous Elastic Road Surfaces

Porous Elastic Road Surfaces (PERS) or poroelastic road surfaces improve RAC by incorporating voids and channels, making the pavement porous and further reducing traffic noise.

References

External links

Arizona Department of Transportation Quiet Pavement Pilot ProgramAsphalt Rubber Usage Guide
from California Department of Transportation {{rubber Recycled building materials Asphalt Pavements Concrete