Rubberized Asphalt Concrete (RAC)
Rubberized asphalt concrete (RAC) is a proven road paving material that has been used in California since the 1970s. It is made by blending ground tire rubber with asphalt binder which is then mixed with conventional aggregate materials.
RAC keeps thousands of tires out of landfills with every paved mile.
RAC is:
- Cost-effective. Durable pavement requires less maintenance.
- Safe. Skid-resistant surface and prolonged color contrast make for safer driving.
- Environmentally friendly. Reduces noise pollution with noticeably lower tire noise.
Green Roads
Crumb rubber from scrap tires can be used in roadway rehabilitation.
The most common applications are:
- Rubberized hot-mix asphalt resurfacing over existing asphalt or concrete pavement, and
- Rubberized stress-absorbing membrane, also known as chip seal.
Learn more about RAC Grant Programs, which provide financial assistance to local governments to fund RAC projects.
Common RAC Questions and Answers
Are there specifications for RAC?
RAC is specified by the Greenbook, 2009 Edition, Standard Specifications for Public Works Construction and by Caltrans. RAC can be manufactured and placed satisfactorily using either specification. However, some general requirements should be included in the specification, such as:
- RAC shall include a crumb rubber modifier (CRM) consisting of at least 75 percent crumb rubber from scrap tires.
- Mixing shall be sufficient to provide a thoroughly blended, homogenous mixture of aggregates, paving grade asphalt and CRM.
- Compaction shall be accomplished by a steel-wheeled vibratory roller. Breakdown rolling shall begin before the mat cools to below 280 F.
- A minimum relative compaction of 95 percent is required.
- Gap graded aggregates should be used if resistance to reflective cracking is desired.
How do you repair patched and utility cuts?
It is generally not feasible to require RAC when repairing patches or utility cuts. On large utility projects, RAC can be specified if it is available in the area on another project. Otherwise, a conventional asphalt concrete with approximately the same gradation can be used with good success.
Does RAC reduce tire noise?
Yes. Studies have has shown that initially road noise levels are reduced significantly after repaving with RAC. Within the first few years, one study revealed that the RAC overlay still showed a noise reduction of about 5 decibels in comparison to a 2.2 decibel reduction for the conventional pavement overlay. As additional time passed, RAC still maintained noise reduction while the conventional overlay became ineffective at reducing noise.
Is special equipment required in order to construct RAC?
No. RAC is constructed using conventional pavers and rollers (steel-wheeled vibratory). An additional roller may be necessary before too much heat is lost, resulting in poor compaction and reduced life of the pavement.
Can RAC be cold milled?
Yes. This process has been done successfully.