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.
- Cost-effective: Durable pavement requires less maintenance.
- Safe: Skid-resistant surface and prolonged color contrast makes for safer driving.
- Environmentally friendly: Reduces noise pollution with noticeably lower tire noise.
Green Roads: RAC
Crumb rubber from scrap tires can be used in various ways 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.
RAC keeps thousands of tires out of landfills with every paved mile. For more information please visit CalRecycle’s Rubberized Asphalt Concrete site.
Learn more about RAC Grant Programs, which provide financial assistance to local governments specifically to fund RAC projects.
Find out more about Technical Assistance and Training and other resources.
- 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, there are some general requirements that 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.
- 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.
- 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.
- Can RAC be cold milled?
Yes. This process has been done successfully.
- Does RAC reduce tire noise?
Yes. One study has shown that initially road noise levels were reduced significantly after repaving with RAC. Within the first few years, 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.
“The City of Thousand Oaks is quite pleased with its experience with RAC. We’ve been using RAC for over a decade and encourage the use of this product in other California cities. If we can see the benefits of RAC, so can you.”
Tom Pizza, P.E., Engineering Division Manager, City of Thousand Oaks Construction and Right of Way Management
“The Sacramento County Department of Transportation has had routine use of asphalt rubber since 1990. Since that time, we have placed over a half million tons of asphalt rubber and recycled more than 1.5 million waste tires. We now choose the product from a life-cycle savings and environmental mitigation perspective. Our investment in the use of asphalt rubber, through our maintenance overlays and capital improvements projects, has helped stem the tide of an ever increasing backlog of deteriorated pavement in our system. We feel that with asphalt rubber’s performance in rut and reflective crack resistance, coupled with the longevity, traffic noise reduction and use of a recycled product is the right choice.”
Michael Penrose, MSA, County of Sacramento