Rubberized Asphalt Concrete (RAC) and Rubberized Chip Seal (RCS)

 

 

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.

Rubberized Chip Seal (RCS) includes the placement of a rubberized asphalt binder and application of conventional aggregate material.

RAC and RCS keep thousands of tires out of landfills with every paved mile.

Rubberized asphalt concrete (RAC) and Rubberized Chip Seal (RCS) offer the following benefits:

Environmentally Friendly 

RAC and RCS are environmentally friendly products before they are placed on the streets, by diverting scrap tires from landfills and reducing waste. Waste tire rubber is recycled and used in RAC and RCS and reduces the dependence on landfills. RAC and RCS materials have also proven to result in fewer greenhouse gas emissions over their lifetime during construction as well as due to better performance compared to conventional hot mix asphalt. Studies have also noted a significant reduction in noise levels (2-3 dB which represents up to a 50% reduction in noise) from using rubberized asphalt on higher speed (> 35 mph) locations.

Improve Performance

RAC and RCS materials have shown a higher resistance to cracking, a better performance against heavy traffic in the form of reduced fatigue cracks as well as rutting. Studies in California have shown RAC is effective in resisting the propagation of reflective cracking from the underlying pavement structure. The improved performance of RAC and RCS materials extends pavement life.

Cost Effective

The improved performance of RAC and RCS materials results in reduced need for future treatments over the life cycle of the pavement structures. Reduced maintenance also means fewer disruptions to traffic and increasing the effectiveness of the public taxpayer money.

Safe

Skid-resistant surface and prolonged color contrast make for safer driving.

Grant Funds Available for Rubberized Pavement Projects

Find out how your agency may qualify for a CalRecycle grant. The Rubberized Pavement (TRP) Grant Program provides financial assistance to local governments to fund RAC/RCS projects.

Rubberized Pavement Grants

Green Roads

Crumb rubber from scrap tires can be used in roadway rehabilitation.
The most common applications are:

  • Rubberized hot-mix asphalt (or RAC) resurfacing over existing asphalt or concrete pavement
  • RCS, also known as chip seal, over existing asphalt or concrete pavement
  • Rubberized stress-absorbing membrane chip seal on existing pavement as an interlayer under an overlay

Learn more about these pavement applications by accessing the following resources:

CalRecycle RAC guide thumbnail  Greenbook thumbnailCaltrans standards specification thumbnail

*Not available at this time, but will be available at a later date.

Technical Assistance. CalRecycle provides engineering and technical assistance to local jurisdictions for education, design, and construction oversight on RAC/RCS projects in California. For more information, see the Technical Assistant and Training website or contact RAC@calrecycle.ca.gov.

Common RAC and RCS Questions and Answers

Are there specifications for RAC?

RAC is specified by the Greenbook, 2024 Edition, Standard Specifications for Public Works Construction, and by the Caltrans Standards Specifications. 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 15% crumb rubber from scrap tires by weight in the liquid asphalt binder.
  • 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, and all compaction complete before the mat cools to below 250 F.
  • A minimum relative compaction of 95% is required.
  • Gap graded aggregates should be used to accommodate the crumb rubber particles.

For more information, see the Specification Templates listed on this webpage.

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 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.

The amount of noise reduction from RAC is a function of posted speed limit and truck volume. For roads with posted speed limits below 35 miles per hour and/or high truck volumes (greater than 7% of average daily traffic), the benefit of noise reduction is reduced.

Is special equipment required in order to construct RAC or RCS?

Yes. For RAC, mobile equipment must be brought to the asphalt plant to proportion and blend the crumb rubber and liquid asphalt. 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.

For RCS, a specialized spray distributor truck is used where the crumb rubber is blended with asphalt oil and then sprayed onto the pavement. The distributor truck must be equipped with a hood vacuum for smoke, and the chip spreader must have a heat-resistant belt due to the hot chips that are used.

Can RAC be cold milled?

Yes. This process has been done successfully.

Reports and Resources

CalRecycle Reports

Other Resources

Related Links 

For more information, contact RAC@calrecycle.ca.gov.