Rubberized Pavement Among Markets Featured At California Tire Conference

Expanding the use of recycled tire rubber in more markets was a key theme for tire recyclers, state regulators and industry stakeholders attending the California Tire Conference held in Sacramento in August.

The well-attended conference sponsored by the California Department of Resources Recycling and Recovery (CalRecycle) provided updates on the state of tire recycling in California, as well as the latest scrap tire management figures and trends for the U.S. and Europe. Presenters also talked about market and product development initiatives emerging in California and nationwide spurred by manufacturer and consumer interest in sustainable material recycling.

CM Shredders

Recycling tire rubber in rubberized pavement applications has been a diversion and material recycling strategy supported by the former CIWMB (California Integrated Waste Management Board) and CalRecycle since the very beginning of the state’s tire program, Nate Gauff, Waste Management Engineer at CalRecycle said.

The use of rubberized pavement by the California Department of Transportation (Caltrans) and local agencies currently diverts about five million waste tires per year from landfill disposal.

Over the past twenty-five years of California’s tire program use of rubberized pavement has diverted an estimated 80+ million waste tires.

One of the ways Caltrans and CalRecycle and local government road departments have been unable to expand the use of tire rubber in pavement is through the use of research contracts to fill in gaps in the knowledge base, determine feasibility of technology, and investigate new processes and materials.

For the research contracts, CalRecycle partners with entities that have a proven expertise with rubberized pavement projects and / or research, Gauff said. These partnerships have led to research contracts for a Terminal Blend Chip Seal Demonstration Project and another demonstration project studying the use of Reclaimed Asphalt Pavement (RAP) in Chip Seals.

Research contract partners are also conducting a LifeCycle Cost Analysis (LOCA) for rubberized asphalt concrete (RAC) materials and carrying out performance evaluations for warm mix asphalt, Gauff said. Performance models for RAC RAP in Hot Mix and RAC Chip Seal are in development, he said.

PG+X, a multi-year CalTrans research effort now underway seeks to incorporate 5-10 percent crumb rubber in all asphalt binder. Under the current contract researchers have performed laboratory evaluation of binder impacts for three different production processes. PG+X could potentially double the use of crumb rubber in asphalt, he said.

The goal for researchers working under the research contract for PG-AR & Rubber Quantification is to develop a new specification process for asphalt-rubber binders that correlates to the existing Performance Grading (PG) system for asphalt binders.

CalRecyle is funding the validation testing of the PG-AR methodology, Gauff said, Once finalized it will be a nationwide specification, he said.

The first study looking at the use of reclaimed asphalt pavement in the context of binder replacement was carried out in a two-year research contract from 2014 through 2016.

The current study will look at the use of RAP in the context of aggregate replacement, Gauff said. It will also perform evaluations for both gap graded and open graded rubberized hot mix asphalt.

Gauff said Cal Recycle continues to support rubberized pavement in the state through the reearch contracts and other initiatives including technical assistance and training, product and vendor information dissemination and Green Roads fact sheets. The use of rubberized pavement represents the largest recycling use of California’s waste tire rubber, Gauff said. Rubberized pavement has also demonstrated superior performance over conventional asphalt concrete and is durable, long lasting and requires less maintenance. It has also been shown to be a cost beneficial resurfacing option over conventional asphalt concrete.

More roads paved with ruberized asphalt

In addition to continuing research for, Caltrans continues to pave more California roads and highways with rubberized asphalt pavement mixes. A recent $3.3 million dollar project completed on State Route 99 near Stockton in San Joaquin County resurfaced over four miles of SR 99 in Stockton with rubberized asphalt concrete.

Also, a $2.6 million dollar project now under construction will resurface almost four miles of U.S. Highway 101 in the Myer Flat area in Humboldt County with rubberized asphalt.

© Scrap Tire News, October 2018