Recycled Materials Demonstration Projects

FHWA Priority Technology Project (PTP)

To help implement earlier research, TxDOT was awarded a Federal Highway Administration Priority Technology Program (PTP) grant to monitor and report results from 12 field tests of recycled materials used in road construction.

The main objectives of this project are to (1) clearly document engineering and economic benefits of recycled materials, and (2) disseminate knowledge of recycled materials beyond those directly involved in each field test.

The 12 field tests are:

Research: Texas Tech University engineers are monitoring the projects, conducting visual observations, interviewing project personnel, and testing the performance of the installed projects. Case studies and a final research report will be prepared.

Communication: Brief demonstrations are held for TxDOT employees, local and municipal road construction staff, contractors, other local road building partners, and representatives from trade and local media at the project site. Each demonstration includes an information showcase, which is a brief (two hours or less) overview of the project. The showcases typically present:

• Background research
• Project summary
• Contractor's perspective
• Information from the recycled material supplier.

This format allows attendees to understand the perspectives of TxDOT, of the contractor, and of the material supplier and how they fit together. If appropriate, a visit to the construction site is also included so attendees can see firsthand how materials perform.

Showcase participants receive information compiled by Texas A&M's Texas Transportation Institute, including:

• Background information on the use of recycled materials in road construction
• Research summaries on the material
• Summary of information presented in the demonstration.

Other communication tools help spread the word to TxDOT employees, industry personnel, and road building partners. A communication vehicle that's proven instrumental in generating worldwide interest is a media release to road construction and recycling trade publications. Many people who were unable to attend demonstrations have requested additional information. In addition, TxDOT employees receive supplemental information through newsletters, presentations, and display booths at various TxDOT conferences.

Printer Toner in Hot Mix Asphalt Pavement

A significant amount of printer toner is wasted every year. A conservative estimate is 25,000 tons per year. The toner industry pays more than $70 per ton for landfill disposal. Toner is approximately 85% styrene polymer and 5% to 15% carbon.

TxDOT's Waco District, in conjunction with the Center for Transportation Research, conducted research concluding that waste toner can be successfully recycled into asphalt. Waste toner improves the strength of asphalt, acting as a beneficial modifier. Specifications, methodology, and procedures for practical implementation were developed.

In July and August of 1997, Loop 396 (Valley Mills Drive) in Waco from Bosque Boulevard to Waco Drive was milled and overlayed with a 50mm Superpave 19mm mix. The Superpave mix (PG 64-22 ) was mixed with approximately 7.5% toner. The roadway consisted of six travel lanes of 3.6m width, with a 4.6m continuous left turn lane. A control section was paved using asphalt mix without toner for comparison. The price of asphalt mix with toner was $43.95 per megagram. The price of asphalt mix without toner was $41.23 per megagram.

The asphalt binder was mixed with toner on-site with a mobile shear blender. The blender was connected to the asphalt plant. There were 6,500 megagrams of Superpave mix with toner. This was done by Advanced Asphalt Technologies Corporation. The toner was donated by Ricoh Corporation and Sharp Corporation.

Currently the performance of the asphaltic pavement is excellent. There is no significant difference between the asphalt pavement with the toner and the control pavement. Both pavements are very new. In time, TxDOT engineers predict the toner-modified pavement will provide increased resistance to rutting. Also, this pavement is predicted to have a longer life than the control section.

TxDOT is applying for a United States patent on the process used for incorporating toner into hot mix asphalt.

Crumb Rubber Hot Mix in Odessa

The Odessa District is experiencing good success with the Asphalt-Rubber hot mix overlay and Asphalt-Rubber Open Graded Friction Courses (OGFC). Odessa's success repeats experiences of California, Florida and Arizona utilizing Asphalt-Rubber.

The crumb rubber generated from discarded shredded tires reacts with the heat from asphalt and forms a durable and flexible binder. Advantages include a increased resistance to reflective cracking, rutting, oxidation as well as better tire to road gripping while reducing noise levels. The Asphalt -Rubber allows for a much thicker asphalt film without the drain down problems of old. This provides much improved adherence of the mix to the roadway which eliminates raveling and pop-outs during cold weather. Also, the increased film thickness should provide for longer life through resistance to oxidation. The carbon black introduced through crumb tires is an excellent retardant and this process puts that aspect to work at full advantage. The cost for Asphalt-Rubber has decreased as well. This decrease is attributed to several factors including the expiration of the patent, associated royalty costs and increased competition. The reported reduction was on the order of about 50%.

Arizona has been a leader in the use of recycled tires, with primary use in Open Graded Friction Courses (OGFC). Of the 7400 mile system, they have about 1500 miles covered with Asphalt-Rubber OGFC. They have depleted their stockpile of waste tires and now importing ties to shred and use. They consume about 5.5 million tons of waste tire rubber per year.

Asphalt-Rubber is the major user of discarded tires. Texas generates over 20 million discarded tires a year. The legislation controlling tire reclamation expired last year. It is likely that will be legislation reintroduced to reinstate the Texas waste tire tax of $2/tire on passenger vehicle and $5/tire for commercial vehicle. The reinstatement of the fee in Texas is supposedly going to help defray any additional up-front costs from using scrap rubber. The outcome depends upon the 76th Legislature.

Please note that Arizona and California have passed laws disallowing tires in landfills. Texas does not allow whole tires in landfills. We are asked at every legislative session about our use of recycled tires.

The Rubber Pavements Association has a wealth of information posted in their Internet site.