Open highway: progress is steady toward the increased use of recycled aggregates in paving materials.

Resistance to recycling old sections of highway back into material that can be used in new roadways does not stand up to logic, according to J. Don Brock, chairman of Astec Industries, Chattanooga, Tenn.

"It's the same age, whether it's been in a rock quarry or in a road," the corporate chairman said at a seminar on asphalt and concrete recycling held at the 2005 ConExpo-Con/Agg event.

Brock advised attendees in the paving and highway engineering fields not to look at recycled aggregates as a second-hand product and touted advantages that recycled concrete and recycled asphalt can offer.

COST EFFECTIVE

The rise in oil prices has changed the way a number of business managers think and operate in the past two years, and pavement contractors are no exception.

On the job site, hauling material in and hauling it away has become more expensive as fuel prices rise, providing a clear reason to consider on-site crushing and reuse of old highway sections.

Brock provided several examples of formulas demonstrating how the use of recycled materials is cost effective for highway contractors, particularly when hauling costs can be subtracted.

In the asphalt sector, the rising price of oil has provided double the incentive because recycled asphalt pavement includes some of the oil additive that otherwise would have to be purchased at escalating costs.

That oil additive was once considered "a residue that oil companies used to give away," Brock commented. But those days are long gone, he stressed, and now any oil that can be recovered from recycled asphalt presents a tremendous opportunity.

In the asphalt paving sector, "Recycled products are worth what they replace plus any disposal fee [and] minus the processing cost required to get the material into the hot mix asphalt plant," Brock told attendees.

In terms of quality concerns, Brock said that advances in processing and screening equipment have dramatically improved the ability of recycled materials to meet a specification. "We can now make a better recycled concrete aggregate product with segregated sizes."

The chairman of the multi-national crushing and paving equipment company came out forcefully in favor of recyling by stating to attendees, "There is not any equipment we can sell you that could save you as much money as using recycled materials."

STATE OF THE STATES

ConExpo attendees also had the opportunity to hear Charles Luedders of the Federal Highway Administration provide a summary of a five-state study the agency conducted on advanced uses of recycled concrete aggregate (RCA).

The 2004 study (summarized in "Choice Cuts," January/February 2005 Construction & Demolition Recycling, Pages 20-24) examined how and to what extent RCA was being used in California, Michigan, Minnesota, Texas and Virginia.

The study determined that Texas is "a large user of RCA materials," with private industry and municipalities consuming more than 60 percent of the RCA produced in the Lone Star State.

The Texas Department of Transportation (TxDOT) has approved the use of RCA in its highways for 10 years, finding engineering, economic and environmental benefits.

The agency acknowledges some initial hurdles that it had to overcome, including "problems with mix workability," according to Luedders. "Contractors overcame this hurdle by [modifying] their process control program.

The FHWA report notes that TxDOT has 'performed training and continually presents information to its districts concerning the performance of the projects it has completed around the state."

The Virginia Department of Transportation (VDOT) has worked "to provide a neutral playing field for recycled and virgin aggregates," according to the report. Additionally, VDOT has established an income tax credit on the purchase price of recycling machinery, though it is restricted to fixed plants and does not include mobile equipment.

The use of RCA is permitted by the Michigan Department of Transportation (MDOT) specifications, with the agency's strategy being to permit use "if it enhances or equals the performance of virgin material in the final product."

Permissible uses for RCA in Michigan include as aggregate within Portland cement concrete poured for curbs and gutters, sidewalks, barriers, driveways, temporary pavement, interchange ramps and shoulders. In hot-mix asphalt, the material can be used as aggregate for base course, surface course, shoulders, approaches and patching.

The Minnesota Department of Transportation (Mn/DOT) requires a 60-year pavement design life on its high-volume freeways and a 35-year design life on other highways. "The factors have contractors shying from [RCA's] use in the concrete pavement, since the belief is aggregate washing would be required to produce usable aggregates," the report notes.

According to information provided by the California Department of Transportation (CalTrans), "Most of the concrete pavement removed from existing highways and streets in California is processed and used as aggregate base throughout the state."

Using RCA as part of a concrete pavement mix appears to have little historical backing from CalTrans. The report notes that the city of San Francisco is developing a specification that permits RCA's use in concrete curbs, gutters and sidewalks.

The study concludes that 38 states are using RCA as an aggregate base, but just 11 are putting RCA back into Portland cement concrete.

The study's conclusion hails Texas as "a leader in the use of RCA as an aggregate in concrete pavement" and says the state provides "an illustration of how recycled concrete aggregate can be reused as an aggregate in a quality concrete pavement surface."

IN DEMAND

Cecil Jones, a materials engineer for the North Carolina Department of Transportation and also chair of the American Association of State Highway Transportation Official's (AASHTO) task force on recycled materials, also addressed attendees of the same ConExpo session.

AASHTO, which includes most state departments of transportation as members, writes standards that are used by DOTs and many municipalities across the country.

Jones told attendees he sees the task force's work as vital, since it will "help extend the limited [aggregate] resources that exist." Jones also noted, "It's very difficult to open a new quarry ... even to expand is difficult."

The AASHTO task force is committed to maintaining quality standards first and foremost, said Jones, but is also intent on allowing contractors to tap into the tipping fee savings and the large volumes of material that can be theirs when they use recycled aggregates.

Finding the balance between advocating innovation with the "cautious nature" of highway engineers will be the task force's challenge, Jones acknowledged.

The task force will work with the Recycled Materials Research Center at the University of New Hampshire to ensure testing and scrutiny of any new specifications.

He also said that the environmental stewardship angle is important to him and to other task force members. "It's the right thing to do," Jones said of concrete and asphalt recycling.

As it already stands, concrete and asphalt industry spokespersons make claims that their material is "the most recycled material in the world," based either on percentage (asphalt pavement) or volume (concrete). "We don't publicize that enough," Jones said.

The author is editor of Construction & Demolition Recycling and can be contacted at [e-mail].