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Federal Highway Administration / Publications / Focus / January 1998

Accelerating Infrastructure Innovations

Publication Number: FHWA-SA-98-018
Date: January 1998

Superpave System and Pavement Rehabilitation Prove a Winning Mix at Alabama

The Superpave mix design system is not just for new construction; it's also for rehabilitation projects. That means it's often used over an existing pavement-and even over a base consisting of the rubblized remains of a pavement (see sidebar). The Alabama Department of Transportation (DOT) and the State's local hot-mix asphalt industry recently held a 1-day showcase to share what they have learned about the use of rubblization techniques and the Superpave system on a massive project to rehabilitate a stretch of Interstate 65.

The Alabama Concrete Rehabilitation/Superpave Showcase Project brought together more than 130 people from highway agencies, industry, and Federal Highway Administration (FHWA) offices from as far away as New Mexico to learn about the DOT's project to rehabilitate and widen a 9.3-km (5.8-mi) section of Interstate 65 in Blount County, north of Birmingham. The project involves constructing an asphalt pavement over four rubblized lanes of portland cement concrete pavement and adding two new lanes of full-depth asphalt pavement. At about 220,000 tons (200,000 metric tons) of Superpave mix, the job is the State's biggest Superpave project to date.

When an existing portland cement concrete pavement has reached the end of it's life, highway agencies no longer have to tear it out and cart it away. Using rubblization equipment, agencies can break the concrete into small pieces (ranging from 25 to 50mm [1 to 2 in] at the surface and up to 225 mm [9 in] at the base). This rubble is then compacted to produce a smooth, permeable base for the new pavement.

Attendees spent the morning in the classroom, learning how to determine if the rubblization technique is a suitable rehabilitation option for a project and why a permeable asphalt-treated base and edge drains were used on the Interstate 65 project.

In the afternoon, the attendees trooped out to the project site, where they saw the rubblization equipment in action and the Superpave mix being placed.

Lloyd Strickland of Alabama DOT says the showcase was useful because of the increasing interest in rubblization of concrete pavements.

The showcase also highlighted how industry is leading the way in adopting the Superpave system and other new technologies. It was the contractor, Whitaker Contracting, not the DOT, that proposed using a Superpave mix on the Interstate 65 project. "Whitaker wanted to do the job with Superpave. We felt like we had the personnel and equipment to tackle Superpave," said David Reed, the company's vice president, during a presentation at the showcase.

However, Reed noted, Whitaker Contracting couldn't make the switch to a Superpave mix alone. "What made it work was the cooperation between Alabama DOT, FHWA, and the contractor. The cooperation was unparalleled," said Reed. "By trading information between us, Alabama DOT, and FHWA, we got the information to effectively do the job."

John Davis of the Asphalt Institute, who attended the showcase, says regional showcases are an excellent way to share information about use of the Superpave system. "It goes hand in hand with the goal of FHWA's extended Superpave Technology Delivery Team to bring implementation efforts to the State level," he says.

The showcase was sponsored by Alabama DOT, Whitaker Contracting, the Alabama Asphalt Pavement Association, the Asphalt Institute, and FHWA's Region 4 and Region 6 offices.

For more information, contact Lloyd Strickland, Alabama DOT (phone: 334-206-2335; fax: 334-834-5799).

rubblization equipment in action

Rubblization equipment in action on Interstate 65 during the Alabama Concrete Rehabilitation/Superpave Showcase Project.

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