The right choice

Warm mix excels on one of Florida’s most challenging highway design-builds

Amy Chiconas / August 29, 2018
I-95 widening

Interstate 95 (I-95) is the main interstate highway on the East Coast of the U.S., running for almost 2,000 miles.

The state of Florida sees 382 miles of I-95 pass through its borders, where the southernmost portions transport traffic along the state’s Atlantic coast. The Florida Department of Transportation (FDOT) needed to increase mobility and connectivity at the I-4 and U.S. 92 interchange, also known as International Speedway Boulevard. FDOT began a $205 million widening and systems interchange reconstruction and design-build project in the spring of 2015. This three-year project was no easy feat.

This project involves widening I-95 from four lanes to six lanes from north of S.R. 44 to north of U.S. 92. The southern project limit will tie into the recently completed I-95 widening project to the south (from south of S.R. 406 to north of S.R. 44). The project scope also includes the reconstruction of the systems interchange with I-4, I-95 and U.S. 92.

FDOT awarded the project to international general contractor Archer Western Construction. Archer Western is one of the largest mass transit and bridge contractors in the U.S., and is ranked by Engineering News Record as the 12th largest mass transit and rail contractor in the country. They partnered with P&S Paving of Daytona Beach when it was time to widen and realign a 140,000-ton portion of the road. P&S has a 21-year history of paving projects as a licensed general contractor in the state of Florida, and participates in large highway reconstruction projects regularly.

Overall project improvements ultimately included drainage system enhancements, signing and pavement markings, milling and resurfacing, intelligent transportation system modifications, highway lighting, bridge widening and replacement, retaining walls, signalizations, median barriers and, of course, pavement widening.

Considerations and challenges

The 140,000 tons constructed by P&S Paving required significant planning. There were 18 bridges along the 14-mile project that were widened or replaced, one of which was raised 3 ft in order to make way for a future rail network. Scheduling also was a key concern because the project was to take place over a three-year period on I-4, which is a major artery.

Uninterrupted access to a heavily trafficked project location was an additional consideration. Daytona Beach is home to NASCAR and the Daytona International Speedway is only yards away from the project site. This called for careful coordination efforts between project management, FDOT and racetrack officials in order to accommodate events during the racetrack’s annual Daytona Speedweeks and Daytona Beach’s Bike Week, events that draw upwards of 500,000 visitors to the area.

Roadway texture, density and rideability also were highly important issues to address. The project’s location in Florida and close proximity to ocean breezes, as well as paving during winter months, all presented challenges to achieving acceptable texture, density and rideability. Thus materials selection was a crucial factor in achieving project success.

“The recent I-95 rebuild was a huge opportunity for us,” explained Tim Carter, director of quality control at P&S Paving. “We chose warm mix asphalt for this job because it provided the flexibility, opportunity for pay factors and liquid anti-strip properties that we needed on such a large and challenging project. Moreover, using a warm mix additive as part of this job greatly simplified life and helped us guarantee success on a very high-profile highway project.”

P&S Paving

P&S Paving set up a state-of-the-art facility to serve the project site.

Structural course materials

Both the structural and friction course designs of the project utilized Georgia granite and contained PG 82-22 polymer modified asphalt (PMA) and PG 76-22 PMA liquid components. The liquid binder also included 0.5% Evotherm M1 warm mix additive.

The structural course mix designs used on the project were 12.5 mm mixes. Georgia blue granite stone materials comprised the majority of the aggregate skeleton of the mixes, with 20-45% fractionated recycled asphalt product (FRAP) making up the rest. Maintaining volumetric properties and the quantitative targets set forth in the mix designs approved by FDOT also were an ongoing consideration.

Friction course materials

Archer Western designed the project to include an open-graded, bonded friction course (Florida’s FC-5 mix) to shed water along the highway. A PG 82-22 binder was specified for its rut-resistant qualities. PG 82-22 mixes are often used on Florida bus pads in order to mitigate shoving and deformation amidst heavy loads in the sunny, hot climate.

All open-graded friction course (OGFC) designs were required to be constructed of 100% virgin materials. Dense-graded friction course designs were allowed to contain up to 20% recycled materials.

Construction

The widening areas of the project typically received 3.5 in. of a 12.5 mm structural, non-modified mix that were placed in two 1.75-in. lifts. This was followed by a 1.5-in. lift of a 12.5 mm PG 82-22 PMA structural mix, and was then topped with 0.75 in. of FC-5 PG 82-22 PMA OGFC mix.

Temperature requirements for placement of the OGFC were a minimum of 65°F, or 60°F if approved by the engineer and absent any texture issues. Temperatures could be further reduced to approximately 55°F with the use of warm mix asphalt (WMA).

“We used M1 in every mix ton we produced,” said Carter. “This allows us great flexibility. Since the additive is already included in the liquid components of all mixes, we can switch to a warm mix version of any mix design. The switch is seamless and extremely efficient with regards to production. This translates directly into profitability for the contractor.”

The composite pay factor averaged 102% for the overall project. The target for roadway density was 93% and was typically achieved using Sakai and Cat rollers at 15-20 tons operating in the vibratory mode. Pay factors for density averaged around 104%. Receiving a 4% bonus for density was typical for the job.

“On this project in particular,” said Carter, “PG 82-22 and PG 76-22 PMA were both used for structural lift asphalt. A warm mix additive allowed for additional workability time, which was a tremendous help to achieve this goal.”

I-95 wrap-up

The I-95 project is on target to wrap up this coming fall.

Testing and production

P&S Paving’s Daytona Beach facility includes a state-of-the art quality-control laboratory that was updated as recently as 2015. An on-site quality-control team ensures that the highest quality standards are met and maintains the laboratory’s annual CMEC lab accreditation program.

They also own a new $5.2 million Astec double-barrel drum. The new plant facility features a separate pug mill mixing unit, a hot-liquid calibration tank and plant controls that provide a button-free operational environment for the operator. P&S has an additional FRAP plant that produces two materials consisting of course and fine FRAP, respectively. These materials are then used directly as components of the hot mix asphalt and WMA produced on-site.

Stockpile management is a key element in maintaining a consistent flow of P&S materials used in production. This element was especially important on the widening project.

“Our utilization of a warm mix additive has been a natural evolution of our stockpile management process,” said Carter. “It provides more efficient and effective coating of the virgin aggregates in the drum and through to the mixing chamber.” Stockpile management for both FRAP materials and virgin aggregates also helps to ensure optimum quality throughout production. P&S has a paved stockpile area and uses gravity to remove unwanted moisture from the piles.

A warm mix win

“I don’t even want to imagine what this project would have looked like without [our mix choice],” said Carter. “There is simply no room for errors or the delays typically associated with switching from hot to warm mix jobs. Especially on a project of this magnitude. We get flexibility and consistency with an additive, and it’s why we’ll continue to use it in every mix ton we produce [on this project].”

As of this writing, crews are on target to meet a fall 2018 project completion deadline and get those new lanes open and ready to roll.

About the Author

Chiconas is with Ingevity.

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