The tail end of Manatt’s Paradigm crusher is windrowing the final product, granular subbase, onto a finished shoulder grade. Later, the materials were pulled over the surface and spread out as a subbase.
Iowa’s Interstate 35 rehabilitation project is the showcase resurfacing project in Warren County, funded by money from the American Recovery and Reinvestment Act (ARRA) of 2009.
Just a month after the Act was signed by President Obama, the Iowa Department of Transportation (DOT) let the I-35 rehabilitation project for bid. According to Scott Sommers, Iowa DOT, Chariton resident construction engineer, the overall scope of the project involves total replacement of the existing I-35 pavement from Hwy 34 to the Decatur county line in rural Iowa.
Paving the Way
Toward a Smoother Ride
Interstate 35 stretches from Duluth, Minn., to Laredo, Texas, just short of the Mexican border. Some sections in Oklahoma City were built in 1953 before the interstate system was even created. Other sections opened in 1959, with the final section completed in 1975. Because the original segment of roadway was constructed in the 1960s, it is now in poor condition.
The project is intended to not only extend the life of the roadway, but also provide a smoother ride for motorists and a safer roadway.
“The need for the work was evident in the stressed and oxidized hot-mix asphalt [HMA] overlays and periodic failures of the continuous reinforced concrete as it existed prior to the project,” Sommers said.
This milling and hot-mix asphalt resurfacing project began at the Clarke County line and goes north to Warren County road G-14 south of Cumming. Both the southbound and northbound lanes will be resurfaced. Handled as two contracts the work includes milling, full-depth patching, barrier rail repairs, hot-mix asphalt resurfacing and construction of paved shoulders on an 11.25-mi. (18 km) section of Interstate 35, both northbound and southbound lanes.
Work was divided into two contracts. Manatt’s Inc. of Brooklyn, Iowa, won the bid as the prime contractor on the southbound project, with a $15.6 million contract. The work on this project was started in the spring of 2009 and was substantially completed in late 2009. Approximately 99.9 percent of the overlay work was completed last year. One small section still needs to be modified during the spring of 2010.
Other portions that will be completed in 2010 include: guardrail improvements, sealing of the rumble strips and joint patching. The present estimated completion date is May 2010.
According to Sommers, the southbound project required a high number of six-day work weeks. Chris Swaim, Manatt’s representative, explained that the Iowa DOT gave the southbound project 100 working days to complete. Working days are defined as essentially Monday through Friday as weather allows the contractor to work, he said, adding that Saturdays are not charged, “thus encouraging the contractor to work six days a week.”
After the 100 work days are up, the contractor goes into liquidated damages of $5,000 per day until the project is complete.
“Throughout the project we worked six days a week when the weather would allow it,” Swaim confirmed.
Because last summer had above average rainfall, they began to fall a bit behind schedule, so they implemented two 12-hour shifts on some of their critical operations. This two-week span of working 24 hours a day, six days a week allowed them to regain the time they had lost due to inclement weather.
“At any given time throughout this project we had several crews working simultaneously,” Swaim recalled, “but at the height of the project [late summer] we had over 10 crews with equipment, and more than 100 heavy trucks working throughout the project.”
Flynn Company Inc. of Dubuque, Iowa, is the prime for the $14.5 million northbound contract. Work on this project is scheduled to begin this spring.
The northbound contract is very similar to the southbound: 100 working days to complete and liquidated damages of $5,000 per day beyond that, until the project is complete. Flynn’s Project Manager Mark Gorton anticipated a six-day-a-week schedule dependent on the weather — and on bridgework unrelated to the contract. His crews can not begin until that work is completed.
As he stood by waiting, Gorton knew scheduling could become a race against the clock. Although Sommers said initial preparations were not a hindrance — no right-of-way (ROW) acquisition was necessary, as the same alignment is used for each project, and there were no utility relocation problems — but factors beyond the crew’s control could slow progress once work got started.
Due to the unique interstate paving, workers cannot cross a median to get to the job site.
“Access is one of our challenges,” Morton admitted.
On this second contract, traffic will flow north to south on shifted lanes. Because access to southbound lanes will be closed, trucks leaving the centrally located onsite plant will have to go all the way to the north end of the project, turn around and come back.
“It will be the same roundtrip mileage for all the trucks, no matter how close we are working to the plant.” Morton said additional trucks might be added to keep material delivery arriving in a timely manner, even after they set up a second plant on site.
Once on the job site, crews will employ some time-saving methods.
“A feature that has the potential to be implemented this year with the Flynn Company is the possible full-scale use of ’stringless paving’ that uses lasers and GPS to pave the project,” Sommers stated, adding that it had yet to be fully approved for this year.
Actually, stringless paving, introduced in Iowa last year, uses neither lasers nor GPS. Instead, the paver uses an electronic tracking process from Leica GeoSystems to control the horizontal and vertical operation of the slipform paver.
“We’ll replace two paving hubs spaced 50 feet apart with a control point every 250 feet that’s positioned on alternating sides between the edge of the pavement and the ROW,” Gorton explained. The system gets tied to local benchmarks for accuracy. Three control points are back-sited so the total station knows where they are. Prisms mounted on the pavers will alert the equipment to its location, and an onboard computer will then guide the machine.
Stringless technology offers potential for increasing the application of concrete overlays. Along with advancements in streamlined profiling of the existing pavement, the stringless process eliminates the need for installation and maintenance of string lines, can decrease surveying required prior to placing a concrete overlay and increase smoothness.
“It’s more accurate [than string lines] and smoothness did not suffer,” Gorton emphasized.
The benefits are two-fold: use of stringless paving decreases the appeal of asphalt overlays. With a significant spike in asphalt prices (due to the binder required), demand for concrete overlays has risen. Gorton praised the Iowa DOT, known for its innovation in concrete pavements, for its progressiveness in concrete design that has resulted in a 30-year life for concrete overlay.
“They’ve come a long way in the last 15 to 20 years in pavement, making a product that gives you a bigger bang for your buck than asphalt.”
Another plus is the ease and speed of application. Gorton referred to a recent project in which they paved 18 ft. (5.4 m) per minute on a 5 in. (12.7 m) thick overlay. He estimated that they will be able to pave 6 ft. (1.8 m) per minute on I-35 because it is 11 in. (28 cm) thick. In addition, he pointed out that one person can do the job because the need for setting string is eliminated. That in itself has an added bonus: “It’s used where there are line-of-sight issues.”
“The old pavement was an asphalt-treated base covered with continuous reinforced concrete covered with HMA overlays,” Sommers elaborated. “The new pavement is PCC paving with two separate granular base layers, both of which utilized crushing of the old pavement to specified gradations: a ’special backfill’ for subgrade treatment and a ’granular subbase’ for drainage under the new pavement.”
The composite slab was crushed by subcontractor C.J. Moyna & Sons and reused. In fact, Gorton estimated that 90 percent of the subbase is recycled material: a 12 in. (30.5 cm) layer of a special but non-drainable backfill and an 8 in. (20 cm) drainable granular subbase. Recycling old pavement is increasingly more common and is quite popular with DOTs.
“With a 13 to 14 inch thick base, there’s a lot of material that can be used,” Gorton said.
While the use of recycled pavement may be familiar, the Southbound project was unique because of the use of a rolling “train” to process the existing pavement into the needed rock structures below the new paving, Sommers noted, along with the process to remove the old CRC steel from the old pavement. Swaim claimed that “recycling 100 percent of the old road into subbase material and leaving all material on site” was unusual, particularly because they used a track-mounted mobile crusher that allowed them to pick up the existing road, crush it to the correct size specifications and convey it out the rear into a windrow to be used as new subbase.
However unique the process is, Gorton just hoped it would proceed quickly and without interruption.
“Weather will impact us substantially. Once the old pavement is removed, it will create a bathtub if it rains.”
In order to keep things moving, he planned to have 50 to 75 crewmen on site each day, increasing that number to around 90 once the second plant opens.