A concrete overlay project on U.S. 131 north of Grand Rapids, MI, was completed with ease by Ajax Paving Industries, the contractor responsible for paving the job.
“The overlay job in Michigan is the concrete paving industry’s answer to competing with asphalt projects,” Paul Selesky, operations manager of Ajax Paving Concrete Division, said.
“The job was a two-year, 7-mi. project. We overlaid two driving lanes and the existing asphalt shoulders with concrete,” Hugh Luedtke, project manager, explained. “A 1-in. asphalt bond-breaker was applied to the existing roadway. Then, a concrete overlay of a nominal 7-in. was placed.”
The project required that at least one lane of traffic remain open at all times and no traffic crossovers were allowed. Ajax was basically working in traffic.
The first phase consisted of placing the asphalt bond breaker on the existing travel lanes and shoulders, then placing the traffic on the shoulder. The 12-ft. (3.6 m) driving lane with a 10-ft. (3 m) shoulder was constructed. The second phase of the project required moving live traffic to the newly constructed lane and shoulder and adding on a new 12-ft. (3.6 m) lane with 4-ft. (1.2 m) shoulder.
“That’s why we weren’t allowed any crossovers, because it was to be done in the same manner that the asphalt industry would have to construct the job,” Luedtke explained.
The first year of the project, Ajax used its Gomaco GP-3000 paver and manually placed the load transfer baskets. The variable thickness of the pavement required the use of several different size baskets.
“Coordination and delivery of the proper sized baskets was a critical procedure,” Luedtke noted.
The paver was set at 22 ft. (6.7 m) wide to slipform a 12 ft. (3.7 m) driving lane with 10-ft. (3 m) shoulder.
The next year, Ajax brought in its new Gomaco GHP-2800 paver, equipped with the In-The-Pan Dowel Bar Inserter (IDBI), and a Minnich Auto-2 vibrator monitoring system. Placing the dowels in the variable thickness pavement could have been a challenge, but the IDBI handled the insertion process with ease.
“Placing dowels on the run while variably changing the depth of the bar placement was an integral part of the job,” Selesky explained. “It worked out well with the IDBI. Our bar placement was excellent and the owner, the Michigan Department of Transportation (MDOT), was very satisfied.”
The average depth of the concrete was 7.5 in. (19 cm). It would increase in transitional areas and full super-elevation sections.
“At times it was necessary to place more than 2 ft. of concrete on the outside edge, to correct the super- elevation sections,” Luedtke said.
The changes in depth and bar placement were monitored by Ajax and the MDOT. Gomaco has designed special software to allow smooth transitions, and the power transition adjuster (PTA) in the front pan, the IDBI and the finishing pan are all synchronized to make the necessary adjustments as they reach specific stations in the transition.
The computer also can be pre-programmed to skip bar insertion to allow for expansion or other joints.
“The project required a maximum 13-ft. joint spacing,” Luedtke said. “As the paver approached a pre-placed expansion joint, it was a simple process for the operator to override the program, skip the joint and restart the IDBI settings.”
Noting the difference a year can make with the purchase of new equipment, Ajax experienced a dramatic increase in production with its new IDBI.
“The previous year, we used a GP-3000 and set baskets. The next year, with the IDBI, we increased our production approximately 47 percent,” Luedtke said. “Take a look at the job. The location of the haul road was the travel lane and getting trucks in and out as quick as possible was our priority. With the IDBI, we didn’t worry about setting baskets and everything could be done on the fly. The IDBI is the only way to go.”
“Production was a big concern originally when buying the paver,” Selesky explained. “Would the IDBI be able to consistently pave at least 16 ft. a minute? We discovered the IDBI cycle, at times, can pave faster than that.”
The accuracy of the bar placement is tested often and Ajax has had excellent results. Depth of the bars and consolidation around them is carefully checked.
“Typically at night, we would construct two to three test headers that we’d place dowel bars in,” Luedtke said. “The dowel bars were 1.24 in. in diameter and 18 in. long. Cuts were made 2 to 3 in. from either end to expose the bars so placement and consolidation could be checked. Results from our tests consistently passed all MDOT requirements.”
Selesky added, “After observing the quality and productivity on this project, some MDOT personnel have come to realize that dowel bar insertion is superior to any type of manual basket setting operation.”
For more information, visit www.gomaco.com.
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