Slipforming successful wall, according to P.T. Ferro, is having the right concrete mix design delivered at the correct slump.
P.T. Ferro Construction Company started in 1964 as a utility contractor in Joliet, Ill. Since that time, it has taken on a variety of challenges as it has expanded its business. P.T. Ferro added a GOMACO GT-3600 curb and gutter machine in 2004 and started slipforming curbs on its projects.
The Illinois Department of Transportation (IDOT) let a barrier wall project on Interstate 55, just west of P.T. Ferro’s Joliet location. The company had never slipformed barrier wall before, but wasn’t afraid of the challenge. P.T. Ferro consulted with its GOMACO distributor, Finkbiner Equipment Company, and with GOMACO engineers to find the right machine and mold profile to complete the 22,000 lineal ft. (6,706 m) of variable height, center median barrier.
P.T. Ferro purchased a Commander III with a four-track barrier package assembly. The mold was built with double variable capabilities so each side of the wall could be adjusted up to 30 in. (76.2 cm) to meet project specifications in a single slipforming pass.
Choosing the right machine was an important decision in the project’s early phase. P.T. Ferro was working under a tight deadline for completing a portion of the work before winter weather moved in.
“This job had an interim completion date that included a penalty,” Phil Hess, president of P.T. Ferro, said. “We were under the gun to buy a machine, and get 2,500 feet of barrier wall slipformed before winter set in.”
The new Commander III was delivered on time on Oct. 22. The project’s completion date for the year was Nov. 15. The completion date included not only finishing the barrier wall, but also the entire project of adding a new lane and opening up that section of interstate to traffic again.
“Once the Commander III arrived, we only needed a couple of days of training,” Eric Zola, general superintendent of P.T. Ferro, said. “The operating systems on the GT-3600 and the Commander III are very similar, so it was easy for our people to learn. Because of the background we already had and the ease of using the GOMACO equipment, I’d say we were up to maximum production within a couple of days.”
On the first day of the barrier pour, IDOT had a review team onsite to witness the slipforming.
“They were impressed with the quality of our wall and our total production,” Zola explained. “And it was just our first day. It only got better from there on out.”
The barrier’s profile featured a 39.25-in. (99.7 cm) wide base, and a 19-in. (48.3 cm) wide top, with both of the sidewalls varying in height from 3.5 to 6.5 ft. (1.1 to 2 m). Every 14 ft. (4.3 m) of wall required a new mixer truck, carrying a 10 cu. yd. (7.6 cu m) load of concrete.
“In a normal work day, we always exceeded our estimated production rates,” Zola said. “We were emptying concrete trucks every 14 minutes… that’s a lot of concrete. Our concrete supplier, Welsch Ready-Mix, did an excellent job for us.
“The key was getting the concrete to the site at the right slump, having the vibrators set correctly and then just having great personnel out there.”
The concrete mix design was an IDOT approved mix with slump averaging between 0.5 to 0.75 in. (1.3 to 1.9 cm). P.T. Ferro used nine straight vibrators placed at strategic locations in the barrier mold. P.T. Ferro also equipped its Commander III with a 24-in. (61 cm) long conveyor extension. Zola felt the extension made it easier to get concrete from the trucks into the mold to aid the overall production rate.
Finishing work was kept to a minimum with only a light broom finish applied behind the Commander III.
P.T. Ferro finished its first portion of interstate within the time allowed. It went back and completed the second portion of the project and impressed everyone at IDOT with its slipformed barrier.
“It was a massive wall within a restricted area, but it worked well for us,” Hess said. “From Marty Ahrendt at Finkbiner Equipment to GOMACO… everybody was just top notch.
“The key, besides the equipment and the people, is good concrete… The concrete is crucial. Because of this experience, we’re looking forward to doing more wall work with our Commander III in the near future.”
This story was reprinted with permission from GOMACO from its GOMACO World magazine, Vol. 37, No. 1. CEG