Subcontracting the Barrier Wall and Curb and Gutter
PRC is utilizing approximately 30 different subcontractors on the I-15 CORE Expansion to complete various aspects of the project. Two of those contractors, Harper Concrete, out of Draper, Utah, and RGG United Contractors Inc., from Glendale, Arizona, are slipforming 61 miles (98 km) of barrier wall and 25.5 miles (41 km) of curb and gutter.
Here’s how those quantities break down:
- Roadside barrier: 216,528 linear feet (65,998 m)
- Median barrier: 105,576 linear feet (32,180 m)
- Type B1 curb and gutter: 38,636 linear feet (11,776 m)
- 24 inch (610 mm) curb and gutter: 32,489 linear feet (9903 m)
- Type B5 median curb: 17,451 linear feet (5319 m)
- Type m2 (mountable curb on PCCP): 5150 linear feet (1570 m)
- 24 inch (610 mm) mountable curb: 1290 linear feet (393 m)
- 28 inch (711 mm) rolled gutter: 10,375 linear feet (3162 m)
- 36 inch (914 mm) rolled gutter: 20,352 linear feet (6203 m)
- 4 foot (1.2 m) rolled gutter: 5828 linear feet (1776 m)
- 4.5 foot (1.4 m) rolled gutter: 2929 linear feet (893 m)
Harper Concrete has been at work since the early days of the project slipforming the barrier with their GOMACO three-track and four-track Commander IIIs. They are slipforming all of the curb and gutter with their two GOMACO GT-3600 curb and gutter machines.
“We are slipforming median barrier anywhere from 54 inches (1372 mm) to 9.5 feet tall (2.9 m) and a roadside barrier that is a standard 42 inches (1067 mm) tall,” Josh Harper, Estimator and Project Superintendent for Harper Concrete, explained. “The real tall wall we’ll do in two separate stages. We slip the bottom half first and then come in and cap it with the 54 inches (1372 mm) to create a 9.5 foot (2.9 m) tall wall. It’s pretty impressive.”
Harper Concrete has one GOMACO barrier mold that slipforms both the 42 inch (1067 mm) and 54 inch (1372 mm) wall. The mold is equipped with sideplates that have up to 18 inches (457 mm) of hydraulic adjustment for height changes. It gives them the versatility to slipform different heights without switching out molds. The front of the mold is equipped with seven flutes for rebar guides. Seven strands of steel rebar have to be continuously inserted into the mold for reinforcing in UDOT’s barrier wall.
The concrete mix design is a 6.5 bag UDOT-approved mix with a 4000 psi (27.6 MPa). It contains manufactured sand and fly ash. Slump averages 0.5 inch (13 mm) when slipforming barrier.
“The four-track Commander III is nice because it’s big enough to handle the taller wall, but it’s not too big,” Harper explained. “The three-track Commander III is nice for turning a sharper radius and it makes getting around obstacles a lot faster. Both of them slip straight, flat wall.”
Harper uses stringline on their work. They use recycled car rims, weld one-half of a stringline stake to it, to create a lightweight and easy-to-place stringline holder. They run the stringline underneath the paver, between the tracks.
Roadside barrier production averages approximately 1000 feet (305 m) per day. Median barrier production varies depending on the height. At 54 inches (1372 mm) tall, production will average between 800 to 900 feet (244 to 274 m) per day.
A crew of five to six finishers work behind the Commander III. They saw-cut joints into the wall at 15 foot (4.6 m) intervals to match the joints in the new roadway.
Along with the barrier wall, Harper is also responsible for the curb and gutter on the project. The majority of the curb and gutter is being slipformed at the project’s interchanges.
Harper is using their two GT-3600 curb and gutter machines to slipform the different profiles of curb and gutter. None of the figures along the I-15 seem to be small. When Harper talks about the amount of curb and gutter they’re slipforming on the project, it’s not in feet, it’s referenced by miles.
“We’ll be slipforming approximately 25 miles (40 km) of curb and gutter on the project by the time we complete,” he explained. “All of it completed with our GT-3600s.”
The concrete mix design for the curb and gutter is the same as the barrier wall. Slump is the only difference, averaging 1.5 inches (38 mm).
“Our guys can do basically any type of concrete work that is needed or can be done,” Harper said. “They can go one day from barrier wall to the next day curb and gutter. We have a really great bunch of guys. We’ve been out on this project since it started and we’ve put down a lot of concrete.”
RGG United Contractors Inc. is also at work along I-15 slipforming the different barrier applications. They are using their GOMACO three-track Commander III and GT-6300 to complete their portion of the work. They have one barrier crew that moves from machine to machine for each day’s pour.
They are at work on the standard 42 inch (1067 mm) tall roadside barrier, and also the 54 inch (1372 mm) tall median barrier. They are inserting the same seven strands of steel reinforcing as Harper Concrete.
“On barrier like this, we like to use a one inch (25 mm) maximum slump on the concrete,” Raul Rodriguez, Superintendent for RGG, said. “Our average production varies, depending on the weather, the concrete supply and on the crew performing well. Our machine is running good and producing a nice barrier with very little finishing work.”
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RGG United Contractors Inc. uses their GOMACO three-track Commander III to slipform their portion of the 322,104 feet (98,177 m) of barrier wall on the I-15 project.
Harper Concrete is using both a three-track and a four-track Commander III to slipform their portion of barrier wall along the new stretch of interstate.
There are 61 miles (98 km) of roadside and median barrier wall to complete along the project.
Two GT-3600s are slipforming the project’s 25.5 miles (41 km) of curb and gutter.
UDOT requires seven strands of continuous steel reinforcing in the wall. The barrier molds are equipped with seven flutes in the front to allow for the insertion of the steel.
Barrier production averages between 800 to 900 feet (244 to 274 m) per day when slipforming the 54 inch (1372 mm) tall median barrier with the three-track Commander III.