GOMACO World Index --- GOMACO World 44.1 - November 2016

Slipforming Success with the New GOMACO GP3 Concrete Paver



Swank Construction Company has a long-time roadbuilding history, and they chose the GOMACO GP3 with Trimble 3D guidance for their mainline paving projects around the Pittsburgh area of Pennsylvania.


Swank Construction Company
New Kensington, Pennsylvania

Swank Construction Company has a long and prestigious history in and around the Pittsburgh, Pennsylvania, area. They are a fourth generation family-owned construction company that traces their roots back to approximately 1930.

“No one knows exactly when we started, but we’re pretty sure around 1930 my great-grandfather started business with a mule and a wagon full of bricks,” Andrew Swank, an owner of Swank Construction, explained. “Most of our time has been as a concrete road and bridge constructor, so through the history of American roadbuilding, we’ve been there.”

It wasn’t until recently though, that the company decided to get into the concrete slipform paving market. They meticulously did their research on concrete slipform pavers and their different features. They knew they wanted a 3D machine guidance system with it and the paver needed to be versatile, easy to transport, and able to work in tight-clearance conditions.

After comparing the various pavers and each of their attributes, Swank Construction ultimately narrowed down their search to the new GOMACO GP3.

“Travis Brockman, our GOMACO district representative, and the whole GOMACO group were amazing and just blew everybody away, to be honest,” Swank said. “They talked a big game in the sales pitch, which all salesmen do, but Travis has backed it up and so has the rest of his team. They’ve been out here since day one helping us, getting us familiar with the machine. It’s been fantastic so far.”

Swank Construction’s GP3 was delivered right to the project at the intersection of Interstate 376 and the McClaren Road, Exit 4, in Pittsburgh. Swank is reconstructing five miles (8 km) of both the eastbound and westbound lanes of the interstate, which is the main access road to Pittsburgh International Airport.




No stringline is necessary on Swank’s project. The paver is sensing off the existing slab for elevation control on this add-on lane and the G+ controller maintains the four percent cross slope.



A steer wand sensing off a steel plate bolted to the back leg of the GP3 controls rear steering and grade. The GP3’s two right-side legs are locked to grade.




The new three-lane roadway will be completed in different paving widths ranging from a 15 foot (4.6 m) wide shoulder, to a 22 foot (6.7 m) wide pass which includes a 12 foot (3.7 m) driving lane with 10 foot (3 m) shoulder. The company has also purchased an IDBI attachment to insert transverse joint bars in the new pavement on-the-go. The GP3 with IDBI will be paving 24 feet (7.3 m) wide. All of the pavement is 11 inches (279 mm) thick.

The GP3 has been equipped with a Trimble Navigation Ltd. 3D machine guidance system eliminating stringline from the project. In fact, the whole project is being constructed using the Trimble system, from milling to grade preparation to final concrete paving.

During construction, traffic flow must be maintained on the major artery into the city. Swank Construction began work on the westbound lanes of Interstate 376 earlier this year. As traffic continues to flow on two existing lanes of the interstate, they have removed and are replacing the existing inside shoulder, the first phase of the project. The new roadway is being built to last from the ground up.

“There’s 24 inches (610 mm) of stone with a four inch (102 mm) asphalt permeable base placed over the rock,” Lou Schultheis, Construction Manager for Swank Construction, said. “We put 11 inches (279 mm) of concrete on top of that, three lanes wide for five miles (8 km) east and five miles (8 km) west.”

Concrete for the project is a Pennsylvania Department of Transportation (PennDOT) double A mix with a slump averaging two inches (51 mm). Swank’s batch plant is located approximately 12 minutes away and concrete is delivered in tri-axle dump trucks, each carrying a 12 cubic yard (9.2 m3) load. The concrete is dumped directly onto grade in front of the GP3 slipform paver.

The GOMACO GP3 is equipped with a 5400 series paving mold featuring a 54 inch (1372 mm) finishing length from front to back, edge slump adjustment, and a self-supported transition adjuster (TA). The 5400 series mold also has hydraulic vertical hinged sideplates that are self-contained inside the mold for track clearance.




Swank’s GP3 paver is equipped with a GOMACO 5400 series mold with a self-supported transition adjuster (TA). The 5400 series mold is also equipped with hydraulic vertical hinged sideplates for track clearance on this project with tight-clearance paving conditions.



When scab-on paving, the GP3’s steering wand on the front of the paver is sensing off the existing slab for grade and steering.




“We decided on the GP3 because of the stringless and the paver just seems more advanced, more maneuverable. This job has a lot of tight applications and tight quarters,” Pete Douglas, Superintendent for Swank Construction, said. “For this first phase, we only have about 2.5 feet (0.8 m) from existing edge of old concrete to new concrete. We need just enough room for the track to fit. The pivoting legs and the GP3 come in handy.”

Trimble’s PCS900 paving control system uses total stations, sensors on the paver, and their software to guide the GP3. The 3D model of the construction site is prepared using their Business Center - HCE software. It has a virtual “drive through” feature allowing contractors to address any potential issues with the model before concrete paving begins. Swank uses three to four total stations to control the alignment of the paver during slipforming with precise millimeter control of the mold. When it’s time to switch from one total station to the next, the system will automatically and instantly transition to the next total station. The feature is called a “hot swap” and there’s no need to stop the paver. The same tolerance between total stations is automatically maintained for a smooth transition from one point to the next.

“We’ve been trying to keep total station distance around 300 feet (91.4 m), but we have a lot of light poles along here and they become a giant obstacle when you start setting the guns up,” Douglas said. “More often than not, we find ourselves putting the guns a lot closer just because of obstacles. Our surveyor stays busy just because we don’t have the luxury of open real estate beside us. It’s a rehab, not a new job.”

PennDOT uses the International Roughness Index (IRI) as their standard for pavement rideability. The specification requires an IRI of 70 or below. Anything over 70 requires corrective action. The GP3 is equipped with mold-mounted GSI® (GOMACO Smoothness Indicator) units constantly measuring and reporting the smoothness of the new pavement.

“We were in the 30s last week,” Douglas said. “We’re milling subgrade with the Trimble system on our model and we’re seeing each layer come back flat and nice and it’s coming back in the ride. I’ve only worked around stringline before, so it’s all new to me. I am extremely impressed.”

Swank can monitor their GSI readings, along with Trimble 3D and G+ information all from ground displays located within eye level of personnel. The G+ features a remote operator’s screen with the same graphical display as the operator’s station. It’s called G+ Ground Control and allows ground personnel to see everything on the screen that the operator does on top of the paver. Ground Control also gives them the ability to fine tune the paver and make settings adjustments.



G+ ground control

G+ Ground Control is available on the GP3. It’s a remote operator’s screen that can be positioned anywhere on the paver and allows the ground crew to see the same image that’s on the G+ controls at the operator’s station. The crew can monitor their GSI readings, Trimble information and G+ operating status. Ground control also allows the ground crew to fine tune the paver and make adjustments to the settings.


G+ ground control

The GSI smoothness readings can be viewed on the GSI display (right monitor), as well as on the new G+ Ground Control display screen (left monitor).




“Typically we have the three boxes on the side of the paver,” Douglas explained. “We have the box that’s basically the reflected image of what the operator sees, which we have some control on that. Then, we have the Trimble box which is all run from the ground, trading guns on and off, and then we have the GSI box for the ride spec.”

Portions of the 15 foot (4.6 m) wide shoulder with four percent cross slope are scabbed onto the existing two lane roadway. Even for the scab-on work, Swank Construction is remaining stringless. G+ controls allows them the added versatility with various sensoring capabilities.

“We’re running grade and steering off the existing slab and running cross slope with the paver locking the other two legs,” Douglas explained. “We’re actually running off sensors, no stringline. We have a sensor on the slab and then we took a steel plate, bolted it to the back leg, and that runs our back grade and the back steering.”

A GOMACO T/C-600 texture/cure machine follows the GP3 applying a longitudinal tine and white spray cure. Wheels attached to the sensors on the texture/cure machine allow steering to be referenced off the side of the new slab and grade control to be referenced off the top for this stringless project.

The new concrete slipformers are quickly becoming experienced veterans as they continue the shoulder work on the project and progress to the driving lanes and eventually outfit their GP3 with the IDBI attachment. The GP3 and its versatility has proven itself already in the tight project conditions. It’s transportability has also been a major factor. Even though it hasn’t moved off the interstate, it’s been loaded up and moved several times along the length of the project.

“One of the big problems with this project is it’s so broken up and all over the place,” Douglas said. “We have actually spun the paver, walked it up on a lowboy with the mold under it, moved it, and poured the same day with it because there’s really no set up. Spin it, set it, set your guns, and away you go.”




The GOMACO T/C-600 texture/cure machine has wheels attached to the sensors to steer it on the stringless project. Steering is referenced off the side and grade control is referenced off the top of the new concrete roadway.



The T/C-600 machine applies a white spray cure and longitudinal tine finish to the new Interstate 376.




Swank Construction’s GP3 paver is the third one manufactured by GOMACO, with serial number 912600-003. Sometimes, the company has hesitated in the past with buying a new model.

“I have hesitated before buying the newest model of something, but didn’t really hesitate here except maybe in the back of my mind and thinking I hope this thing works fine just like the rest of the GOMACO fleet,” Swank said. “If they’re selling you, they’re being honest with you. They do follow through. They’re not blowing smoke. It’s been great and we’re probably still rookies, but we’re fast turning into experienced pavers now. We’re getting down the road.”





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