The GHP-2800s with IDBI Attachments
PRC is using two GHP-2800 four-track pavers with IDBI attachments on the I-15. They are slipforming mainline passes of 24 to 26 feet (7.3 to 7.9 m) wide. The IDBI attachment is inserting bars for the transverse joints every 15 feet (4.6 m). Bar spacing and dimensions are the same as the GP-4000 with IDBI attachment.
“This is a producing machine,” Preston said of his crew’s GHP-2800. “For a full week, we slipformed just under 4000 cubic yards (3058 m3) each day and that was with the IDBI. We were paving 26 feet (7.9 m) wide and 12.5 inches (318 mm) thick, inserting 10 bars per lane. Our best production reached 5900 cubic yards (4511 m3) in one day.”
Smoothness for the GHP-2800 with IDBI attachment has an average PI of between two and three inches (51 to 76 mm), but has reached a PI of zero on long paving stretches. Preston credits good ride numbers to proper paver maintenance and keeping a consistent roll of concrete inside the IDBI.
“The better you keep that roll, the more consistent your profile is going to be,” he explained. “A good roll is also important for proper consolidation around the bars. I like to see the roll a little bit larger than a volleyball, probably about the size of a kickball. I’ve always said, too, that I like to see the concrete rolling.
“We have done a lot of bar placement checks. We’re cutting joints for depth and use a sonar scanner to find out how parallel the bars are to the top of the surface. We’ve done very well. The depth has always been consistent and the alignment has been very accurate.”
The paving crew does a lot of mainline with the GHP-2800, and the project has presented some challenging situations for them to pave through.
“We were paving in an area called the S-Turns with a pretty good superelevation of a five percent cross slope,” Preston explained. “We had to keep the paver on that slope, going around a radius while keeping a good, consistent roll in the IDBI. The area also had three consecutive bridges that we had to tie into, jump, and continue paving. It was challenging, but interesting as well, to keep the paver and the concrete doing what it needed to do. The GHP-2800 handled it very well.”
“The bridge tie-ins are one of the most taxing things we have to do with the 3D system,” Reggie Schlieper, Field Engineer, said. “We want them to be perfect, so we go out of our way to make sure we know what the deck is and we know what our slab is behind the paver so we can hit that tie-in perfectly.”
When not on mainline, they have the option of removing the IDBI attachment from the paver and slipforming ramps, side streets and other areas of the project.
“The GHP-2800 has definitely been used for a lot of different paving,” Preston said. “We’ll drop the IDBI attachment and do shoulder paves to mainline to ramps to streets at different thicknesses.
“The IDBI attachment is my favorite feature on the paver. With its own engine on the IDBI, itself, and its modular design... it’s very effective to take off the IDBI and attach it back onto the paver so we can do what we need to do.”
The Two-Track GHP-2800
Of all the pavers on the I-15 project, the GOMACO two-track GHP-2800 probably has the most mileage on it. It has been moved up and down the 24 mile (38.6 km) stretch of interstate nearly every day, slipformed some of the most challenging tie-ins, and in general, has been the go-to paver on the project.
“The fantastic thing about the two-track GHP-2800 is it’s very easy to move,” Steeves said. “You can drive it right up onto a trailer and transport it. We move that paver almost every night, or when they’re paving nights, we’ll move it every day. That makes it very versatile.”
“We do a lot of the lane and shoulder taper pave passes, ramps, and even mainline, so we’re pretty versatile,” Brian Spahr, Paving Superintendent for the two-track GHP-2800, explained. “That’s the great thing about the two-track. You can pave in one spot, load up, and be paving in another area the next day.”
The GHP-2800 slipforms passes 24 to 26 feet (7.3 to 7.9 m) wide on a variety of applications. Baskets, with 15 foot (4.6 m) joint spacings, are placed on grade in front of the paver while the GOMACO 9500 places the concrete.
“An important area where we utilize this paver is on ramp transitions where there will be an auxiliary ramp already established on mainline that veers off to an exit,” Steeves said. “It will become a two-lane exit with a second lane evolving off the mainline. The GHP-2800 will drag 12 foot (3.7 m) of pan for a short distance and then turn and start paving the 24 foot (7.3 m) wide ramp.”
All of this is accomplished with 3D guidance on the paver. The ramp work also includes radii. Tight radius work normally isn’t associated with slipform pavers and involved a bit of a learning curve to slipform them effectively and smoothly with the Leica system.
“At first we had some issues holding the radius,” Spahr said. “We found that by moving our tick marks from the left or the right and running them down the center line made it less octagonal. We’ve also learned to hold the tick marks a lot tighter on the model and we’ve been doing very good with our radii since then. We’ve turned a radius with a 50 foot (15.2 m) center line and the paver handled it really well.
“The Leica has really given us a lot of other advantages, as well, with phasing, maneuvering around obstacles, and we’ve gotten a great ride out of it.”