Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85902
Applications&Innovations feed, the slump and more," Peace explains. "We would make notes as we made changes and just kept tweak- ing until we reached where we needed to be. The instant feedback from the GSI was a good thing. It gave us the knowledge of what the con- crete was doing in regards to the changes we were mak- ing. We could see right on the GSI screen mounted on the back of the paver what was happening with our concrete." The concrete mix design specified for the project is a very porous, very coarse mix that proved challenging to slipform. Slump averages 1.5 inches. "We have to run the con- crete at a 1.5-inch slump because of the tolerances on the project," Peace said. "We have a one eighth of an inch edge form tolerance. If we don't comply, we have to do removal." Concrete is produced on site by a mobile batch plant set up in the center of the project. The farthest haul the trucks have to make is only six miles. Federal highway regulations limit the weight of the loads the tri-axle trucks are allowed to carry. Up to 18 trucks haul 6.75-cubic-yard loads of con- crete to the paving site. The existing roadway underwent some full-depth patch repairs in areas where the concrete was in poor condition. Then, an overlay bond breaker was applied to correct cross slopes so the new concrete overlay could be applied. The project allows no room for haul roads, so the trucks have to back up to the GOMACO PS-2600 placer/spreader and dump their load directly on the road. The PS-2600, working without the conveyor belt, spreads the concrete in front of the GP-2600 slipform paver. Baskets are placed on grade by hand every 15 feet. The GP-2600 is paving 26 feet wide and 11 inches thick. Hand-finishing work behind the paver is kept to a minimum. "We're running straight edges across it, but we're not rubbing on it," Peace says. "If you have to rub on it, you've got problems that a finisher can't fix in the slab. My phi- losophy is if things aren't going right in front of the paver, there won't be anything right behind it. You have to do your work up front correctly to guarantee a good end product." Two paver-mounted GOMACO GSI units were instrumental in helping Hinkled Contracting fine tune its paving operation. The GSI provided on-the-go feedback of pavement smoothness as Hinkle tweaked various aspects of its paving operation. Concrete paving production averages 2,000 feet per pav- ing shift. Production is limited because of the small loads the trucks are allowed to haul and the Hinkle crew always strives to keep its paver moving at a slow, steady crawl. Also, hand setting both the longitudinal and transverse bas- kets on grade while paving takes additional time and labor for the paving crew. Quality of the concrete is constantly being tested and measured, both with the ride requirement and with core testing. Each 528-foot segment is cored in six different plac- es, with 6-inch diameter cores. Cores are used to test the concrete strength and depth of the concrete, with anything over a 0.25-inch deviation in depth requiring removal and replacement. A GOMACO T/C-600 texture/cure machine follows the paver. The new roadway is transverse tined and sprayed with a white curing compound. "This has been both an interesting and a challenging proj- ect for us," Peace said. "We've paved 528-foot segments with numbers down in the fours and fives on the zero-blanking band. Everybody is liking the ride we're producing." A GOMACO Commander III is slipforming the new concrete shoulders on I-59. One will be 8 feet wide and 8 inches thick. A second shoulder will be 4 feet wide and 6 inches thick. Once shoulders are completed, the new 11-mile northbound stretch of interstate will be opened up to traffic. Then, the southbound lanes of the interstate will be closed so reconstruction can be completed. Better Roads January 2012 35d