At the front end of the job, the widening and reconstruction of U.S. 377 in Keller, Texas, looked like a fairly straightforward project. But when unprecedented rain earlier this year washed out the schedule for the better part of two months, it began to look a bit more challenging.
The $13 million project is expanding U.S. 377 from two lanes to four lanes along a 2.4-mile corridor just north of Fort Worth. The work is divided into four phases to facilitate utility relocation and allow for maintaining traffic throughout the project.
Sunmount Corp., Justin, Texas, began work on Jan. 25, 2007, with 341 working days allotted for completion. While utility and base work proceeded, plans were made for placing the 10-inch-thick concrete pavement. That included trying out a new paver, on loan from Terex Roadbuilding, for part of the Phase 1 paving. The plan was to use the Terex SF3504B only for an extended stretch of the 28-foot 8-inch wide paving.
According to Jeff Nichols, job engineer with Sunmount, much of the rest of the paving work was broken up. For example, more than a mile of the project involved constantly changing paving widths due to driveways, turning lanes, and blockouts. That would require paving a section of one width, skipping ahead to the next section of that same width and paving some more, then backing up the paver and changing its paving width. This time-consuming process would have to be repeated several times in each phase.
Sunmount also was doing the base work on this project, which included treating the base with lime and topping it with a 4-inch layer of asphalt underlayment. Work proceeded through the spring, but as the scheduled start of paving grew closer, the weather turned wet.
“We lost 40 workdays to rain,” says Marty Lampkin, Sunmount's paving superintendent. “It would stop for a day, and begin to dry out, and then it would rain again.”
May and June were essentially lost to rain. The wet weather was so severe and out of the ordinary that the Texas DOT gave a blanket 12-day contract extension to its contractors to at least partially offset project delays. But back on the U.S. 377 project, the paving remained to be done.
Developing a new strategy for the multiwidth paving, Sunmount decided to take advantage of the paver's quick-change paving kit and do all the Phase 1 paving with one machine. Finally, in July, paving began. After paving the widest sections, Lampkin's crew narrowed the paver from a 28-foot 8-inch width to a 26-foot 8-inch width, and in a surprisingly short time even though the machine was new and unfamiliar to them.
“We dropped the kit and walked the tractor away in less than 15 minutes,” Lampkin says. “That would have taken five hours with our other paving kits.”
Part of that speed comes from a unique wedge/pin locking system to connect the kit sections instead of the hundreds of nuts and bolts commonly used. Quick-connect/disconnect hoses for the vibrators also speed the width change operation.
After Lampkin's crew had paved the 26-foot 8-inch sections, they again narrowed the paver to 24 feet, putting a curb insert on each side. With Lampkin on the boom truck, his mechanics completed the change late in the morning. With the paver ready so soon, his crew was able to place another 540 cubic yards of concrete that afternoon.
In addition to direct time savings, the speed with which width changes could be made allowed Sunmount to take advantage of good weather when it was available. In the end, Lampkin says using this paver probably saved them seven days overall, simply based on the reduced time for changing widths.
The DOT specified a new type of optimized, graded concrete for this project. “It's a blend of three coarse aggregates and one fine aggregate,” Nichols says. The idea is to maintain workability while using less water and maintain strength with less cement.
“This is a tough mix to work with,” Lampkin says. “The paver did a great job putting down a good slab.” Early reports indicate there were no must grind areas.
In late September, traffic was transferred to the new lanes of pavement, allowing work on the second phase to proceed in earnest. The project is scheduled for completion by Spring 2009. Although it's still early in the game, it looks like the crew's scheduling flexibility, along with the use of time-saving equipment, might just make that happen.