Austin Bridge & Road Co. in Irving, Texas, is currently at work on the I-30 project in Dallas and Tarrant counties.
The project includes replacing the single HOV lane with two new lanes that will be open in each direction. Austin Bridge & Road has its fleet of equipment at work on the project, including its GOMACO three-track Commander III, which is slipforming a variety of different barrier and rail profiles along the 18.26-mile project.
“The largest wall profile on the I-30 project is a single-slope barrier that is 42 in. tall,” Chris Smith, operations manager for Austin Bridge & Road, explained. “It has a base that is 24 in. wide and has a 9-in. top cap. It’s just one of several different profiles of the 213,000 linear feet of wall and rail that we’ll be slipforming on I-30.”
The three-track Commander III with exclusive G+ controls was purchased specifically for the I-30 project.
“We have a GOMACO four-track GT-6300 that we do barrier wall with, but knew we needed to add a machine to help handle the volume of work on this project,” Smith said. “We went with a three-track Commander III because of its mobility and the ease in which we can load and unload it for transport. On this project we may spend a week working in Dallas County, then pick up and load the Commander III for another section of wall in Tarrant County next week. We just drive it onto a lowboy trailer and head out.”
The wall is slipformed over continuous steel reinforcing that has drainage slots on 12-ft centers in the base of the wall. Styrofoam is inserted into the drains to keep concrete out during slipforming and later has to be removed.
Austin Road & Bridge’s wall production is limited to the number of hours they are allowed to work. For example, on days when the Texas Rangers have a baseball game, their working hours are limited to accommodate the heavier traffic load of fans trying to reach the ballpark. Production averages 100 linear feet per hour on the single-slope barrier, with up to 1,500 linear feet per day on larger production days. The concrete for the wall is a standard Texas Department of Transportation mix design with slump averaging between 1.5 and 2 in.
“Monitor the slump of the concrete closely, because if it’s not right by being too wet or too dry, then your wall is not going to be right,” Smith said. “On our projects, the dump man is the most important man on the jobsite, because he monitors the concrete constantly to maintain the perfect slump. If you have a good slump, you’ll have a good wall.”
Very little finishing work is done behind the Commander III, with Smith preferring to let the machine do the finishing work for a nicer finish to the wall.
“We like to keep our finishers back far enough behind the paver so the concrete can set up a bit before they touch it,” he explained. “They can get on the wall too fast and cause mushrooming or other issues. It’s just best to keep them back, let the machine shape the wall because it does a good job with it and let the workers apply the final broom finish and cure.”
Austin Bridge & Road’s work on the I-30 project began last fall and is scheduled for completion in spring 2015. The company specializes in heavy/highway construction and bridge projects in the Dallas-Fort Worth metroplex. R&B