Originally published in Gomaco World
The I-40/240 interchange in Memphis, TN, currently handles 200,000 vehicles per day and has turned into a congested mess because of continued growth on the east side of the city. And it just keeps getting busier. That number is expected to increase to 350,000 in the next 20 years. On September 20, 2013, the Tennessee Department of Transportation (TDOT) let project number CNM305, the Memphis I-40/240 Interchange, to ease congestion and increase traffic flow on I-240 and I-40 and also the local roads connecting into the interstate system. It is the largest project ever awarded by TDOT.
WMC Contracting Company in Trenton, TN, specializes in several different concrete applications including barrier and parapet wall. When the company learned they would be slipforming over 40,000 feet of four different wall profiles on the Memphis I-40/240 interchange, they knew they wanted to add a new slipform paver to their fleet. The company has always owned GOMACO GT-3600s and Commander IIIs, but for the barrier work, WMC Contracting’s president Dennis Garcia wanted a GOMACO 4400 barrier paver.
“What we really wanted with the 4400 was the capability to pour wall with the direction of traffic,” Garcia explained. “Plus, I like the 4400’s size, the fact that it’s equipped with an auger, and the way it’s built to be a barrier machine.”
The 4400’s 16-inch auger was designed specifically for the low-slump concrete used for barrier applications. It has four-way hydraulic positioning to place the auger perfectly for receiving the concrete and the delivery to the mold which can be placed on either side of the four-track paver.
The operator’s platform has a unique U-shape that puts the operator on top of the action and provides a 360-degree view of the entire paving operation. The control console slides from side-to-side to quickly and easily accommodate right-side and left-side pours.
It’s the company’s first machine to feature GOMACO’s proprietary G+ control system. The tractive system on the 4400 allows for the minimum speed and smooth crawl necessary for a vertical wall. The G+ speed dial turns to adjust in one percent increments and a speed display feedback allows for smooth, precision paving speed control.
Since the 4400 joined the company, it has been at work on the I-40/240 interchange and other projects in the Memphis area. One of the more challenging pours was slipforming the TDOT standard 620-05.01 concrete single slope parapet on the eastbound I-40 flyover. The 4400 and its crew worked on a flyover 108 feet above ground level slipforming the new parapet.
“I’ll admit it was a little nerve wracking to approach the edge of the flyover and look down towards the ground,” Garcia said. “We took extra safety precautions on the project. For example, the guys finishing the outside face of the wall, we only let them work that in two hour shifts so there was no chance for fatigue to set in. We wanted the guys to stay sharp.”
The I-40 eastbound flyover is the fourth level of the interchange. It’s the first of its kind in West Tennessee and stands over Sam Cooper Boulevard, I-240 northbound and the I-240 southbound ramp bridge. The flyover is 2,321-feet long, so WMC Concrete had 4,642 feet of parapet to slipform on the structure.
The single slope parapet is 36 inches tall, with a 7-inch top cap, and 30-inch bottom width. Federal regulations limit the size of the ready-mix loads to 5.5 cubic yards per truck so WMC Contracting, instead of running the normal four truck rotation, increased to between six to eight trucks to keep the 4400 supplied with concrete.
The concrete for the project is a state of Tennessee 3,000 psi Class A slipform mix design with 4% to 6% air content. Concrete slump averages 1.5 inches.
Production on the wall averages 800 feet of parapet and 90 cubic yards of concrete during a six hour day of slipforming. Finishing work is kept to a minimum behind the paver, with a broom finish applied, a clear spray cure, and joints saw cut into the wall at 10-foot intervals.
“The 4400 is performing really well,” Garcia said. “On a project like this, with so many things to coordinate, we haven’t had to worry about our new machine’s performance at all. That 4400 is just so smooth. The smoother a machine operates, the smoother the finish will be on the wall, and you only have to look at the wall to see how nice it is.”
WMC Contracting Company continues to work on the project slipforming their different profiles of wall using the 4400’s right-side and left-side slipforming capability. The entire I-40/240 Interchange has a project completion date of July 2017.
