Although Standard Concrete Products had considered building a prestress concrete plant in the Mobile, Ala., market before Hurricane Katrina took out the
Although Standard Concrete Products had considered building a prestress concrete plant in the Mobile, Ala., market before Hurricane Katrina took out the 1.2-mile U.S. 90 Biloxi Bay Bridge, the catastrophic storm and resulting destruction helped the company solidify and expedite its planning and site selection process.
With plant locations in Atlanta and Savannah, Ga., and Tampa, Fla., as well as corporate offices in Columbus, Ga., Standard put in bids for Katrina-related repair projects, including the $342 million Biloxi Bay Bridge, long before the Mobile-area facility had broken ground. Katrina hit in August 2005, and by May 2006 we had quoted contractors doing repair work they were about to do, explains Peter Pieterse of Standard Concrete. We were awarded the Biloxi Bay project in June 2006 and began construction on the Mobile plant in August, with production starting in December. The owner had planned on building a plant in this area for some time.
Located a few miles southwest of Mobile, the Theodore operation services projects from the Florida Panhandle to southern Mississippi and southern Louisiana, where it primarily worked on the rehabilitation of New Orleans with U.S. Army Corp of Engineers. The COE studies are ongoing, but something will need to be done to protect New Orleans in the future, and that should involve prestressed concrete, says Pieterse.
REPAIR AND RECONNECT
When it opened at the end of 2006, the Theodore plant’s primary output was pieces for the Biloxi Bay Bridge. At our peak, we were shipping five barge loads of girders per week, says Pieterse.
The bridge work required 43,500 feet of 72-in.-tall _ 120-ft.-long bulb tees and 29,500 feet of 78-in.-tall _ 149-ft.-long bulb tees. All totaled, the plant supplied 561 pieces for Phase 1 and 2 for contractor GC Constructors, a joint venture composed of Massman Construction Co. of Kansas City, Mo.; Kiewit Southern Co. of Peachtree, Ga.; and, Traylor Brothers, Inc., of Evansville, Ind.
All bulb tees were cast using self consolidating concrete (SCC), and the project was a huge leap forward for SCC on DOT work in the Southeast, according to Pieterse. Many DOTs were still researching SCC mixes. For the bridge girders, we used 8,500-psi, 28-day SCC, with 6,500-psi release strength. DOT work is so common at Theodore that a dedicated DOT inspector’s office is located on site.
The design-build structure was erected as a high-rise bridge with 95 feet of high-tide vertical clearance (up from the originally spec’d 85 feet) and includes six traffic lanes and a shared-use, biking and pedestrian path. One lane in each direction opened ahead of schedule in November 2007, an important move in re-establishing a link the cities of Biloxi and Ocean Springs have with Harrison and Jackson counties. The entire Biloxi Bay Bridge rebuild project was completed in May 2008.
Standard Concrete teamed with admixture supplier Sika for the bridge work mix design, which both organizations looked at as a way to promote SCC for DOT work. Sika supplied high- and low-range water reducers, air entrainment admixtures, corrosion inhibitor, and an accelerator. Typically DOTs want trial mixes to reach the 28-day strength, which was [also] the case for this project, says Pieterse. We began our mix trials in October 2006, and by November were done. Construction began at the end of December. The state observed every trial.
PRODUCT AND PROJECTS
Presently, Standard Concrete is occupying 50 of the 70 acres it purchased for its operation. The additional 20 acres is adjacent to the working plant and may be used for future expansion. The site layout leaves room for additional production capacity and storage area over and above the three girder casting and multiple pile beds already producing beams.
Standard Concrete called in Jamieson Equipment Co. and Plant Architects/Plant Outfitters to assist in designing a plant to meet the future needs it would be facing as a Gulf Coast supplier. The environment on the Alabama coast drove a completely galvanized batch plant design, explains Jamieson President Michael Jamieson. New IBC [International Building Code] Hurricane Wind-Loads of 170 mph had to be designed into the batch plant structure and foundations.
The other concern in getting the plant built was time. To expedite the erection and commissioning process, all equipment was delivered via ocean freight to Mobile. The plant’s control room was shipped direct from Italy with the Motor Control Center (MCC) already installed. Skilled Navajo Ironworkers building the plant were coordinated by Jamieson to meet the various loads at the site and unload so that Standard workers would not be distracted from getting the beds ready for their forms.
Due to the nature of the high performance concrete to be supplied out of this plant, a 6-cu.-yd., twin-shaft compulsory mixer was selected. The aggregates for the batch plant are charged by a wheel loader and fed by a 144-ft. _ 30-in. galvanized conveyor to a 326-ton-capacity, four-compartment aggregate bin. From the bin, material is weighed on a belt and then loaded into a skip hoist, which dumps into the mixer, while the cement and water scales are loaded at the same time.
Because of space limitations, a low-profile weigh belt incorporating the custom-designed skip hoist provided the footprint required to fit the property. Other considerations were taken to ensure that the traffic flow of cement, aggregate and admixture deliveries would not interfere with the delivery of concrete to the casting beds. The plant is rated at 210 yd./hour when batching 6-cu.-yd. batches.
To reduce dependency on cement deliveries in the middle of the day and in light of the cement shortage ongoing at the time, Standard elected to go with three 200-ton cement silos. Due to their size, a pre-engineered bolted design was used that allowed the silos to be transported to the site in sea-going containers with the balance of the batch plant equipment. A galvanized understructure common to all three silos was utilized to provide easy access and reduce the foundation requirements. The silos hold Type 2 cement in one and Type 3 in another, while the third is split, storing microsilica and flyash. A dedicated quality control building and staff are located nearby.
An MPAQ Automation package was recommended because of the firm’s history of designing customized systems for precast/prestressed batching plants.
Three Tuckerbilt units with 6-yd. augers discharge concrete to the beds. Standard Concrete Theodore has three twin 400-, 470- and 500-ft. prestressed beam/girder beds, as well as 10 pile beds capable of producing pieces 12 to 24 in. Two ready mixed trucks are also on standby for pile pouring, if the plant is busy. Basically, the trucks are used as back up when we’re pouring a lot in one day, says Pieterse.
The facility is capable of producing square and cylindrical piling; box beams; sheet piles; heavy structural marine and highway elements; plus, slabs and girders, including haunch, bulb tee, and AASHTO-girders.
The beds work in pairs in the same line, rather than side by side. Once the concrete is poured into the forms (supplied by Hamilton Form Co. and Helser Industries), a tarp is rolled out over the line. When the beam or pile reaches release strength, the tarp and forms are removed, and the prestressed strands are cut.
Since the entire production line is open air, the heavy cranes used to take the finished pieces to the site’s dock to be placed on a barge could not simply travel through the yard on unpaved earth. As a result, the yard is criss-crossed with crane paths, which were undercut and stabilized with filler material in paths that range from 36 to 80 inches wide. Due to their weight, if a crane wheel goes off any of the stabilized material, it immediately begins to sink, explains Pieterse.
The plant employs one 70-ton Mi-Jack and two 100-ton Shuttlelift cranes to carry the finished beams to storage and then to a truck or barge for shipping. Depending on the size of the pieces, occasionally two cranes are used for transport.
The 60-ft.-wide dock with 12-ft. draft (the depth of the barge under the water line) was built to purpose for the size barges that are used to take the finished product into the Theodore Industrial Canal. Across the waterway is the Holcim (US) Inc. Theodore cement plant, which supplies Standard Concrete, albeit by truck.
Other major projects Standard Concrete has been involved with since coming online include supplying shipyard piles for shipbuilder Atlantic Marine; producing voided box beams for a loading dock at the Port of Vicksburg, Miss.; and, delivering 1,268 pieces of 16- and 18-in. piles for an expansion project for shipbuilder Northrop Gruman’s Pascagoula, Miss., facility.
The company has also done recent work for the South Shore Marina in New Orleans, two projects for the Barataris Basin Land Bridge in lower Louisiana; a Pensacola fishing pier; and, 20-in. pile and prestressed panels for the Pinto Terminal Slab Handeling Dock Facility in Mobile, Ala.
One notable project about to begin involves producing concrete fender modules for one of the piers of the I-10 bridge over the Mississippi River in Baton Rouge. The modules are approximately 11-ft. deep _ 14-ft. long _ 13-ft. tall, weighing from 54 to 86 tons each. Each module is cast with a number of pockets within, so that if a vessel should impact the pier, the module would collapse protecting the pier. In such as case, only the damanged module would have to be replaced.
Standard Concrete also is currently bidding on some prestressed pile and precast products for the contruction of the Thyssen Krupp Steel mill.
Pieterse says one of the company’s larger and most interesting jobs so far has been supplying about 1,200 prestressed piles and about the same number of prestressed panels for an erosion-control wall in lower Louisiana, designed to protect wetlands for the U.S. Department of Agriculture’s Natural Resources Conservation Service. The piles are driven into the shallow water near the shore line. About two-and-a-half feet remain, projecting out of the water. The piles are driven anywhere from 12 to 19 ft. apart. A 6-in.-thick _ 6-ft.-tall wall panel is then placed between the driven piles that have slots in them to keep the panel in place. Once installed, the wall panels project approximately 2.5 feet above the water line creating a water break which protects the bayou shoreline from erosion, explains Pieterse.