INTERNALLY CURED CONCRETE CASE STUDY: WILSON DAM RENOVATION Material from Arcosa Lightweight is being longer, you get increased strength before [the con- used in extensive bridge deck repairs for crete] starts to desiccate,” Byard says. “The combina- tion of better strength and delayed drying shrinkage Wilson Dam, a 100-year-old hydroelectric gives you a denser, better concrete. The decrease in dam located along the Tennessee River at cracking and increase in mechanical performance are Muscle Shoals, Alabama. Operated by the the values of internal curing.” Tennessee Valley Authority (TVA), renova- tion of the historic landmark is the agen- Renovation Overview cy’s first use of internally cured concrete. Arcosa’s Jeff Speck briefly describes the Wilson Dam project: “The entire project includes some renova- The expert behind the project, TVA’s Ben Byard, is the tions to the dam and to some of the power-gener- agency’s Bridge Program Director and Facilities Asset ating equipment,” he explains. “They also replaced Manager. Byard, who has a PhD from Auburn Univer- the concrete pavement and resurfaced the wall and sity, taught internal curing as a professor and saw the sidewalks. There’s a concrete road that runs across the Wilson Dam project as a golden opportunity to take spillway of the dam which connects two counties in advantage of a key benefit of internal curing: longev- northwestern Alabama.” ity. “Our goal was to provide a 100-year bridge deck and internal curing is a great way to achieve that,” he The roadway atop the dam was constructed between says. 1918 and 1924 and for years, served as a well-traveled and essential route between Colbert and Lauderdale Byard explains other benefits of the process. “Because Counties. Use of the dam to cross the river slowed you keep the internal relative humidity high much once the nearby Patton Island Bridge opened in CASE STUDY: INTERNALLY CURED CONCRETE WILSON DAM RENOVATION 2008, but TVA officials were eager to aggregate with a regional and local Moore says Ready Mix USA has ex- replace pavement on the road dating presence.” tensive experience batching concrete back to the 1950s. with lightweight aggregate, most Local Supplier recently on a major new hospital “The dam originally had brick pavers which opened very near the Wilson as the wearing surface,” Byard ex- Matthew Moore with Cemex’s Ready Dam. But this project was somewhat plains. “In the 1950s, they did an over- Mix USA North Alabama Region says unique. haul of the dam and bridge system. the concrete used in the renovation They pulled up all of the brick pavers project was batched from their near- “We’ve used a lot of lightweight and replaced them with unreinforced by plant at the Florence Industrial aggregate through the years and this concrete decks. To level the concrete Park. “For this job that was our main project was a little different,” says segments, they used a mortar-like facility, which is on the north side of Moore. “Basically, the internally cured material as a leveling agent,” he says. the river,” says Moore. “We also have concrete is designed to a weight and a plant in Tuscumbia on the south to an air spec and like I said, we have But when the driving surface of the side of the river which acted as a to take a little more care with the roadway was being removed in 2019, backup facility.” lightweight and make sure it’s kept extensive damage was revealed. “Be- wet at the plant.” cause the concrete was unreinforced, At the plant, the only special han- cracks formed and increased expo- dling was keeping the stockpile of Like all commercial pours, Ready nentially. Water got in, hit that mortar lightweight material saturated by Mix USA’s quality control team kept layer and caused deterioration and sprinklers. “The material does require a close eye on material batched at settlement. Nasty dips,” Byard says. some additional handling, storage, the plant and delivered to the job keeping it wet,” says Moore. “When site. “We had a dedicated quality When TVA embarked on giving we batch it, we really have to pay control person monitor what we’re the Wilson Dam bridge a modern attention to the moisture content. producing and personnel on site to upgrade, Byard was thrilled. “If I’m While normal weight aggregates only help with contractor communication,” doing a bridge deck, by golly, it’s have about a one percent absorption says Moore. “This project went really going to be internally cured. So, I rate, this material can have over 20%. smooth. The contractor, TVA, the specified that for the concrete. I went It can be difficult with all that water in testing company, I have to say it went to the ready-mix supplier, Ready Mix the lightweight, so we have to watch well. The things that I thought would USA, and they suggested Arcosa. I how it impacts the mix.” be issues, we just didn’t have them.” really wanted to use a lightweight CASE STUDY: INTERNALLY CURED CONCRETE WILSON DAM RENOVATION Specifying Internal Curing help reduce cracking in the pavement seat of the TVA when it was formed helping it to last longer. We’ve been back in 1933. He says helping restore Speck and Arcosa Sales Rep David promoting internal curing for a long the only neoclassical-style dam built Annestedt were more than happy to time now,” Speck says. by the U.S. Army Corp of Engineers help Byard with the project’s light- in the TVA system has been the weight needs. If you’re new to Arcosa “The industry spent a lot of money highlight of his career. “It’s a big deal Lightweight’s product, Speck de- and time on research of internal cur- because Wilson Dam is on the Nation- scribes the material Byard specified. ing and the benefits that it provides to al Historic Register and it’s a National the service life of concrete structures. Historic Landmark as well,” he says. “It’s lightweight fine aggregate, which Actually, Ben was involved in some is like sand, that’s been pre-soaked internal curing research when he was Renovation of such a landmark is not before batching the concrete,” Speck getting his PhD at Auburn.” a quick process. For one, all poten- explains. “It replaces just a portion of tial changes and updates had to be the concrete sand. There’s probably Byard says his research was funded approved by the Department of the 250 pounds or so of the lightweight by the Expanded Shale, Clay, and Interior because Wilson Dam is part of aggregate in a yard of concrete, and Slate Institute (ESCSI). “It was on the U.S. National Park system. Byard that relatively small replacement of lightweight concrete in bridge decks,” says it was worth it. “It’s still a really concrete sand with pre-wet light- Byard says. It’s during the course of loved, relevant structure.” weight aggregate provides internal his advanced studies that Byard first moisture to keep the hydration crossed paths with Speck. When asked if he would use Arcosa process going longer as the concrete Lightweight again Byard says: “In cures.” A Special Landmark a heartbeat. For a relatively minor increase in cost, you get a lot more He reinforces Byard’s assertion on The region of Muscle Shoals is special bang for your buck in the perfor- internal curing’s value saying, “It re- to Byard and the team because, as mance.” duces early age shrinkage, which will he points out, the area is the original In 1918, by the directive of the U.S. War Depart- ment, the Army Corps of Engineers began con- struction on Wilson Dam, a large hydroelectric project that was to supply power to U.S. Nitrate Plant No. 2 in Muscle Shoals, Alabama. (Library of Congress).