Georgia DOT Utilizes Smart-Up^® UHPC in Laurens County Bridge Replacement

Recognizing the bridge's importance as a vital link for the local community, GDOT decided to replace the aging structure with a new, wider span built with precast panels and tied together using Smart-Up® Ultra High Performance Concrete (UHPC).

Importance of the Bridge for the Local Community

Robert Taylor explains, “U.S. 80 is a major corridor in East Georgia. Not only is there a lot of freight that comes through here, but there's a large school down to our left, and a lot of people rely on that bridge to get to work.”

Dustin Stokes adds, “It is critical because the county line is that way. This is a major thoroughfare parallel to the interstate. There's a high school on this side, so we're trying to get the road open faster, and that was the intent of using this process.”

Accelerated Bridge Construction (ABC)

The process Stokes refers to is called Accelerated Bridge Construction (ABC). This method uses innovative designs and materials to speed up the construction process for new bridges. One key component is the use of ultra-high performance concrete (UHPC).

In ABC projects, UHPC like Smart-Up® is used to field cast the connections between prefabricated bridge elements. According to the Federal Highway Administration, this approach simplifies connection details and improves the lifespan of the structure.

Overcoming Weather Challenges

The construction team faced significant weather challenges, including high heat, humidity, and even a tropical storm. Robert Taylor observed, “If you look around the site, there’s water everywhere.” Jody Wright added, “Our jobs south of here have been flooded out.” Dustin Stokes noted, “We had some rain from Debby, but we worked around it.”

Taylor described the tough working conditions: “Tropical Storm Debby came in, and if you can imagine, Southeast Georgia a hundred degrees. The humidity’s about the same, so it’s very tough on the guys out here, but they are doing a great job.”

Bridge Construction Details

The new bridge is made up of large precast concrete elements, including deck panels and girders. Jody Wright explained, “The bridge is pretty much a conventional bridge as far as piles, caps, pre-stressed beams, just like any other one we do in the state of Georgia. The panels were new to us. They set on six legs essentially, and we have to grade each one of those out.”

The short lengths of rebar extending from each panel, combined with UHPC, created strong, simple connections between structural elements. To ensure a seamless bond, formwork was set up around the joints, creating molds that held the UHPC in place as it flowed into gaps between panels.

Sealing and Mixing the UHPC

One of the key challenges on the project was sealing the areas that needed to be filled with UHPC. Robert Taylor explained, “We do a water check, ‘cause if it’ll stop water, then it’ll stop the UHPC from flowing out.”

Once the formwork was sealed, the team mixed the UHPC product using a special portable shear mixer. Robert Taylor emphasized the importance of precision, saying, “One of the big things is to make sure you get the right ingredients in the mix. So we brought Jérôme Frécon in from Lyon, France, and he is the head technical guy in France.”

Frécon provided more details: “Basically, what we are doing is using a premix where there is everything inside. It's basically a lot of cement, some fine sand, silica fume or fly ash, and a huge quantity of super plasticizer. Then you put that all together with water in the mixer, mix it for five to six minutes, and then you can add the fibers. The amount of fiber is pretty dense— a lot more than in regular concrete.”

Achieving the Proper Flow

After roughly 45 minutes, the first batch of UHPC was ready to come out of the mixer. Robert Taylor commented, “He can look at it and tell you the exact flow that's going to be measured on the table. He's been making sure that everything is mixed properly, that our mix designs are adjusted for the heat, for the humidity, ‘cause it changes throughout the day.”

The first batch underwent a spread test to ensure the flow range was within specifications. Taylor explained, “This flows so well that we have to use a smaller device. We're looking for about 10 inches because we're having to flow quite a ways where we can't see the product. The specs call for 7 to 10 inches of flow, and we're trying to hit on the upper end of that.”

Placement and Progress

Once the proper flow was confirmed, the Smart-Up® UHPC was loaded onto Georgia buggies and transported onto the bridge deck to begin the closure pour. Jody Wright remarked, “We don't run Georgia buggies; we usually pump concrete, but really that hasn't been a hurdle. Once they got used to it, it’s like second nature to ‘em now.”

Over the next few hours, the crew repeated this process, placing roughly 13.5 cubic yards of material. Dustin Stokes expressed his pride in the team: “I'm very proud of the guys. This being a new process for them, they met the challenge, and I feel like they've done a really good job.”

By the third day of the closure pour, the team had increased their efficiency. Dewayne Doyle observed, “We were about 45 minutes yesterday. We're at about 25 today. So we’re doing good, making better time today.”

Final Stages and Looking Forward

On day three of the project, the team placed approximately 17 cubic yards of Smart-Up®. Dustin Stokes reflected, “First job with UHPC. I think it's an excellent product. I feel like it's gonna be a successful project.”

Jody Wright echoed that sentiment: “It was a hurdle at first, kind of getting used to what was going on. It's a different product altogether compared to normal concrete, and it’s working very well.”

Robert Taylor concluded, “Accelerated bridge construction, UHPC being one of the main components of it, is really catching on around the country and now in the Southeast. As taxpayers start looking at fewer delays, quicker bridge openings, it’s starting to resonate.”