A Win for Low-Carbon Concrete

After years of planning, the construction of the Theodore Roosevelt Presidential Library began in the summer of 2023. Concrete contractor Winn Construction is at the helm using a low-carbon concrete mix to help the building achieve its goal of setting new standards for sustainability. The library is targeted to open July 4, 2026 - the country’s 250^th birthday. Concrete Contractor caught up with the contractor and ready-mix supplier early May 2024 to find out how the work is going and their experience with the low-carbon mix.

The concrete used for the Theodore Roosevelt Presidential Library (TRPL) project is a new low-carbon mix designed to reduce the global warming potential by nearly 50%, compared to standard mixes from the ready-mix supplier, utilizing recycled byproducts such as fly ash and slag. Meant to be a model of self-sufficiency being carbon-neutral, the building was designed to minimize its footprint in both construction as well as environmental. Native plants and seeds were collected along with thousands of yards of soil to be planted on the library’s roof and surrounding areas. Photo by Snøhetta Plomp

Ben Olin, CQTM, assistant ready mix division manager and technical services director of ready-mix concrete supplier Dickinson Ready Mix – sees the library as a generational project for both the company and region as the area doesn’t get that many projects of this magnitude often. “To be able to say that I had a significant role in it – you get the guys in the back talking about it. They love going out there. They love being a part of it. Our team takes a lot of pride in it.”

Photo by Chad ZiemendorfEven though the TRPL is a larger project than average for the area, the team behind Winn Construction were excited to take on the challenge of out their comfort zone. “When we were getting into this over a year ago,” says Winn, “I said to the guys ‘this is going to be a lot of work. Sometimes its easy to go for a shop floor or a building foundation. This is a once-in-a-lifetime thing for us in our area. To be able to work on a presidential library – this is something that doesn’t happen.”

He adds, “It’s a privilege. I’m glad to be working on it myself and most of the people here feel the same way.”

The construction of the Theodore Roosevelt Presidential Library (TRPL) broke ground in July 2023 in the small city of Medora, North Dakota – estimated population 131 (as of 2024). In his online “Message From the CEO,” Edward O’Keefe, Chief Executive Officer for the library foundation, explains why North Dakota was chosen. The story goes that Teddy first came to the area in September 1883 to hunt. Months later, his wife and mother die on the same day. After completing his third term as a New York assemblyman, he returned to the area to mourn and recover. The area and its people must have left quite the impression on him. President Roosevelt was later quoted, “I never would have been President if it has not been for my experiences in North Dakota.” The rest is history.

Medora, North Dakota is also home to the Theodore Roosevelt National Park South Unit. With the history, the location is a fitting home for the new library.

Willie Winn started Winn Construction in 1981 with a single pickup and started on smaller residential and commercial projects. Despite down years, they grew each year – expanding and hiring. “I feel we have a very good group of very hard-working men that really care about what they do and the product that they put out,” says Winn, owner and president of Winn Construction. “I think that’s what separates us from the rest. We have a no quit attitude; a lot of our people are that way,” he says. 

Photo by Chad ZiemendorfWinn started onsite of the TRPL in late July 2023 with the first concrete placement happening early August 2023 and foundations completed May 2024. Winn will be out there all summer with the crew working on retaining walls, civil piers, a maintenance building, and the slab on deck roof. One of the retaining walls placed required a 2.5-ft. thick by 22-ft wide footing incorporating 758 yards of concrete. The retaining walls consisted of 700 yards of concrete.  Each of the concrete-based elements were specified for a different mix design.

Additional features of the TRPL include an auditorium wall designed to be 24-ft. high above grade which will be 12-in. thick around three sides; a stairwell wall, another retaining wall on the other end; and standard footings for the interior foundation.

Familiar with the Doka gang-forming system, Winn contacted a supplier in Bismark, North Dakota for the taller wall sections – but a majority of the project was completed with an Symons forming system.

“A lot of the roof transfer is through the roof into the auditorium walls and then into the structural steel with just pads and piers,” adds Darnell Douglas, vice president of Winn Construction. The company owns their own Putzmeister 47RZ-Meter concrete pump. Rented aerial lifts have also been key for the project with the height of the walls.

Photo by Chad ZiemendorfAs of late April 2024, 4,022 yards of concrete have been placed on the project and the structural foundations. While not breaking world records for the amount of concrete placed, it’s a remarkable project for the area. “This area doesn’t get a lot of big projects,” says Winn. “We don’t get real tall and big walls like this very often…this is a little more than what we’ve done.”

Working a Low-Carbon Mix

Working with the low-carbon mix, Winn says that the low-carbon mix hasn’t affected the construction. According to test results, the concrete was coming back the same or higher than their regular six bag mix they were more familiar with. The mix also included a strength enhancer additive.

Dickinson Ready-Mix contracted Dr. Kevin McDonald, Julie Buffenbarger, and the team at Beton Consulting Engineers LLC out of Minneapolis in the development of the low-carbon mix to meet the sustainability requirements. When they initially started, explains Douglas, one of the problems they had was having such a high replacement factor extending the time that the concrete took for it to reach strength. After working the mix, the low-carbon concrete is able to reach 28-day spec 4,000 psi while reaching 3,500 to 4,000 at seven. “Some of the [concrete] at 28 days, they were getting close to 6,500,” says Douglas. Specifications were performance-based.

Photo by Chad ZiemendorfConcrete mixes utilized a ternary blend of the different cementitious products and strength enhancers – something out of the ordinary for the area. The mix required the optimization for grading, low water, and cementitious ratios to reduce the carbon footprint.

Photo by Chad ZiemendorfThere were seven different mix designs on the TRPL concrete placement dependent on use. “But they all have the same ingredients – all ternary blends of 1L cement,” says Olin.

• Class F fly ash
• Grade 100 slag
• 50-70% replacement rate of SCMs

Winn saw an average of a 4.7% increase costs for the low-carbon mixes:

• Footing: 3.1%
• Retaining wall: 3.7%
• Interior slab on grade: 3.8%
• Shearwall/MD 1: 3.5%
• Shearwall/MD 2: 5.2%
• Exterior concrete 1: 5.9%
• Exterior concrete 2: 7.8%

While the mixes are working, both the Winn and Dickinson Ready Mix teams were aware of the potential issues regarding low-carbon mixes, like potentially needing 56 or 90 days to reach strength. Luckily, this wasn’t the case. “This is definitely a unique mix,” he says. “From my understanding, these mixes are outperforming any expectations. We’re hitting strengths at 28 days,” adds Olin.

Photo by Chad ZiemendorfDouglas confirms; the 56-day break test results were around 6,900. While this is exceeding the spec, it’s a give-and-take situation. He explains that reducing the chemical admixtures to bring strengths down would potentially bring a different problem where lowering overall strength really extends the maturity curve over a period of time.

Because they’ll have a finish to them, Winn and Dickinson conducted a 40 by 40 test panel for the exterior slab mixes. Winn poured and finished it to have a better idea on what to expect and address any concerns.

“For mixes like these, where it’s unique for both the supplier and contractor, it’s essential to have that communication and let them get their hands on so they know what to expect and what’s going to happen in the field,” suggests Olin.

“As people get used to working with it, they’ll adapt to figure out what they need to do,” says Winn. And that’s exactly what happened. Though they were nervous and hesitant with the change from normal, Douglas says that everyone was comfortable with it and happy with they way the concrete was turning out.

“The walls actually look great,” he says. “The finish on the surface is nice. Not a lot of air holes. Our people did a good job because you don’t see pour lines. You don’t see honeycombs and things like that in the surface – they turned out very nice. I don’t think we would have an issue with taking something like this on again.”

The Theodore Roosevelt Presidential Library is expected to open its doors and let all visitors appreciate the brand-new low-carbon concrete on July 4, 2026.

RenderingPhoto by Snøhetta PlompRenderingPhoto by Snøhetta Plomp