A consortium of design, construction, and material industry partners came together in late 2023 to evaluate a challenge increasingly shaping the future of concrete construction: how to meaningfully reduce embodied carbon while still meeting the demanding schedules required for modern tilt-up delivery.
The result was a focused field testing program in St. Louis, Missouri centered on experimental low-carbon tilt-wall concrete mixes designed specifically for fast-track applications. The effort ultimately received Honorable Mention in the inaugural TCA Achievement in Sustainability + Resilience Award program.
Led collaboratively by teams from Clayco Construction, Concrete Strategies, Wiss, Janney, Elstner Associates (WJE), Ozinga Concrete, Kienstra Concrete, Amazon Web Services, Breakthrough Energy, and ClimateWorks Consulting, the program sought to evaluate whether lower-carbon concrete mixes could achieve the early strength performance necessary for schedule-driven tilt-wall construction.
Tilt-up construction schedules often require wall panels to be erected within days of placement. Traditional high early-strength concrete mixes are commonly used to support these timelines, with panels sometimes lifted as early as three days after casting. However, many low-carbon concrete strategies rely on supplementary cementitious materials (SCMs), which can alter traditional strength gain curves and raise concerns about schedule compatibility.
To evaluate performance under realistic field conditions, the team produced and monitored three separate tilt-wall panel mixes:
- A control mix using 100% Type IL cement
- A blended mix containing 25% blast furnace slag
- Ozinga’s proprietary Type 1157 blended cement mix
Prior to field placement, laboratory testing conducted by WJE confirmed that all three mixes could achieve the required compressive and flexural strength thresholds necessary for panel erection within three days. Field testing then focused on real-world constructability, placement behavior, finishing characteristics, and early strength development.
According to the project team, all three mixes were successfully pumped, placed, and finished in the field. Two of the three panels achieved sufficient compressive and flexural strength for erection on day three, while the third mix—designed to achieve the greatest embodied carbon reduction—reached strength targets on day seven after colder placement temperatures affected curing conditions.
The embodied carbon reductions achieved through the testing program represented one of the project’s most significant outcomes. Compared to the NRMCA regional benchmark for 5,000 psi concrete, the three mixes achieved progressively lower global warming potential values, with the most aggressive mix reducing embodied carbon by approximately 64 percent relative to the benchmark.
The testing effort also emphasized field practicality. Project narratives submitted as part of the award program noted that contractor feedback during pumping, placement, and finishing was considered essential to evaluating whether the mixes could realistically gain industry adoption. Crews initially encountered workability challenges with the proprietary low-carbon mix, prompting adjustments to vibration and placement techniques that later informed refinements to the mix design itself.
The TCA Achievement in Sustainability + Resilience Award was developed to recognize leadership in the design, construction, and life cycle performance of site-cast tilt-up concrete structures across North America.
While the testing program was not associated with a completed occupied structure or formal certification effort, the participating team emphasized that the work has already influenced subsequent project applications. According to the submission, variants of the tested mixes have since been incorporated into large-scale data center work, with additional testing continuing for slabs-on-ground and future tilt-wall implementation.
More broadly, the effort reflects growing interest across the construction industry in balancing embodied carbon reduction with constructability, durability, cost, and delivery speed—factors that increasingly shape both project outcomes and material innovation within tilt-up construction.
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