Internally Cured Concrete Enhances Water Tank Durability in Denver Water Projects
Key Insights:
Quick Facts:
- Name: Water Tank Replacements
- Location: Lone Tree, Colorado
- Customer: Holcim US
- Client: Denver Water
- Size: 1,300 CY of ICC used for floor slabs, 1,800 CY for roof slabs
Challenge: Placing large concrete slabs for water storage tanks without construction joints in a low-humidity and windy climate presented challenges related to shrinkage cracking and durability.
How Arcosa Helped
- Our Solution: Arcosa provided prewetted expanded shale lightweight aggregates in collaboration with Aggregate Industries (Holcim US) to create an Internally Cured Concrete (ICC) mixture that reduced shrinkage cracking and improved durability.
- Why Lightweight Works: The prewetted lightweight aggregates helped achieve the desired strength, placing, and finishing properties for the slabs, walls, and columns, ensuring long-term durability and reducing shrinkage cracking.
Final Results
- ICC was successfully used in the renovation of the Lone Tree Tank No. 2, reducing shrinkage cracking and accelerating the construction timeline.
Key Quote
“Internally Cured Concrete is a great way to improve the quality, performance, and long-term durability of large-scale treated water tanks.” – Erik Holck, P.E., Former Denver Water Engineer
Context:
- Considerations: Low-shrinkage concrete and ICC proved to be the best methods for combating the challenges of Colorado’s climate, ensuring better curing and enhanced structural durability.
- Lesson to Learn: Using ICC and prewetted lightweight aggregates significantly enhances durability and helps reduce shrinkage cracking, especially in challenging environments like Colorado.
Explore Further
Learn more about how Arcosa Lightweight aggregates can help address complex construction challenges in large infrastructure projects.
Internally Cured Concrete Enhances Water Tank Durability in Denver Water Projects
Denver Water is committed to ensuring safe and reliable water for its customers. To achieve this, the utility continually upgrades its system by replacing aging, large-capacity water storage tanks with more durable designs that are less susceptible to leaks. One way they have done that is through the use of Internally Cured Concrete (ICC).
This material has been successfully employed in multiple major tank replacement projects, including the Lone Tree, Highlands, and Ashland facilities, where it has helped to significantly reduce cracking and improve long-term performance.
At Lone Tree, a new 10-million-gallon underground water tank was constructed, providing a reliable water supply for the Southgate Water District and meeting fire response needs. In Highlands, Denver Water built a 7-million-gallon circular post-tensioned concrete water storage tank. At Ashland, two 20-million-gallon tanks were replaced as part of a major upgrade.
Why Internally Cured Concrete Works
Internally Cured Concrete has been crucial to the success of these projects by reducing shrinkage cracking and enhancing durability.
ICC uses expanded shale, clay, or slate (ESCS) lightweight aggregates, which absorb and gradually release water to sustain hydration throughout the concrete. This ensures a more uniform cure, preventing early-age shrinkage and cracking.
Bill Wolfe, Marketing & Technical Manager for Arcosa Lightweight, explains: “Internally cured concrete acts just like ordinary concrete, but with the additional benefit of reduced cracking and leakage. Once we demonstrated its effectiveness, Denver Water saw the results firsthand, and made it standard practice to use ICC in many of their tank replacement projects.”
Addressing Slab Placement Challenges
Placing large concrete slabs without joints is a challenge, especially in Colorado’s dry and windy climate. Erik Holck, P.E., Semi-Retired Civil Engineering Consultant, who spent 24 years at Denver Water, notes, “We constantly looked to improve the durability of our facilities, and Internally Cured Concrete was a great way to improve the quality, performance, and long-term durability of our large-scale treated water tanks.”
For the Lone Tree Tank No. 2 project, Holck and Robert Bates of Bates Engineering chose an ICC mixture to ensure both the base and roof slabs could withstand the harsh climate without succumbing to shrinkage cracking.
Lightweight Aggregate Utilized
To meet the specific project requirements, Aggregate Industries, now part of Holcim US, produced the high-performance ICC using prewetted expanded shale lightweight aggregates sourced from Arcosa’s Boulder, Colorado, operation. The aggregates helped achieve the desired strength, placing, and finishing characteristics for the slabs, walls, and columns.
According to Wolfe,
Broader Infrastructure Upgrades
Denver Water manages 31 treated water storage tanks across its service area. Since adopting ICC, eight of these tanks have undergone major upgrades, significantly reducing shrinkage cracking and enhancing durability. These upgrades are part of Denver Water’s broader initiative to improve infrastructure and deliver safe, reliable water to over 1.5 million people in the Denver metro area.
Internally Cured Concrete has proven to be a highly effective solution for reducing shrinkage cracking, improving durability, and streamlining construction schedules. As Holck explains,
With successes in projects like Lone Tree, Highlands, and Ashland, Denver Water plans to continue utilizing ICC across future tank projects to ensure long-term performance and reliability for its critical water infrastructure.
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