Concrete Additive Protects Stormwater Detention Tank

When the city of Oshkosh, Wis., needed to correct flooding issues in its downtown area, conventional stormwater detention systems were deemed unacceptable because of space limitations. Instead, the city opted for a cast-in-place underground solution with precast roof panels.

"For a conventional aboveground basin, we would have needed an entire city block," said city engineer James Rabe. "We looked at the area and realized that we had over two acres of parking lot at City Hall and could do something underneath it."

The plan offered the added bonus of parking facility improvement. The site consisted of two adjacent parking lots formerly under separate ownership. A complete renovation would make the lot much more functional by allowing drivers to maneuver through the entire parking area without having to exit and re-enter.

The concrete producer added XYPEX Admix to the mix design to waterproof and protect the structure as well as improve the concrete's durability.

The site's high water table precluded the use of pre-manufactured stormwater collection devices. Using them would have required redirecting groundwater, which would likely cause settling in surrounding structures. Instead, Oshkosh opted for a cast-in-place detention tank, and the concrete producer added XYPEX Admix to the mix design to waterproof and protect the structure as well as improve the concrete's durability.

Xypex Admix is blended into the concrete mix at the time of batching to help preserve concrete from the start. Further, the Admix C-Series has been specially formulated to meet varying project and temperature conditions. It includes the C-500, which meets concrete practices that incorporate additives such as fly ash and slag; the C-1000, designed for typical Portland cement-rich concrete; and the C-2000 for projects where extended retardation is required.

Xypex Additive products represent one of three different ways to install Xypex Crystalline Technology into concrete. The company's Crystalline Technology is a process that precipitates a chemical reaction between Xypex, moisture and the byproducts of cement hydration, forming a new non-soluble crystalline structure. This fills the capillary tracts, rendering the concrete waterproof.

The design team at Oshkosh also topped the stormwater tank with 249 precast concrete panels from County Materials, a local provider of high-quality concrete construction and landscape products. The decision to use precast minimized the inconvenience of disrupted parking at City Hall, while also helping to significantly lower project costs.

The permanent, non-toxic Xypex Admix allows concrete to breathe, is less costly to apply than other methods, increases flexibility in construction scheduling, is highly resistant to aggressive chemicals, can seal static hairline cracks up to 0.4 mm, resists extreme hydrostatic pressure from either positive or negative surface of the concrete, and ultimately becomes an integral part of the substrate. For ease of use, Xypex Admix is also available in pails, bags or soluble bags.

The project was completed ahead of schedule in the fall of 2013 and promises to be an effective solution to a common urban problem: space. Rabe said, "We're utilizing land we already had without having to go out and acquire more real estate for it."

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