EA Tanks and Strata Corporation Awarded for Innovation in Concrete for Their Work on North Dakota’s ZAP Reservoir Project

Owner: Southwest Water Authority - ND State Water Commission
Engineer: Bartlet & West Inc.
Contractor: EA Tanks
Supplier: Strata Corporation
Technology Support: BASF
Technology Support: Midwest Testing Laboratory / Terracon

North Dakota’s ZAP Reservoir project is a 1.6 million gallon water reservoir containing approximately 500 Cy's of concrete. Concrete was chosen for the foundations ring walls and floor because of its structural integrity, durability, and ease of construction. At the client’s request, EA Tanks and Strata Corporation developed an ultra low shrink concrete for Southwest Water Authority’s Zap, ND Reservoir.

When a concrete floor is utilized with our bolted steel tank, it is important to manage the effects that can cause concrete shrinkage. It’s common practice to allow a minimum of 7 days of cure time after placement for the concrete to mature and shrink. The goal was to reduce the effects of the reduction in the volume change that concrete normally experiences as the concrete hydrates. In order to accomplish this goal, a shrinkage reducing admixture (SRA) was incorporated to reduce the internal tension stresses caused by the volume change due to hydration and drying shrinkage.

The design philosophy for the ultra low shrink concrete was to optimize the paste volume and reduce the amount of free water by lowering the water to cement ratio. Structural fibers were incorporated to help reinforce the resistance to this internal tension. In order to create a mix that can be successfully placed, a high range water reducer (HRWR) and a hydration stabilizer needed to be incorporated. Lab trials included shrinkage testing, set times, workability curves, temperature gain, and compressive strength. Lab trial batches of the ultra low shrink mix established the benefits to this approach. A comprehensive placement plan was then developed that included wet curing of the concrete floor slab.

This concrete mix was so successful that EA Tanks repeated the mix design process on their next reservoir project at Wheelock, ND.

Special Thanks to Strata Corporation for working with EA Tanks on this special request!