Life Cycle Study Calls for Specialized Concrete Mix in New Jefferson Street Parking Ramp
MARATHON, Wis. (May 20, 2003) - County Materials Corporation was selected to create specialized mixes used in columns and floors for a new six level covered parking structure in downtown Wausau, located on Jefferson Street. The new 350,000 square foot parking arena is replacing a smaller, inadequate ramp unable to accommodate the city's new business growth.
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To establish the criteria for the city's new 650 vehicle parking structure that will perform with minimal maintenance for 100 years, the city of Wausau commissioned a life cycle study. Dave Cook, engineer for the City of Wausau, and Steve Rolof, project manager for Arnold & O'Sheridan Structural Engineers, performed the study under the guidelines of ACI 1365 with Master Builder's software. The study showed that the design mixes needed to be highly impermeable to resist chloride-induced corrosion and prevent the structure from an electro-chemical cell set up.
It was determined that a special concrete mix had to be created for the columns that needed to have a structural strength of 6,000 psi and floors that needed to reach 5,000 psi. According to the specifications, County Materials developed a design mix that employed type I-II cement, flyash, ground granulated blast furnace slag (GGBS), a corrosion inhibitor, high-range water reducer, mid-range water reducer and air entrainment. The mix design needed to meet a low water cement ratio, while providing the concrete contractor with pumpable consolidation. Finishing characteristics and meeting the specified psi within a specific timeframe for both non-post tension and post-tension classifications were also a priority. During the production phase, the mix achieved a 28-day strength of 5,000-6,000 psi.
By having multiple production facilities in central Wisconsin, County Materials was able to quickly access the equipment and expertise required to keep the project on schedule during extremely cold days. "Being a cold winter, there was concern over the ability to produce mass amounts of heated concrete on any given day, and the ability of the concrete to achieve early strength for post tensioning the slabs. We proved that we're more than able to do the job. The post tensioned slabs made the 2000 psi in two days with the specification allowing for seven days," says Bob Wells, manager of County Materials' readymix division. "A combination of the mix design and getting warm concrete through multiple plants was the answer."
In the construction of the ramp, concrete is poured over a pattern of steel rebar and post-tensioned cables. When the concrete reaches 3,000 psi the cables are tightened. The design and construction team included AP Wisconsin, Oscar Boldt, Arnold & O'Sheridan Structural Engineers, Mudrovich Architects and County Materials. Other significant parking ramp projects County Materials has been involved with were for St. Michaels Hospital in Stevens Point and Union Station in Wausau.
For more information on the Jefferson Street Parking Ramp, please call Bob Wells, manager of County Materials' readymix division, at 715-341-0991.
County Materials Corporation has 20 locations throughout Wisconsin and eastern Minnesota and manufactures and supplies a full range of concrete products for commercial building including: prestress, precast, pipe, bridge girders, hollowcore roof and floor systems, concrete block and ready mix. For more information, call 1-800-289-2569.