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FEATURE RCC humidity), it is also necessary to further cool the resulting concrete produced. Dry flake ice was the choice of Dragados-USA and Plant Architect's specialty construction division, Concrete Temperature Control (CTC). Dry flake ice was chosen over lique- fied nitrogen due to the remote location of the site and the owner's specification that several days' production materials be kept in inventory onsite. CTC designed and built a large-scale dry flake ice factory producing 150 tons per hour and storing 400 tons of ready-made dry flake ice in a refrigerated enclosure with automated reclaim by live- bottomed floor devices to a pneumatic transfer to insulated ice storage tanks fixed on each of the dual batching plants. DUAL PLANTS, TWIN-SHAFT MIXERS For the multipurpose mixing of grouts, slurries, structural concrete, and of course the large quantities of RCC, Dragados chose to equip the two batching plants with two 6-cu.-yd. output, twin-shaft, high-inten- sity, low-shear batch style mixers from OMG-Sicoma. The mixers received a factory refit with Plant Architects-designed PneuSeal air-type shaft seals patented by Inpro-Seal to avoid undue shaft seal issues. Each mixer provides 150 cu. yd. of concrete per hour, and operates independently of the other. The mixer structures are a Plant Ar- chitects collapsible tubular design, which use no bolts, but rather pins and turnbuckles for fast assembly, all erected on skid bases. Further information on this project can be found at the U.S. Army Corps of Engineers, Jacksonville District website: www.saj.usace.army.mil, and click on the "Portugués Dam, Puerto Rico" link. More information on the design-build offerings of Plant Architects + Plant Outfitters, or CTC con- crete cooling and dry flake ice plants visit can be found at www.robertober.com. Information on Dragados-USA is available at www.grupoacs.com The aggregate cooling facility is shown with one of the three large coarse aggregate cooling/hold- ing tanks to the right, with the chilled recircula- tion pond and water treatment system in the foreground with water chiller towers behind. Be- yond the chillers, note the 1,000-ton cement and fly-ash storage silos for stabilizing the temper- ature of the bulk materials and ensuring a week's production onsite. An aerial view of the concrete production facility shows three coarse aggregate storage tanks at the top of the photo, with the chilled water recircula- tion system above the tanks. The three coarse ag- gregate storage tanks are each fit with two large electromagnetic feeders supplying the 300-ft.- long, dual wet belts, which spray chilled water on the coarse aggregates. Plant Architect's CTC divi- sion designed the coarse aggregate feed system to provide 40°F chilled coarse aggregate. The dewatering and slimes are carried out prior This view of the dual plants under construction shows the chilled sand holding bin, individual weigh hopper system and 200-ton bin with 48-in., high-speed batch belt. WWW.CONCRETEPRODUCTS.COM to depositing the chilled rock in the plant by cus- tomized overhead conveyors. The three higher-pro- file, bolt-together storage tanks hold the cement and fly ash, which is transferred to the plant split silos with an air lock system designed by Plant Ar- chitects. The tanks to the bottom of the photo are the cooled sand storage, while the large rectangular structure to the right of the plant is the 350-ton in- sulated storage and dry flake ice plant customer de- signed by Plant Architect's CTC Division. JULY 2012 | 69