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All County Does Justice To Liberty Island Pours

Logistics and LEED [Leadership in Energy and Environmental Design] rating goals dictated use of volumetric mixers for a project involving an addition

Logistics and LEED [Leadership in Energy and Environmental Design] rating goals dictated use of volumetric mixers for a project involving an addition to the Visitors' Center on Liberty Island, home to the Statue of Liberty. Accordingly, John Bernal, Jr., owner of Yonkers, N.Y.-based All County Mobile Concrete, dispatched one of his three Zimmerman Industries 9-yd. Model ZM-409SP Zim-Mixers, producing 30 yards per hour, to deliver 3- to 6-yd. loads on a tight schedule.

To help advance National Park Service LEED rating goals for the project, the volumetric mixer operator implemented a mix design based on high recycled-content materials, i.e., a special blended cement containing 40 percent ground granulated blast furnace slag (GGBFS). The producer enlisted Holcim (US) Inc. to supply the blended cement Û 60 percent Type I, 40 percent GranCem Û in supersacks to ease loading and handling at its yard. Holcim processes GranCem at a Delaware River operation across from downtown Philadelphia.

Moreover, All County's footings and slabs mix had to satisfy a 4,000-psi compressive strength requirement: test cylinders amply exceeded specifications, breaking in seven days at 5,400 psi. Lastly, since Liberty Island comprises merely 12 acres, waste generated from concrete pours and mixer truck washout would have to be minimized. The Zim-Mixer delivered the precise quantity required Û a perfect fit for the Liberty Island project, notes Zimmerman's Robert Byers.

An additional challenge was timely delivery. All County's John Bernal reports that the job has entailed a series of 6:30-9:45 a.m. pours, allowing New York City general contractor F. J. Sciame Construction to conclude work prior to island visitors' 10:00 a.m. arrival. To meet the schedule, All County Mobile has had to ready its truck for 6 a.m. barge boarding at a dock in Jersey City, N.J., about 25 miles from its yard. Work on footings and slabs began in mid-winter and continues this spring. Winter pours required All County to load aggregate, admixtures and water just prior to dispatch; only the blended cement could be preloaded.