Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.
Issue link: http://concrete.epubxp.com/i/551927
www.concreteproducts.com August 2015 • 35 MIXING & TESTING The concrete and grout schedule at the New NY Bridge operation spans pile, pile and pier cap tub, and pier pours. A sprawling deck of 6,000 precast panels, 40- x 12-ft., will con- sume the largest volume of grout. Work thus far has involved primarily two concrete mixes, notes Dabrowski, both able to be placed above and below the splash zone. "They've been designed to be robust enough to be used nearly anywhere on the job," he says. The large Putzmeister pump moves up to 80 yards per hour of what's described as a "sticky mix," which tests with a one-inch slump before chemicals for work- ability, freeze/thaw, permeability and com- pressive strength are added. "All mixes break at 8,500-10,000 psi due to everything we have in the mix," says Dabrowski, well above the 5,000 to 6,000 psi required. The main mix uses #67 (3/4 in.) stone, with #8 (3/8 in.) stone specified for closure pour mixes such as those between tub and piles. In addition to chilled water in the mix, cooling lines are employed at the pour site to reduce the heat produced by high slag and cement content. Each floating concrete plant has its own lab, housing two quality assurance and two quality control specialists, plus NYS Thruway oversight inspector. Slump measurement, air tests, and cylinder preparation are performed every 50 batches. Plants are certified by the New York State Department of Transporta- tion, which also does annual and random quality audits. Tolerances for concrete are ± 1 percent for cement, and ± 2 percent for aggregates. Altogether, "Several hundred people are involved in QA, QC and random testing," says Mogheera Nagra, a project engineer working for GPI and assigned to the TZC project. "Concrete, rebar, all materials are tested." Dabrowski reports that waste concrete comprises less than 0.5 percent of produc- tion. Forty 6-yd. capacity, ¼-in. poly lined waste pans are used to collect leftover and rejected loads. TZC has two waste barges for hardened concrete, and two waste scows NEW NY BRIDGE IRON, CONCRETE SCHEDULES Equipment needed to build a 3.1-mile bridge: • 48 cranes (35 floating, including Left Coast Lifter/I Lift NY super crane); • Three floating ready mixed plants; • 215,000 yd. of concrete from barge plants; 70,000 yd. from two land-based ready mixed plants; • Over 100 barges, counting maintenance, supply and cranes; • 15 boats, 25-, 36- or 40-ft. for ferrying crews; larger vessels have twin Cat or Cummins diesels; • 7 million gallons of potable water via barge from Haverstraw, N.Y., municipal supply; • Tarrytown, N.Y., field office for about TZC engineering staff and crews; and, • Six Bobcats in sand and rock barges. Raw materials are staged at suppliers' operations, and immediately relayed to the three TZC plant via five supply barges. Suppliers are Tilcon, providing rock from Clinton Point; Roanoke Sand & Gravel, sand from Long Island pit; and, Lafarge North America, cement and Newcem slag cement. Coarse and fine aggregate barges bear enough material for 1,800 yd. of concrete. Barges transfer- ring cement and slag tankers, water and BASF admixtures are loaded for the equivalent of 1,000 yd. requiring excavation. Waste concrete is barged to a yard in Tompkins Cove, 12 miles up the Hudson River. PROJECT STATUS, MILESTONES TZC is about halfway to project completion as of August 2015. A notice to proceed was issued in January 2013; dredging and pile installation began later that year. In 2014, main span substructure and approach sub- structure were started; in 2015, piers are rising and caps are being installed. Main towers will follow, then bridge decks will be installed. By late 2016, traffic will be divert- ed to the westbound span and demolition of the old bridge will begin. In late 2017 the second, eastbound bridge should be complet- ed less than five years from the design-build project's start. Finishing work will continue into 2018, with final physical completion scheduled for April 2018. Lancaster, Pa.-based Ken Stadden specializes in business-to-business marketing communi- cations. He prepared the New NY Bridge report on assignment from BHS-Sonthofen Inc., with assistance from Mixing Division Manager Stuart Bentley. In next month's second and concluding part, he will examine the critical role of Bayshore Concrete Products and Coast- al Precast in TZC Constructors' timely delivery of a Tappan Zee Bridge successor. A follow up report will focus on Unistress Corp. and its record precast deck panel contract. FEATURE NEW NY BRIDGE