Concrete Products

AUG 2015

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.

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Page 34 of 59 August 2015 • 33 FEATURE NEW NY BRIDGE FLOATING PLANT TRIO At the job site based in Tarrytown, N.Y., TZC brought a third floating concrete plant online in June, an Erie Strayer with a BHS twin-shaft mixer. The previous two plants were also equipped with BHS twin-shaft mixers. "Two plants were on the original bid, but we decided three plants would allow us the flexibility to accelerate all aspects of the work," says TZC Lead Engi- neer Wayne Dabrowski. The latest plant's barge measures 54- x 180-ft; the initial two 54- x 150-ft. All three plants can feed 80 yd. of concrete per hour to a Putzmeister 14000 pump serving a placing tower with articulating boom and 5-in. hose. Operators at the new plant benefit from an additional place- ment option: a Putzmeister MXTB600 con- veyor with 110-ft. reach and 150 yd./hour capacity. A small Schwing pump capable of moving 30 to 40 yd./hour is used for grout pours. Typical daily output from the new plant is 200-plus yards. An overview of the Erie Strayer float- ing plant begins with a small excavator chained to one corner, moving rock and sand from adjacent supply barges into hop- pers. Load cells weigh the aggregates, slag cement is added from a 550-bbl onboard silo, and screw augers move cement and fly ash from a robustly braced 300-bbl split silo, built with TZC design input by Shumaker Industries. A 48-in. inclined belt moves aggregates up into a weigh hopper while admixtures enter the hopper through as many as six hoses. Water comes from a 25,000-gal. Pearson water tank, heated and fitted with a Pearson chiller. Though capable of shorter turnaround, the twin-shaft mixer runs 90-second cycles per NYS Thruway requirements, dropping its 6-yd. load into an 18-yd. Maxon Indus- tries remixer, which acts as a buffer to feed the concrete pump's 1/2-yd. hopper. The addition of the placement conveyor enables crews to limit the number of hose swings over the water, an environmental benefit, and increase output. A 480-volt, 800-kW Caterpillar gen- erator and 125-kW backup generator provide electricity; the concrete pump has its own diesel power pack to gener- ate hydraulic pressure. During a pour the barge is anchored by two spuds—posts hydraulically lowered to the riverbed. In addition to supply barges, crane barges are sometimes placed adjacent to the plant for stability. Finally, crew quarters and second-story batch room occupy a central location on the barge. Continued on page 35 TZC has opted for barge-based production for about 75 percent of the concrete and grout to be placed on site as dense residential development on both sides of the Tappan Zee Bridge left no space to permit a temporary plant. Additionally, project principals deemed impractical the movement of mass quantities of concrete to pours along a three-mile wide waterway. Mix production at the placement point augments tight quality control, while reducing delays from rejected loads. Traffc wise, the barge-based plant scheme eliminates upwards of 20,000 loads of ready mixed by conventional delivery. Mixer trucks dispatched from New York and New Jer- sey plants of Eastern Concrete Materials, however, will shoulder about 70,000 yd. for placement at certain site points. TZC added a third plant in mid-2015, orienting the Erie Strayer equipment on a 54- x 180-ft. vessel. The placing tower for the pumped mixes is at the left. The BHS mixer discharges into an 18-yd. Maxon remixer, which serves as a buffer for the Putzmeister 14000 pump. In addition to the pump, the newest plant is equipped with a Putzmeister MXTB600 placement conveyor with 110-ft. reach and 150-yd./hour capacity.

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