Unusual Mix of Both Concrete and Equipment October 2005
Unique Concrete and Special Placement Approach Fills Piers of Wantagh Parkway Bridge over Sloop Channel
STURTEVANT, Wisconsin (October 10, 2005) - “I've never seen such a unique concrete mix design in all my years working construction,” says Mick Seaver, Modern Continental's project superintendent.
As an experienced construction professional, Seaver was referring to the special mix specified for two major piers during the development of the $68 million Wantagh State Parkway Bridge over Sloop Channel. The New York-based project is under the direction of Modern Continental Construction Co. Inc., headquartered in Cambridge, MA.
The first pier was poured in September 2005, and the unusual mix was supplied by Elm Concrete of Westbury, NY. Since the pour was defined by the state of New York as a 'mass' concrete pour, a special mix was designed and adopted with many attributes of a similar one already used in Florida.
Within its cementitious material, the mix design consists of 25% cement and 75% slag. The uncommonly large percentage of slag (a by-product of processing iron ore to iron and steel in blast furnaces) is rare in mixes; however, its purpose is to slow down the heat of hydration for avoiding cracks. Its special use is in addition to a cooling system of 1/2-inch galvanized pipes within the concrete, which allows water to flow through and keep temperatures low.
The unique mix also included a special retarder, super plasticizers and a host of other additives that resulted in a “one-of-a-kind” mix even before the most significant ingredient - a corrosion inhibitor called CNI - was incorporated. When sixty gallons of the special CNI was added to each eleven-yard ready mix truck that arrived on-site, the concrete almost immediately changed from a two-inch to a nine-inch slump.
Seaver says, “The concrete was placed at 12 foot depths and was so soupy that it took three days to set. In fact, right after concrete placement, we had to erect tents over the 27 foot by 145 foot area, and that proved to be a cumbersome job all by itself.”
Not only was the mix special, so was the array of equipment needed to place it. As no equipment was allowed on the temporary replacement bridge, everything had to be accomplished from barges - even the placement of concrete.
From shore, the specialty concrete mix was discharged into a Putzmeister BSA 14000 trailer-mounted concrete pump - the most powerful available in the market. It pumped concrete through 500 ft. of five-inch delivery line to a Telebelt® model TB 130 truck-mounted belt conveyor, which was strategically situated on a barge. A special A-frame support, built of steel and supported by an angle, was welded together to keep a rubber hose secure while concrete was delivered to the conveyor's hopper.
The main conveyor, in turn, reached over 130 ft. horizontally to place concrete into half of the pier. The other half of the pier was handled simultaneously in the same manner, with a duplicate equipment setup.
Seaver notes, “Because of the unusual mix, we wanted to avoid using as much delivery line as possible to minimize line blockage. Fortunately, the Telebelts® solved the dilemma with their ability to place concrete via their feed and main conveyor belts instead of additional pipeline. This meant we could avoid almost 300 ft. of slick line in total.”
Our Rental Corp. of Farmingdale, NY supplied the two Telebelt® conveyors, which proved ideal companions for the BSA 14000s for this specific application. Covered in plastic on the barges to both keep them clean and clothe them from the salty sea air, they were visibly the final link in the successful placement of the distinct concrete mix.
Nick Avella, Sales Manager at Our Rental Corp. says, “Placing concrete with a Telebelt® significantly reduced the stress level. Because the conveyor can effectively place mixes up to a 12-inch slump, it could easily handle the unusual characteristics of this job's nine-inch slump.”
“The machine's unique versatility gets us in the door of many new customers,” adds Avella, “and it is especially popular when contractors discover they can place so many materials like concrete, sand and stone and yet still reduce labor costs.”
Our Rental Corp. started its concrete pumping services twenty years ago. Today, the company operates a fleet of twelve pumps and three conveyors, used on many prestigious jobs within the surrounding New York area.
“There's nothing better than a Telebelt® for handling a harsh mix on a mass pour,” says Tommy Ruttura, owner of Our Rental Corp. “Modern Continental understood the volume of concrete that had to be placed quickly, and the belt proved to be a very smart way to handle the job. For this major pour like many others, we can send our reliable belts out to the job site without a backup, and without worry.”
The two on-site Putzmeister BSA 14000 trailer-mounted concrete pumps were supplied by Precision Concrete Pumping's fleet located in Albany, NY. They easily gulped down the harsh mix and delivered it a great distance to keep pumping concrete as fast as the ready mix trucks could discharge.
Jason Pino, Operations Manager of Precision says, “Usually, high-pressure BSA 14000 trailer pumps are used in conjunction with separate placing booms for high-rise buildings; however they worked exceptionally well in combination with the Telebelts® to meet the demands for this particular application.”
Seaver says, “The equipment averaged outputs of 150 cubic yards an hour to place a total of 1,550 cubic yards of concrete. All concrete was placed in small one-foot lifts to prevent cold joints, and every detail went according to plan. Because of the pour's success, a mirror image of this placing method will be used for the next major pier later this fall.”
The pour started at 5:00 am and concrete placing was completed by 6:00 pm that evening. With further finishing work and tenting of the area that followed, the entire task took 22 hours from start to finish.
The Wantagh Parkway Bridge over Sloop Channel is 700 ft. long and 150 ft. wide and will feature two traffic lanes in each direction along with a bike path on one side, and walking path on the other. The bridge is estimated to consume about 10,000 total cubic yards of cast-in-place concrete and is projected for completion in late 2006.
SPECS General contractor: Modern Continental Construction Co., Inc. - Cambridge, MA Concrete pumping contractors: Our Rental Corp. - Farmingdale, NY and Precision Concrete Pumping - Albany, NY. Ready mix supplier: Elm Concrete - Westbury, NY Equipment: Putzmeister Telebelt TB 130 telescopic belt conveyors (2) and BSA 14000 trailer-mounted concrete pumps (2)