Nation’s Largest Science Construction Project Underway
Nation’s Largest Science Construction Project UnderwayContractors for the $1.4 billion Spallation Neutron Source (SNS) project aren’t exaggerating when they say that it is the nation’s largest science project under construction.
Six Department of Energy laboratories collaborated to design the SNS, which started with a vision and 77 acres of vacant land about four miles from the Oak Ridge National Laboratory in Tennessee.
Some 5,500 tons of rebar will be used for the project’s massive structure. The project also calls for pouring approximately 80,000 cubic yards of concrete, equivalent to a three-foot-wide sidewalk that would reach about 400 miles, or the amount of concrete needed to build the Tennessee Valley Authority’s Fort Loudoun Dam. About half of the concrete has been placed to date.
To better understand the magnitude of the project’s purpose, imagine the SNS as a futuristic thrill ride for ions. You start at one end of a very long underground tunnel, about three football fields in length and fire ion beams down a linear accelerator tunnel at very high speeds, accelerating to 90 percent of the speed of light, which is capable of reaching the moon in 1.5 seconds.
Next, you whip the newly formed protons 1,000 times around a gigantic cylinder, then shoot them out the other end at a mercury target where they are blasted to bits, or neutrons. Then it’s off to a liquid hydrogen bath for cool down after which the real endurance test begins – a handoff to scientists for experimentation within the Target Building.
Most people don’t realize how much neutron-scattering research affects our everyday lives. For example, aircraft, credit cards, pocket calculators, compact discs, computer discs, magnetic recording tapes, shatterproof windshields, adjustable seats and satellite weather data all have been improved by this method.
For this massive construction undertaking, a joint venture between Knight Engineering and Jacobs Engineering, as the engineer and construction manager, is taking place. Blaine Construction in Knoxville, Tenn., is the concrete sub-contractor for a substantial portion of the project. Pumpco Inc. of Cleveland, Tenn., is the pumping contractor.
According to Pat Suits, the area manager of Pumpco who is responsible for providing the concrete-placing equipment, “We were selected because of our good working relationship with Blaine Construction. In past jobs, they discovered how effectively our Putzmeister equipment pumps handle the very harsh concrete mixes found in this area – mixes often claimed to be worse than even in Las Vegas.”
For the bulk of the project, the area’s tougher and harsher 4,000-psi concrete at the typical 145-cubic-foot mix, was used. It was selected for various foundations, footings, tunnels, building walls and various slab on-grades. In addition, the job called for other unusual concrete mixes.
A special lightweight mix was used for the elevated slabs in the central lab and office building mezzanine decks. This particular mix featured only 115 pounds per cubic foot of mix, about one-quarter less weight than conventional concrete.
The difficulty with a lightweight mix is that it uses a synthetic aggregate, which is very porous. Therefore, it must soak in water for two days so that it will absorb into the aggregate like a sponge. As a result, it made pumping difficult, as the mix was stiffer because of less water, and it was compressed, having forced the water out of the mix into the aggregate. Yet, modern-day features of today’s pumps have the power and capability to pump it without any problems.
Heavyweight concrete was yet another unusual mix that was used for the Target Building. This material weighs 245 pounds per cubic foot (100 pounds per cubic foot more than normal concrete). Plus, because of its high density, only four yards of concrete could fit on a mixer truck – half the size of a typical load of concrete. In addition, the cost was an astronomical $700 a yard. It was expensive because of the special hematite aggregate, which is an iron ore-type material that takes three months to receive from Brazil. This high-density mix is vital in helping shield against radiation in the Target Building.
Again, Pumpco had their job cut out for them. The heavyweight material was hard to place because it weighs twice as much as conventional concrete and it applies twice the amount of head pressure on the forms. However, experienced Pumpco operators knew how to effectively work the pumps to prevent plug-ups. As a result, the heavyweight concrete was placed successfully without interruption.
Scott Boone, senior project manager of Blaine Construction, said, “The Putzmeister pumps performed flawlessly even when handling the normal, as well as the unusual lightweight and heavyweight mixes. Plus, the Pumpco personnel competently coordinated the dispatching and expertly handled the peculiar pumping and placing requests required for this massive project.”
Overall, Pumpco is handling 99 percent of the pumping with four or five different jobs simultaneously occurring at the job site daily. Everything from a line pump all the way up to the company’s largest 55-meter was used in one aspect or another. Even the Putzmeister Telebelt conveyor was used for convenient placement of backfill – placing rock between equipment foundations and between the walls of the Target Building to keep air out and provide better radiation shielding.
The federal Department of Energy secured the area and required working personnel to wear badges and pass a drug test for admittance to the fenced-in job site. In addition, virtually every day features a different work schedule, a different mix of concrete and a different combination of equipment. This often redefines the need for organization and effective dispatching of pumping equipment.
Scheduled for completion in 2006, SNS will become the world’s leading research facility to study the structure and dynamics of materials using neutrons. It will operate as a user facility that will enable researchers from the United States, as well as more than 2,000 scientists from abroad, to study the science of materials that form the basis for new technologies in telecommunications, manufacturing, transportation, information technology, biotechnology and health.
General contractor: Knight/Jacobs JV, Oak Ridge, Tenn.
Concrete contractor: Blaine Construction, Knoxville, Tenn.
Pumping contractor: Pumpco Inc., Cleveland, Tenn.
Ready-mix supplier: Harrison Ready Mix, a division of APAC,
Oak Ridge, Tenn.
Equipment: Putzmeister line pumps, Putzmeister models up to 55 meters,
and a Putzmeister Telebelt conveyor