It took the world's largest boom pump for the expansive bridge pour.

Located 10 miles from downtown Atlanta, Hartsfield-Jackson Atlanta International Airport is considered to be the world's busiest airport, handling more than 80 million travelers and 700,000 tons of cargo each year. In 2000, the City of Atlanta initiated a 10-year, $5.4 billion "Hartsfield Development Program" to enable the airport to meet future demands, predicted to be 121 million passengers by 2015.

As the largest public works project in the history of Georgia, the overall expansion encompasses six massive construction projects. The centerpiece of the colossal expansion is the fifth runway addition (Runway 10-28), slated to cut flight delays in half.

Construction solely for the runway has also been broken down into six key projects. This includes site preparation, which required moving 18.5 million cubic yards of earth (enough to fill the Georgia Dome six times over) and filling embankments up to heights of an 11-story building. Other projects include the relocation of power lines and a new substation, two major road relocations, construction of an Interstate 285 bridge structure and a new FAA control tower.

When completed, the fifth runway will be 9,000 feet long with a full-length parallel taxiway and dual north-south taxiways, which connect to the existing airfield. The unrestricted air carrier runway will be able to accommodate CAT III operations (take-offs and landings in all weather conditions).

The new runway will cross over 10 traffic lanes of Interstate 285, with two-thirds of the runway pavement on the west side and the remainder across the road on the east. Linking the two sections is a massive $159.5 million bridge, which will allow planes to literally take off and land atop the busy road. The bridge is expected to withstand a load of around 600 tons, which is more than the weight of a 1.04 million- pound wide-bodied Boeing 747 or 1.33 million-pound Airbus A380.

Although the highly unique bridge configuration will span 10 traffic lanes, it still allows for eventual expansion of up to 18 lanes. At an impressive size, the main runway bridge measures 1,200 feet long and 486 feet wide, and its taxiway bridge is 450 feet long and 450 feet wide. The bridge is so vast that the support structure will create a tunnel, although none of it is underground.

On a fast track

To meet unique engineering demands and coping with the time constraints for a May 2006 runway completion, Archer Western Contractors Ltd of Atlanta, leads the design-build team for the bridge structure. Bovis Lend Lease is the senior company of a joint-venture team (Hartsfield-Jackson Construction Management), managing overall construction of the approximate $2.1 billion runway.

Several "firsts" are related to the new runway. As one of the most complex structures of its kind in the world, it is the first design-build project of this size and complexity in the state of Georgia. It is also the first roadway tunnel in Georgia as defined by NFPA 502 (an internationally recognized standard, which covers the entire spectrum of what one would see in terms of fire safety within road tunnels), and it's the first runway bridge of this span length in the world.

In addition, it is the first time the Putzmeister BSF 63Z-Meter, the world's largest concrete boom pump, was brought on site to accommodate a special placement of concrete. The unit was supplied by Pioneer Concrete Pumping of Smyrna, Ga., which took delivery of North America's first BSF 63Z-Meter model early in the summer. As one of the largest firms in the country engaged in the business of concrete pumping for commercial, highway, industrial and residential construction projects, Pioneer has been a leading force in concrete pumping since 1973.

The project will feature 764 "T-shaped" pre-cast concrete beams with a total length of 90,000 feet. The beams are 81 inches tall and vary in length from 94 feet to 133 feet for both the runway and taxiway bridges.
The combined bridge decks total 725,000 square feet and will contain approximately 37,000 cubic yards of concrete. The bridge structure consists of 430,000 square feet of cast-in-place and pre-cast walls. The runway's interior substructure features solid concrete walls measuring 3.25 feet in thickness and varying in height from 35 feet to 60 feet.

To construct the bridge, slabs skewed at a 45-degree angle are being pumped with concrete at the rate of about two 20,000-square-foot slabs a week. A Putzmeister BSF 52Z-Meter has performed the lion's share of the work with experienced Pioneer operator Herman White at the controls.

Close to the edge

Typically, the boom pump could set up in the middle of the progressing runway and extend its boom 170 feet vertically and 158 feet horizontally for full concrete coverage. However, when reaching the end of the runway, a different setup location requiring greater reach was needed to access the entire pour. The BSF 63Z-Meter with more than 200 feet of vertical reach and 190 feet of horizontal reach easily handled the task.

Pioneer's 25-year veteran boom pump operator, Bob Shillinger set up the BSF 63Z less than 36 inches from the edge of the runway.

"I wasn't the least bit worried about setting up this larger boom pump, because if the bridge's runway can withstand a counterweighted Manitowoc 999 crane or a million-pound 747 landing at a 30-degree angle, it can easily accommodate any of our equipment without a problem," Shillinger said.

Shillinger skillfully operated the boom pump for full concrete coverage within the approximate 120-foot by 200-foot area. With the benefit of the 63Z's Ergonic control system in hand, he had the ability to set pump parameters as well as view and change functions from an LCD screen in the modular control box. The unit's ergonic output control helped ensure optimum engine RPM for low-fuel consumption along with reduced wear and noise levels. Finally, its boom control with OneTouch meant a single joystick could move all boom sections and slewing in tandem while keeping the end hose level.

"Overall, the entire concreting process went smoothly, and the equipment earned its keep that day due to its longer reach and reliable performance," he said.

Working both units

Pat Inglese, owner of Pioneer Concrete Pumping, said both the BSF 63Z-Meter and BSF 52Z-Meter concrete boom pumps were needed at the new runway for an early 5 a.m. start on a hot Saturday in July. Their job was to effectively pump a 540-cubic-yard slab to an 18-inch depth.

The BSF 52Z-Meter, operated by White, was required to take care of a smaller concrete placing area for faster overall job completion that day.
It was an ideal job setting to show off the benefits of both Putzmeister units.

As the world's largest boom pump, the BSF 63Z demonstrated its maximum horizontal reach, which was fully extended for complete coverage of the area without running additional hose. Although both the BSF 63Z and the BSF 52Z boast a five-section Multi-Z boom configuration, the BSF 52Z was able to better show off its boom versatility in this application. With its dictated spot of setup below the bridge, it first extended its first two boom sections vertically, which left three remaining booms to extend horizontally over the bridge for more effective reach.

"You can't accomplish that type of versatile reach with a big boom that only has four boom sections," Inglese said.

Alkali-silica reaction

In addition to the efficiency of pumping concrete, the concrete mix itself was a highly critical ingredient in the success of the project. Because alkali-silica reaction or ASR can cause premature deterioration of concrete, advanced lithium technology is being used to combat ASR.

Evidence indicates that lithium forms an alkali-silica gel that is non-expansive. Lithium silicates are less water-soluble and do not absorb or bind water to the degree that sodium or potassium silicates do. While the reaction of lithium with the ASR reaction product appears irreversible, there should be sufficient lithium present in the pore solution to protect against future attack by any alkalis remaining in the concrete structure.

While lithium compounds have been recognized for more than 50 years as being effective in preventing concrete expansion due to ASR, only limited field applications have resulted. This means inadequate "long-term" research and lacking guidelines are available. However, the Strategic Highway Research Program places lithium compounds on the "short list" of recommended preventatives and remedies for ASR.

Therefore, using what is believed to be best available technology today, the use of lithium was further investigated to arrive at a calculated ratio to ensure the best structural viability.

The resulting dose rate was 770 ounces per 9-yard load of concrete, with the concrete supplied by the Atlanta branch of Cemex.

Shillinger said that frequently Atlanta mixes - with their manufactured sand - can be downright nasty; however, this 5,000-psi mix was entirely different.

"This particular concrete was a good rich pumpable mix with a 4-inch slump, much better than most I've pumped," Shillinger said.

Although each boom pump is capable of more than 200 cubic yard outputs per hour, the overall pour took approximately 6.5 hours due to stressful concrete delivery demands and hectic Atlanta traffic.

Safety concerns

With a project of this magnitude, safety is also paramount. In addition to training in safety procedures by Pioneer and certified to the pumping industry's standards, an equipment operator destined for the jobsite must also attend a four-hour safety class presented by the airport's insurance company.

The class outlines various safety techniques and stresses the importance of wearing appropriate safety gear, including fluorescent vests. It also covers special concerns related to airports. For instance, workers must refrain from bringing plastic water containers, which could be blown around the tarmac; and no food is allowed onsite to prevent birds from flocking to the area and getting sucked into a plane's engine.

Upon completion of the airport safety class and having passed a security clearance check, a badge grants admittance to the site. As Pioneer has been at the airport for several other jobs associated with the overall expansion, almost all their operators have badges.

As the Southeastern portion of the United States continues to grow both in terms of population and economic development, the goal is to ensure that Hartsfield-Jackson maintains its global leadership role. Now in its fifth year, the airport expansion program marks a productive halfway point in a major endeavor.