Construction of the new BHP Billiton Tower, a 30-story office building in Houston's uptown district, is destined to be a landmark that will represent the “workplace of the future.” While owners and developers are raising the bar to develop this next generation of premier office space to attract high-quality tenants, Putzmeister concrete placing equipment is raising the structure, literally, with the intricate placement of 35,000 cubic yards (26,760m³) of concrete from the ground up.
The 600,000-square-foot (55,742m²) Class AA office tower is being built to meet LEED® Gold certification and will stand on a 2.42 acre tract in Four Oaks Place—presently a four-building, 1.7 million-square-foot (157,935m²) office complex owned by TIAA-CREF, a financial services firm headquartered in New York City. The tower is 100 percent preleased to BHP Billiton Petroleum, a global energy and resources firm that is a subsidiary of Australian oil giant BHP Billiton Group. Occupancy will occur upon the tower's estimated completion in October 2016.
Construction began in October 2013 with the demolition of an existing health club and the excavation of a new foundation under the direction of Houston-based general contractor, Harvey Builders. The first major concrete task, a continuous 11-hour mat pour, followed in February 2014. It was capably handled by Hi-Tech Concrete Pumping Services, LLC, an ACPA member, with locations in Houston and Kemah, Texas. Established in 2003, the concrete placing company tallies up extensive years of concrete placing experience, with owners Robert and Anna Abatecola at more than 35 years pumping concrete, along with a team of managers, sales personnel and operators, with most of them also at double digit years expertise in placing concrete.
And experience counts when the logistics of the busy uptown Houston location and the job site itself both prove difficult. To accommodate the congested Galleria area and not overextend hours for ready mix drivers, the mat pour occurred on a weekend night. Plus, with limited set up points to access the irregular, five-sided foundation in close proximity to a street, Hi-Tech turned to six larger Putzmeister truck-mounted concrete boom pumps in their fleet—needed for their long boom reaches and high outputs up to 260 cubic yards an hour (200m³/hr). The models included a 63Z-meter, the largest in the Houston area with more than a 200-foot boom reach, two 58-meters, a 52Z-meter and two 46X-meters.
“We always work on the premise that the setup of our placing equipment should never impede the fastest delivery of concrete, so we look at all alternatives to figure out the most efficient setup possible,” says Monty Mullenix, general manager at Hi-Tech with 34 years in the concrete industry. “We don't want to be anyone's excuse that they had to work around us.”
Hi-Tech developed a strategic setup plan with a 46X-meter positioned on level ground at the top of a ramp. Its boom extended about 135 feet (41m) feet to pump concrete directly into the deck pipe of a 52Z-meter, positioned on a specially prepped area in a 30-foot (9m) deep hole. The 52Z had plenty of boom reach, extending its boom out 157' 6" (52m) horizontally to place concrete without additional delivery line. This arrangement meant ready mix trucks would not be forced to negotiate a ramp in and out of the hole and keep the pour progressing at a faster pace.
The other four pumps were located on the only two sides of the excavation available for setup, with the 63Z situated to reach the farthest point about 200 feet (61m) away. A spider web of booms extending into the hole could be seen in the sky, as concrete was placed from a five- to 10-foot (1.5 to 3m) thickness.
After eight-and-a-half hours, pumps began to leave as they finished pumping their area of coverage, starting with the 46X and 52Z combination the first to go. The last unit left the jobsite after 11 hours; and upon its completion, a total 7,700 cubic yards (5,887m³) was successfully placed.
“Each pump averaged 150 cubic yards an hour (115m³/hr), which was not even breathing heavy for the Putzmeister units,” says Mullenix. “Even though the pour didn’t set any records, everything went exactly as planned. “
The lower levels up to the third floor were placed with concrete using different truck-mounted boom pump sizes from Hi-Tech's 26-unit fleet. In July, a Putzmeister BSA 2110 HP-D high pressure trailer pump in combination with a Putzmeister MX 36/40Z separate placing boom took over to handle concrete placement to the top floor.
When installing the placing boom, there were issues about the pipeline going straight up as it would interfere with interior work that needed to be accomplished on certain floors. Mullenix says, “We were able to work with the builder and devise a special route for the pipeline.”
As a result, the pipeline setup involved a zigzag approach with the use of vertical and horizontal runs of five-inch (125mm) pipe while using four thrust blocks. Initially, pipeline would travel up three floors; it would then run vertically across the next floor at a distance of 80 feet (24m) before it traveled upward again to the tower and boom assembly.
“Our 2110 trailer pump has placed concrete up to 50 stories on other jobs, so this high rise at 30 stories should be a walk in the park, even without a straight path for the pipeline,” says Mullenix.
The placing boom, capable of a 115-foot (35m) reach, is mounted on a 70-foot (21m) Putzmeister bolt tower, which was set up in a strategic location, again not to interfere with the anticipated work by the other jobsite contractors. The placing boom, without the need for counterweight, along with the tower are lightweight enough to be raised together by a tower crane from one level to the next, resulting in a fast and efficient lifting process.
The placing boom places about 1,000 cubic yards (765m³) for each floor, inclusive of shear walls and columns. High strength concrete mixes, ranging from 4,000- to 10,000-psi (28 to 69 Mpa), are used. The goal is to finish a floor a week, keeping the pumping company busy meeting deadlines.
Once concrete placement is finished, notable design elements and amenities of the energy-efficient tower will include: a floor-to-ceiling glass curtain wall system, expansive 30-foot (9m) lobby with Class AA materials throughout, stand-alone conference center framed in floor-to-ceiling glass, state-of-the-art fitness facility, functional green roof for meetings and relaxation, and an under-floor air distribution system capable of delivering conditioned air directly to occupied zones.
One of the most distinguishing features of the new tower will be a glass sky bridge connecting to an existing BHP tower. BHP Billiton looked for something more out of the sky bridge than a simple transition. Consequently, the highly specialized design will feature a very spacious width allowing room for tables and chairs where employees can eat and congregate while overlooking an immaculately landscaped park setting. It also includes a dedicated dining area cantilevered out from the structure to be used for more formal occasions.
The premier architecture will enhance the skyline of Houston’s uptown district, which has been mostly unchanged by new office buildings for the last three decades.