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Tight Squeeze in Century City
California-based contractor, Largo Concrete, placed the structural concrete for the towers, starting with a two-part mat pour in the summer of 2018.
Boom pumps, line pumps, placing booms perform big work in small space
STURTEVANT, WI (Oct. 29, 2018) – In 2016, Webcor Construction broke ground on the Century Plaza complex in the famous Century City neighborhood of Los Angeles. Featuring two 46-story towers with 300 total condominiums, the construction of two new private residence towers in a compact urban setting presented logistical challenges that were compounded with the presence of a historic hotel — the luxurious Century Plaza. Fortunately, Putzmeister equipment provided crews with the necessary reach and control to keep history preserved.
California-based contractor, Largo Concrete, placed the structural concrete for the towers, starting with a two-part mat pour in the summer of 2018. Among their fleet of pumping equipment on the project was a variety of Putzmeister machines: one 28Z-Meter Truck-Mounted Boom Pump, two 40Z-Meter Truck-Mounted Boom Pumps, two City Pump® CP 2110 HP Truck-Mounted Line Pumps, and six MX 36/40Z Placing Booms with RS 850 Tower Systems.
“We needed a variety of all the different types of systems,” said Largo Concrete Project Executive Mike Daniel.
From a concrete pumping standpoint, the prospect of completing two urban high rises would seem fairly routine — except for the historic structure that’s been on the block for more than 50 years. The Century Plaza, now in the shadow of the towers on the same plot of land, was built in 1966. A landmark in a rapidly developing community, the hotel has been heralded for its advanced technology, its stellar views and its many notable guests including former presidents Ronald Reagan and George Bush.
The First Pour: A Tight Squeeze
The hotel — currently undergoing its own renovation lead by Webcor — is roughly 500 feet (152.4m) long, completely blocking off construction access from the northeast side. Additionally, private property surrounding the site made the maneuver even more challenging. This left Largo with marginal room to work with, in some cases hundreds of feet from the center of the site. Here they encountered yet another nuance: a hexagonal building footprint as opposed to the more common rectangle.
“Everything from the formwork to the climbing system needed to be custom made to fit the hexagonal shape,” said Daniel.
Despite the challenges, Largo was able to secure a reliable ready-mix solution from Catalina Pacific: a CalPortland company, who was prepared to meet the demands of an aggressive pour schedule. The pour would take place over a span of 17 consecutive hours. Beginning on June 9 at 11 p.m., mixers continuously lined up in pairs to feed boom pumps and City Pumps at a steady pace, keeping a consistent flow through the night. Fresh crews arrived on site at 8 a.m. on June 10 to continue an impeccable pour until 4 p.m. that afternoon.
The 28-meter pump, with a horizontal reach of 78 feet (23.8m), and the 40-meter pumps, at 115 feet (35.1m), were chosen for their reach, compact footprint and easy maneuverability. The 40-meter is also “more user-friendly, and its configuration worked best on the job site,” said Largo Operations Manager Ted Bates.
In order to reach the center of the mat, Largo used an assembly of City Pumps connected via pipe systems to the placing booms located on 20–33 foot (6.1–10.1m) sections flanking the mat. Named for its maneuverability in urban settings and high-rise capabilities, the efficient City Pump has a maximum output of 139 cubic yards an hour (106m³/hr). Largo used these machines to deliver concrete through several hundred feet of pipe to the placing booms. In some cases, pipes ran as long as 700 feet (214m).
By the end of the pour, the equipment had placed more than 9,500 cubic yards (7,263m3) for the 155 feet (47m) by 165 feet (50m) mat.
The Second Pour: Practice Makes Perfect
Having completed a challenging first pour, Largo knew what they were up against with phase two, which took place on September 7, 2018. However, the working area here was even more condensed than the first. Located on the southeast side of the block, the second tower is farther from the street on which they had access. This required five placing booms, each connected to a tower system, along with the three truck-mounted boom pumps and two City Pumps.
“On the first pour we had ramp access into the job and we could hit the pour location with long booms direct from street access,” said Daniel. “On the second pour, we had less direct access to the pour and had to pipe in five placing booms.”
A similar approach from the first pour was used as a solution. With another heavy shipment of ready-mix from Catalina Pacific, Largo used pipe systems to move the concrete from the City Pumps and boom pumps to the five placing booms around the mat. Two of the five pipe systems were as long as 600 feet (182m) long, and the remaining three pumped from 450 feet (137m) to the pour site.
“We had quite a bit of line out, and needed to maintain a good push,” Bates said. He added that throughout the 16-hour pour, the pumps were able to maintain pressure for the entire duration, which kept the job on track. Overall, the second pour totaled 9,396 cubic yards (8,592m3).
Once the foundations were poured, Largo put the City Pumps back to work — this time for a higher purpose. As levels were added throughout the construction of both towers, pumps continued to move concrete to the placing systems and up the tower to the placing booms with optimal pressure.
“It has a more reliable push than other [manufacturers’] machines,” Bates said of the City Pump. “It’s a real workhorse.”
Bates noted they wouldn’t have to use the machine at its highest pressure, even at a height of 46 stories. The crew would be able to keep the unit on its low-pressure setting throughout the pour.
According to Daniel, Largo prefers Putzmeister for their equipment’s capability on jobsites that demand the most precision.
“We’re in the process of switching to Putzmeister for its reliability, longevity and maneuverability,” said Daniel.
Crews are continuing to make their way up the second tower. In late October, Largo reached street level and began switching pumps over to PERI systems to complete the pour. When it is all said and done, they will have poured 34,500 cubic yards (10,516m3) in both mat pours and foundations. To date, they have poured more than 30,000 cubic yards (9,144m3). The project is expected to be completed in July of 2020.
The Largo Legacy
Largo Concrete, Inc. is a family-owned company that’s been in the contracting business for more than 25 years. Founded in Tustin, CA, they have since opened offices in northern California, as well as Nevada and Texas. Throughout their history, Largo has completed more than 800 structural concrete projects, including parking structures, high-rise buildings and other industrial, commercial and residential developments.
Owner: Next Century Partner – Los Angeles, California
General Contractor: Webcor Builders – San Francisco, California
Ready-Mix Supplier: Catalina Pacific, a CalPortland Company – California
Concrete Placing Contractor: Largo Concrete, Inc. – Tustin, California
Equipment: Putzmeister City Pump CP 2110, Putzmeister MX 36/40Z-Meter Placing Boom, Putzmeister 40Z-Meter Boom Pump, Putzmeister 28Z-Meter Boom Pump, Putzmeister RS 850 Tower System
The historic Century Plaza Hotel created some job site challenges with access from only one side of the site.
With access from only one side of the job site, crews used a variety of options for connecting to placing systems in order to reach pour locations. In this setup, boom pumps connected to extending pipes to reach placing systems at the core of the pour.
The first of two pours was completed in 17 hours, pouring 9,500 cubic yards (7,263m3) of concrete.
A mixture of boom pumps, city pumps and placing booms were used to access all sides of the job site.
Largo's crews worked day and night on a tight schedule to complete the job.
Adding to the complex job site, the core of the new towers is the shape of a hexagon. Typically, the core of a building is a rectangle.
Mixers lined the perimeter of the west side of the site in pairs for a steady flow of concrete on the Century Plaza pour.