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Because of the convention center's downtown San Antonio location, concrete boom pumps had to be arranged to allow safe access for the ready-mix truck shown at bottom left.

Because of the convention center's downtown San Antonio location, concrete boom pumps had to be arranged to allow safe access for the ready-mix truck shown at bottom left.

Pumps are Piggybacked in Texas Pour

Pouring 900 cubic yards (688m3) of concrete for a 16,000-square-foot slab at a convention center normally wouldn't be much of a challenge until a couple of obstacles are added to the mix.

First, the Henry B. Gonzales Convention Center is in downtown San Antonio on a heavily traveled street. That, coupled with 100+ degree (38C) temperatures during the day, made it necessary to do the pour between midnight and the morning rush hour.

Secondly, the center is located at the bottom of a hill in an area so tight that the hopper of the Putzmeister 52-Meter boom pump had to rest at the bottom of the incline. The area severely limited access for the ready-mix trucks and the steep grade made it impossible to safely position them at the hopper.

Because the pour was too large to be placed with a tower crane, pumping was the only option. And the only way to get concrete to the 52-Meter at a rate fast enough to keep up with the required 100 cubic yards an hour was with the use of a second pump.

Second pump put at top of hill
This was the solution provided by the pumping contractor, Capital Industries of San Antonio. A second pump, a Putzmeister 36-Meter, was positioned on level ground at the top of the hill.

The tip hose of the 36-Meter was coupled to the deck pipe of the 52Z-Meter with a 5-inch (13cm) sweep elbow. Only the boom of the 52Z-Meter was used, which meant the 36-Meter would have to pump concrete specified at 5,000 psi and a 7-inch (18cm) slump approximately 300 feet (91m) through both units.

"We were concerned if the 36-meter could push 100 cubic yards (77m3) of concrete that distance and how the boom of the 52Z-Meter would react," said Don Faulkner, owner of Capital Industries.

"Both concerns were answered by the end of the pour," he said. "The average output was 135 cubic yards (103m3) an hour, and the 52-Meter boom held steady with little or no surge. Faulkner added that one of the reasons they were able to maintain this rate is due to the "tremendous job done by Alamo Concrete in keeping ready-mix trucks on the pumps."

"Output exceeded my estimates"
Praising the solution suggested by Faulkner, Marty Hanland, project manager for general contractor Clark Construction of Bethesda, Md., said, "I'm very pleased with the two-pump setup. The output exceeded my estimates by 40 yards (31m3) per hour.

"Capital has continued to come through with one successful pour after another," he said. "Each setup has had to be looked at and planned out ahead of time, due to our lack of accessible sites for setting up equipment. This is a very tight area."

The pour was part of Phase II of a renovation of the convention center, which was built as part of the 1968 HemisFair. Today the center is used as a convention facility and exhibition hall and includes an arena for sporting and entertainment events and a theater for the performing arts.

This was just one of several hundred pours done at the center over the last couple of years. It is expected that more than 70,000 cubic yards (53 519m3) of concrete will be used before the entire project is completed.

Job Specs:
Owner: City of San Antonio
Architect: Kell Muñoz Wigodsky, San Antonio
General contractor: Clark Construction, Bethesda, Md.
Pumping contractor: Capital Industries, Inc., San Antonio
Ready mix supplier: Alamo Concrete, San Antonio
Pumps: Putzmeister 52Z-Meter and Putzmeister 36-Meter