A Walk on the Wild Side November 2006

Florida sidewalk created over an extreme distance with an uncommon trailer pump to trailer pump arrangement and 1,650 ft. of delivery system

STURTEVANT, WI (October 1, 2006) – Pumping concrete for a five-foot wide sidewalk may sound straightforward, but accomplishing it in an environmentally protected area while reaching the farthest point 1,644 ft. away definitely presents a unique challenge.

Going the extreme distance in July 2006 were two powerful Putzmeister Thom-Katt® trailer-mounted concrete pumps from the M&M Concrete Pumping fleet near Fort Lauderdale, Florida. Used in a special pump-to-pump arrangement, the Thom-Katts placed 80 cubic yards of concrete for a long and curving sidewalk through protected wilderness within the 217-acre Yamato Scrub Natural Area in Boca Raton, Florida.

Going the distance

“The job was brutal,” says M&M owner Mike Moberg. “It’s incredibly rare to use two trailer pumps in a pump-to-pump approach, especially when pumping a harsh 3/8-inch pea rock mix such an enormous distance. Plus, we had to be extremely careful not to damage any vegetation while pumping along a looping sidewalk path.”

On a normal pour, a trailer pump from M&M’s twelve-unit fleet uses about 200 ft. of delivery system. At eight times that distance, this job was a highly exceptional and complex endeavor. Still, the demanding mix was capably pumped to a tremendous distance as the result of a strategic combination of high performance pumps, varying delivery line sizes and proper grout priming techniques.

In addition to the exceptionally far distances involved, keeping ready mix trucks from driving over and disrupting the vegetation was key. Therefore, the concrete supplied by Maschmeyer Concrete of Lake Park, Florida was discharged at the scrub’s edge where the first trailer pump, a model year 1998 TK 50 was positioned. With its maximum 950-psi pressure, the unit pumped concrete 700 ft. through two-inch steel pipe and hose to a second pump, which was set up on a narrow access road inaccessible by ready mix trucks.

The second high pressure unit, a bigger TK 70 (model year 2004) featured a turbo-charged 100 hp Deutz diesel engine to pump the mix through larger three-inch line that tapered to a two-and-a-half inch size. It pushed the concrete another incredible 944 ft. of horizontal distance, while snaking around sharp bends before reaching the furthest point of concrete placement 1,644 ft. away.

“To reach such a great distance on this job, we used all delivery system we had available,” claims Moberg. “Therefore, we had a third pump on site as backup, unable to use it any place else.”

Delivery line size is crucial

Delivery line size proved to be a significant aspect of the complex pumping equation. “The smaller the line size, the higher the pressure needed,” notes Jim Henegar, co-owner of Miami-based Thomas Machinery, the Putzmeister equipment dealer in the area. “As higher pressures force water into the rock, the mix tends to dry out and makes pumping more difficult at such far distances.”

“As the concrete would already be stiff from going the long distance from the first pump to the second,” says Henegar, “M&M’s use of a larger line size for the last 944-foot stretch was a key factor in effectively pumping the concrete the final distance.”

“It was quite a challenge, but this approach worked,” Moberg adds. “The larger delivery line size extending from the second pump definitely resulted in less backpressure when reaching the final point of concrete placement almost 1,700 ft. away from the discharging ready mix trucks.”

Protecting the environment

“As the area was environmentally protected, the plants could not be disrupted in any manner,” says Moberg. “We could have avoided about 250 ft. of delivery system if allowed to make a bee-line straight through the scrub.”

To comply with ‘green’ concerns, delivery system had to remain within the curving forms. In addition, crews could only venture 18 inches outside the forms on either side, paying special attention to ensure no foliage was harmed during the construction.

There were also environmental concerns with priming the pump with grout. As a grout primer was a critical aspect, two yards of a high strength 6,500-psi mix were eventually proposed and allowed. To dispose of the primer without placing it within the scrub’s natural habitat or compromising the sidewalk’s integrity, crews put the strong mix as a low one-inch layer within the overall five-inch thick concrete walkway.

Under the direction of concrete contractor West Construction of Lake Worth, Florida, the challenging sidewalk was just one portion of a contracted construction project for various sidewalks, small parking lots and informational kiosks for three different scrubs within Palm Beach County. Ultimately, the company’s construction feats will enable visitors to more conveniently view the natural and exotic plant species along with the protected wildlife of this rare ecosystem.