New Kid on the Block

iCrete Breaks into NYC Construction Scene in a Big Way

By Debra Wood

New, sustainable concrete concoction is high-strength while using less cement.

It hails from Beverly Hills but is making its biggest splash in the Big Apple.

No, it’s not a washed up screen actor making his debut on Broadway. In fact, “it” is not a person at all. It’s ... concrete?

iCrete, a precisely blended mix of aggregates and cement, has entered the New York construction scene in a big way serving as the foundation for some of the city’s most high-profile jobs, which happen to be calling for high-strength concrete.

“We take the material any ready-mix producer has at its facility, and we look at how we can optimize the mix and put those together in the most efficient manner to achieve the strength and other engineering properties requested,” says Tony Arnold, president and chief operating officer of iCrete, which is based in Beverly Hills, Calif. The mix, he adds, is customized and designed to minimize void space and maximize aggregates, and it contains no additives.

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“With particle-packing, the idea is to put as much stuff in the space as you can,” says Rick Bohan, director of construction and manufacturing technology for the Portland Cement Association in Chicago. “By eliminating microscopic voids, you get higher strength than with conventional concrete.”

Billy Kell, chief estimator for Sorbara Construction of Lynbrook, N.Y., says iCrete is produced in a computer-assisted process that adjusts in real time the amount of ingredients in each batch.

“The mix will have the perfect weight and volume of stone, sand and cement,” Kell says. “You can get higher strength with less cement.”

The iCrete process obtained a patent in the late 1990s. The company subsequently refined it before bringing the product to market last year when it entered the New York construction scene in a big way—snagging placement at the $2.9 billion Freedom Tower project at 1 World Trade Center.

Freedom Tower

The Port Authority of New York and New Jersey specified a high-strength, 14,000-psi concrete in the lower portions of the building, the highest-strength concrete ever used in a New York City building. The previous high had been 12,000 psi. The tower’s below-grade, sheer walls range from 5-ft, 10-in thick to 6-ft, 6-in thick.

California-based iCrete introduced its high-strength, green-friendly formula to New York City in a big way as the mix was used for the foundation of the Freedom Tower project at 1 World Trade Center.

Concrete supplier Quadrozzi Concrete Corp. of Far Rockaway, N.Y., suggested using iCrete. Construction manager Tishman Construction Corp. of New York, structural engineer WSP Cantor Seinuk of New York and Port Authority engineers tested the mix, which contains slag and fly ash, on a 5-ft-thick mock-up at Quadrozzi’s yard, found it met the requirements and agreed to use it.

“The slag and fly ash are industrial waste products that help to lessen the heat,” says Mike Mennella, Tishman executive vice president. He says that with the size of the pours, heat build-up as the concrete cures is a concern. However, iCrete has worked well without the need for an extensive cooling system, Mennella adds.

“So far, we have had excellent results on the heat build-up,” he says. Crews have poured 600 to 700 cu yds per day. “The consistency through the day and the many pours we have to do is important,” Mennella adds.

Looking ahead toward pouring the thickest walls and warmer ambient air temperatures, Mennella says crews may cool the concrete in the truck but not once it’s placed. Tishman has tested pouring at night to compensate for the warmer weather. The team meets before and after every pour to analyze the success of the effort and the result.

Other New York projects

Sorbara has placed iCrete at three high-rise projects. At 11 Times Square, a 1.1-million-sq-ft, 40-story, speculative commercial and retail tower on 42nd Street, the company used iCrete for the 10,000-psi core walls. And at Beekman Tower, a $660 million, 1-million-sq-ft, 75-story, mixed-use, residential tower in Lower Manhattan, it is using iCrete for the 9,000-psi slabs.

In addition to the Freedom Tower, iCrete is also being used on two other high-profile Manhattan jobs: Beekman Tower in Lower Manhattan and 11 Times Square in Midtown.

“It’s absolutely essential, in my opinion, in high-strength concrete in the slabs,” Kell says. “They will get it figured out with lower-strength concrete.”

Sorbara had started placing iCrete at The Harrison, a 22-story, luxury condominium at West 76th and Amsterdam, but switched to conventional concrete after the 10th floor.

“There is still a learning curve with it, and it’s still not up to speed on the flat-work aspect,” Kell says. “We’re not quite there yet on the normal-strength mixes, the 4,000 to 5,000 psis, in the finishing aspect.”

Kell says that with two-day pour cycles, he needs to be able to get on the concrete within two hours after a pour to begin layout and two hours later to start framing for the next pour. But he adds that iCrete is too sensitive and doesn’t allow him to get on the pour fast enough.

“With conventional there is a lot more cement, and it’s more robust,” Kell says. “It could take more of a beating. If iCrete is not tuned up the right way, it can fall apart fast on you.”

With a conventional mix, as the concrete starts to harden, crews put machines on top of the crust. It breaks and the concrete becomes creamy. But after iCrete forms a crust and looks hard, no cream comes to the top. Instead, Kell says it is sponge-like and creates waves. The machine pushes it out in different directions.

At Beekman Tower, the team tried adding an accelerator into the mix to help the interior of the concrete to set up as quickly as the top. Kell says that because of the density, his crews may spread a finishing aid on the floor to finish it.

“We are working and collaborating with him and Quadrozzi to make sure we make the necessary adjustments, so he can get the performance standards he needs,” Arnold says. “Every job is just enough different that you usually have to go back and modify.”

Pouring, finishing and other factors

Crews have poured 600 to 700 cu yards of concrete per day at the Freedom Tower site. The mix is a combination of slag and fly ash, industrial waste products that help lessen the heat build-up, eliminating the need for a cooling system.

“I love it, and think it has a home in the industry, but you have to educate the drivers and mixers differently,” Kell says about iCrete. “You have to work with it differently.”

He says some workers do not want to use iCrete because it is not as hardy and does not allow much room for error.

Arnold counters that it is easier to install because it flows better and requires less labor than with conventional concrete, once crews learn to work with it. Every truck arrives with the same quality mix, he says.

“You also have the reliability that every load is consistent,” Arnold says. “Every truck is not different, which causes delays.”

Kell agrees that iCrete eliminates the need to constantly adjust the mix or add water at the truck.

The foundation for the freedom tower consists of the highest strength concrete ever used in New York City at 14,000psi. The previous high had been 12,000 psi.

Projects seeking LEED certification may turn to iCrete because it reduces the amount of cement in the mix. The Freedom Tower mix contains 42% less cement than conventional concrete, which means less carbon dioxide will be released during its production. Developers of Freedom Tower, 11 Times Square and 76th and Amsterdam are all seeking LEED certification.

“[iCrete] has really caught on [in New York] because that is where there is a lot of interest for green technology, tall structures, high performance and trying to improve the overall consistency of the concrete delivered to that marketplace,” Arnold says. “It [also] happens to be a market where there are a lot of high-rises, and people desire higher-strength materials.”

Useful Sources:

iCrete www.icrete.com