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Headline: Shape-shifting Sculpture

Tristan Al-Haddad’s Stealth pushes concrete beyond its conventional uses

Stealth looms large in the heart of midtown Atlanta. It is located on 15th Street across from the Woodruff Arts Center on Peachtree Street.
Photo: Rob Felt

Tristan Al-Haddad has transformed a nondescript stretch of concrete jungle in midtown Atlanta with a 33-foot-tall monolithic sculpture.

The award-winning piece, Stealth, is a series of interlocking anamorphic projections that create a folded three-dimensional form. From the perspective of a viewer walking around the work — which comprises a rectangle and an elongated hexagon in projection — it both expands and collapses in space.

Al-Haddad, an assistant professor in Georgia Tech’s School of Architecture, worked on the piece for more than two and a half years and went through more than 200 iterations of 3-D modeling to get the design just right.

While the piece gleams as if it were steel, it is made from concrete.

“We were able to produce highly plastic, very thin forms of concrete,” Al-Haddad said. “When you demonstrate that it can be done in an effective and ubiquitous way, you can start to impact the way in which people imagine concrete can be used. That opens new and exciting design opportunities for everyone.”

A general rule when using concrete is not to go below an inch of thickness. But Stealth goes down to just one-eighth of an inch in some areas, Al-Haddad said.

He worked with Sinclair Construction Group and design engineering firm Uzun & Case to build the sculpture, which was commissioned by Cousins Properties.

The sculpture weighs about 70,000 pounds. The structural framework was built in Al-Haddad’s studio and cast-in-place in front of the Promenade Tower. The concrete was poured in 4-foot vertical increments. Eight tons of steel reinforcing bar were cut by hand, bent, and placed in position.

Al-Haddad worked with chemists from Thomas Concrete Group for two years to develop the concrete mix. It had to have high strength, while still maintaining the ability to flow into the structure’s sharply angled shapes.

Both the coarse and fine aggregate for the concrete were from a blue-black Adairsville granite quarried in North Georgia. The mix included iron oxide and carbon pigments for coloring and synthetic macro fibers for crack control.

After casting, the sculpture was diamond-honed to remove any imperfections, and each section was wet polished to give Stealth a sheer, reflective bluish-black finish.

The real technical impact of Stealth, Al-Haddad said, could be that it eliminates the fear and risk of what others may try in the future.

“This is a demonstration of going beyond the limits of conventional practice,” he said. “When you demonstrate that it can be done, you bring the designers and builders closer together.”

 — Laura Diamond

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