Wild Concrete

“The challenge of these exhibits is trying to put realism in them and to make the shapes that we build out of concrete look like different stratas of rock, large standing trees, structural tree trunks, fallen tree branches, carved temple blocks or big boulders,” Cemrock Project Superintendent Larry Hansen explains.

The concrete visible on the temple walls was carved by hand using a variety of hand tools, even specialized ones the carvers developed themselves. “When you apply the texture coat, which is basically a plaster coat, you trowel it up to shape it a bit,” Hansen says. “The coating thickness varies from 2 to 4 in., so you might rearrange it with regular trowels. Then you use a knife or tuck pointer or margin trowel or a specially designed tool to achieve the final design.”

Another decorative concrete feature in the temple is a “tree limb” that looks like it fell through a hole in the roof. There are little pockets in the concrete with bromeliads planted inside them. “These plants don’t take any nutrition from the trees they normally live on,” Kranz explains. “They catch water with their leaves and other animals deposit wastes or die in the pockets, providing them with nutrition.” This means they can live as well on a concrete tree as they would a real one.

The 20,000 sq. ft. of visitor walking paths have integral color made to look like mud. Impressions of leaves, jaguar footprints and white--tailed deer tracks are permanently imbedded in these paths. This decoration has no effect on their longevity. “The load placed on the paths is pedestrian traffic, and the indentations do not markedly reduce the cross sectional area of the slabs,” Wetherell says.

The 6,500--sq.--ft. cafe and 2,600--sq.--ft. restroom building were made of concrete block with the walls decorated using stucco to simulate deteriorating plastered adobe blocks. Because their exterior walls and individual interior spaces are smaller than the temple, using tilt--up would have been more expensive, Wetherell says. These buildings also did not have the heavy concrete facades of the temple, so they did not have to support additional loads.

The 35--ft.--high, 100--ft.--diameter aviary is supported by what appears to be a giant tree. It, too, is concrete, with the tree concealing internal steel support beams. The tree also contains nest boxes and planters, so an irrigation system and service access hide within it. Hansen suggests that the steel pole may not have been necessary. “The tree we built around the column may have been able to support the center of the structure on its own,” he says.

Two jaguar enclosures totaling nearly 10,000 sq. ft. with the capacity for 12 jaguars were made of poured--in--place concrete, hand--carved and theme--painted concrete, masonry and timber framing and scaffold. Through impact--resistant windows inside the cafe, visitors can observe one enclosure, viewing waterfalls, both natural and carved concrete sunning logs, stone ruins with dense foliage and underwater pools. Other exhibit areas house mammals, otters and primates.

Simulated ceramic tile behind the fountains, floor tiles, more than 40 statues, stalactites and stalagmites in the bat enclosure, and “wood” beams over the large windows in the viewing areas were also made of concrete. A cast concrete bench and more than 30 stellas made to look like Mayan stone were fabricated at Cemrock’s Tucson facilities and shipped in by truck.

While working at a public facility like a zoo, contractors need to be aware of their audience. “We’re not your average client,” Kranz points out. “We have a lot of demands and expectations. We’re open to the public all the time and they even enjoy watching the contractors working. It’s a real educational process for contractors who haven’t worked at the zoo to be mindful there’s a public there and how to be around animals.”

The zoo’s expectations for the project were well satisfied. “The contractors cared about this project more than any I’ve ever worked on before, all the way down to the guy with the trowel making the sidewalk,” Kranz says. “I feel like we really received a quality job.”