Peculiar Precast

By Mark Crawford

Precast concrete is a vital building material that serves infrastructure needs across projects of all types and sizes. Many of these projects entail straightforward applications using standard components, but some require a creative, artistic flair. These projects often serve as a welcome change as they allow architects, engineers and owners to showcase their creativity while working in tandem with precasters. Three projects that reflect the creative use of precast are presented below.

Life-size farm animals

In 2011, city officials in Thornton, Colo., contacted E&C Precast Concrete to manufacture several low-maintenance, life-size farm animals for a historic local park. After several discussions, the city decided on a draft horse and a pig for Lee Lateral Trail Park and Playground.

Because the project was for a public park frequented by children, the city wanted the animals to be smooth and climbable. Officials also wanted the animals to maintain temperature control. Precast was the perfect material.

According to Kerry McGuire, owner of E&C Precast, precast was selected for its durability, versatility and low maintenance.

E&C Precast realized that the original, 5,000-psi mix design was not as smooth as it had hoped – even after polishing – so Project Manager Chris Wolfe changed the mix design to self-consolidating concrete.

It was a challenging project from the beginning. Wolfe began by trying to find a standard file for making the animals. When that was unsuccessful, he found some small plastic models of a draft horse and traditional farm pig and used them for the final product design. Testing the stability of the first prototype of the horse led to some design modifications, including making the horse’s stance wider and straighter. Wolfe also reinforced the steel frames of the forms.

“Initially, we had decided to pour these animals in two halves, casting on their sides and attaching them on site,” McGuire said. “This would have provided great control for the pour and made them easier to transport. But the customer wanted a heavy, solid and smooth product, so we changed the forming to one solid piece standing straight up, so we did not have to flip them.”

This did, however, make it more difficult to cast the animals and transport them to the job site.

“In most cases, we prefer to use lifting eyes or lifting devices placed appropriately for all products that get this heavy, but for this one we used straps,” McGuire added. “It was definitely a challenging project, but also a lot of fun to do. The animals are a big hit at the park, and we feel fortunate that we could contribute to that.”

Let there be LED light

Armtec, a precast manufacturer headquartered in Concord, Ontario, undertook several municipal projects that involved integrating LED lights with precast concrete for sound barriers. In Hamilton, Ontario, a sound barrier located within a new rail station not only reduces traffic noise created from cars entering and leaving the station, but also provides a secure privacy wall for adjacent residents. In Ottawa, Ontario, the sound barrier surrounds a city bus maintenance facility.

After studying different noise control methods for the Hamilton rail station, the design team selected a double-sided, sound absorptive noise wall. A blend of standard precast concrete panels and Armtec’s Durisol panels compose the noise barrier.

“Durisol precast panels are sound-absorptive composite panels made of a proprietary material consisting of neutralized and mineralized wood shavings mixed and bonded under pressure with portland cement,” said Courtney Goodbrand, technical sales marketer for Armtec.

The panels were installed between galvanized steel flanges and stacked in a tongue-and-groove pattern. LED lights embedded into the barrier create an attractive display across the panels from top to bottom.

Armtec used the same process and materials to build the sound barrier around the perimeter of the bus facility in Ottawa. Not only is the LED lighting aesthetically pleasing, it’s also functional: the moving display of colored lights across the panels represents various bus routes. Different colors represent the routes and the intensity of the LED pulses indicates the frequency of buses on individual routes.

The biggest challenge was manufacturing the panels to incorporate LED box fixtures, conduits and junction boxes. Custom light boxes were fabricated and placed within panel molds. The LED light fixtures were installed and wired on site by electrical contractors. Electrical conduit placed within the panel molds ran vertically from each LED fixture and from the top of the panel to the bottom. Accurate placement was critical for the conduits, which needed to be in the same location on every panel to enable panel-to-panel connections on site.

The tongue-and-groove stacking of the panels, when combined with the LED lighting, results in an attractive basket-weave pattern that creates a sense of movement.

“This is a custom pattern that we helped design with the architect on the Ottawa bus garage project,” Goodbrand said. “With the popularity of this unique look, it has become one of our standard patterns for our noise barrier panels.”

Watching the stars

Building an observation tower is not an everyday task – especially when it’s made from precast concrete.

Wilbert Precast of Spokane, Wash., partnered with Central Washington University in Ellensburg to provide the precast concrete for an observation tower that’s part of the university’s new science building. The tower stands 85 feet tall with an outside diameter of 21 feet. Wilbert Precast teamed up with Structure Engineering to determine how to meet very specific design characteristics. The tower could only sway up to 1/16 of an inch in a 100-mph wind due to a telescope and dome that would be installed on top of the structure.

The project began in the spring of 2015 and finished by early summer. The tower consists of 120-degree-arc precast pieces. Each piece is 2 feet thick, with three pieces making up one level. The pieces include post-tensioned grout tubes and a custom wood grain board and batten formliner in a vertical pattern.

The tower started with a 5-foot, 6-inch tall level with an erection access blockout, which when anchored to the cast-in-place leveling pad created the foundation. Seven full-height levels were manufactured and installed on the foundation.

“All segments had to line up perfectly for the post-tension rods and grout keyways to function,” said Brandy Rinkel, quality assurance and process controls manager for Wilbert Precast. “We ordered a custom metal form as soon as the customer approved the final shape and finish. Without the custom form from Helser Industries, the difficult shape would not have been possible to manufacture.”

Wilbert Precast used an on-site batch plant to mix SCC, which was crucial for the project considering the detail in the formliner and the large amounts of reinforcing required.

“Introducing a formliner with a 3/4-inch deep reveal and then expecting to slide the outside jacket up and out from the product definitely made more challenging,” Rinkel said. “Also, due to the curvature of the form and product, coupled with the texture of the formliner, we had to devise a padded push bolt system to remove the product from the form. A custom wood jig was also fabricated to aid in the tying of double-layered reinforcing cages.”

Capped with a metal dome and a 24-inch-diameter mirror, the observation tower is now a campus highlight. It accommodates up to 25 astronomy students and other stargazers who watch the night skies for planets, stars and celestial events.

Doing it all

Precast concrete will always serve as a reliable, long-lasting option for infrastructure projects around the globe. But it’s also the ideal building material for custom work made possible by the creativity and innovation of architects, engineers and owners.

Mark Crawford is a Madison, Wis.-based freelance writer who specializes in science, technology and manufacturing.