The resulting building façades, which play with available light and shadows, resemble a massive, completed puzzle whose pieces are as distinct from one another as they are equal parts of a larger composition. To achieve the undulating effect Mayne wanted the building exterior to have, the panels had to be uniform in color and composition but different, to varying degrees, in their non-pigmented, striated outer texture.

Gate Precast was able to achieve all the specifications and design intent. After the project was complete, the company was lauded for its work by PCI, earning the institute's design award in the “Best Government and Public Buildings” category as well as a Sidney Freedman Craftsmanship Award, which recognizes “excellence in manufacturing” of precast building components.

Mayne's use of precast concrete also allows the Perot Museum to present a building that is as much a part of the natural landscape as a complementary element of it. The building's design has a sense of movement, lending the museum a part of its desired living quality—if not evoking a sense of time passing. That is, the Perot Museum is less an interruption of the natural, surrounding landscape and more a continuance and development of it, with its planted surfaces and water collection.

Likewise, the museum's mission to educate and inform younger generations about the natural world and their place within it is actually served by the structure itself. Mayne's design presents a number of valuable lessons from the building's aesthetic design to its efficiency-focused construction—a lesson in savings that begins with its precast concrete visage.

From Design to Construction

To benefit the project's coordination and schedule, the concrete subcontractor Gate Precast was called in early to assist with design development and advise on construction approaches. Building information modeling (BIM) would be beneficial to ensuring a faster and more accurate fabrication phase, by using the BIM model for mold shaping and speeding the coordination of panel design and installation.

In Engineering News-Record, Gate Precast's president Dean Gwin said, “We couldn't have done this job without BIM,” with all the related trades “sharing in the 3D modeling.” For its part, the consulting engineer Buro Happold used BIM to simulate engineering elements, integrate design elements, analyze costs, and detect clashes. For the façade work, Gate Precast modeled more than 100,000 square feet of precast cladding in total, which was integrated into the structure's final 3D model.

After the schematics were complete, Morphosis used parametric digital modeling in design development to articulate each individual panel separately using a family of design modules. Developed with the construction team, the Morphosis façade cladding design required about 670 panels in total, each with a unique profile and shape, with each module circumscribed by a 1/8-inch round outline. The modules required a variety of panels, including:

• The plinth. The 27,000-square-foot plinth comprises about 220 panels, including curving, radiused and tilted geometries, which wrap the massive structure. The smallest are about 2 feet by 6 feet, and the largest up to 8 feet wide and 28 feet long.
  
  
• The tower. The cube-shaped, 70,000-square-foot tower set atop the plinth landscape is clad with 350 panels—most 8 feet by 28 feet—with alternating ends sloped at 20 degrees. To make the tower appear more like solid stone, at the corners the panels wrap 90 degrees around and extend at least 4 feet on each side.
  
  
• The atrium. The light-filled lobby atrium, where visitors enter the escalator, has about 100 exterior panels, 10 feet by 10 feet, of which about 90 have a radius—a challenging and unique geometrical puzzle. Adding to the difficulty, a rank of transition panels at the third level appear to be twisted because the top half and bottom half of each panel have opposing curves.

Just as important as the panel forming and profiles to Mayne's aesthetic vision was consistent panel coloration with interesting, nuanced variations. The gray color seems to reflect the natural color of geological features in the Dallas area, suggesting that the building is cut from a rough topological condition. To achieve the desired effect, the architect required a very consistent concrete source, so that the castings would be vary little from panel to panel.

The concrete manufacturers for the job would have to use materials that would produce consistent and uniform characteristics of the final product, according to Descheneaux, Holcim (US) manager, product support. For this key project component, Gates Precast identified a cement plant in Midlothian, Texas, about 30 miles south of Dallas. The source was deemed sufficient to produce this high-quality specification. For the other structural components, the nearby company Lattimore Materials would provide the concrete. The concrete mixes for the project included up to 51 percent of the cement replaced with slag in core walls, and select columns, and 50 percent fly ash in everything else, such as piers, columns and slabs. As an added benefit, the cement plant and concrete suppliers were nearby, which would reduce costs and environmental impact from transportationt.

“It was really driven by LEED. The architect wanted to use fly ash or slag,” says Chris Wolfe, project manager for Balfour Beatty, “in lieu of new material or cement.”