A beautiful wall appears to be both art and something carved from the earth. It complements a swirling mosaic inspired by the big-bang theory of how the universe began.Chris Coulter, executive director of construction for the school district, and his father, scientist Gary Coulter, came to Colorado Hardscapes to explore how concrete could show molecules, DNA strands, stratified earth layers, and more. After seeing how aggregate, concrete stain, and sandblasting combined with concrete, they developed a plaza design with M+O+A Architectural Partnership and general contractor G.H. Phipps, both in Denver.
The battered wall used layers of concrete to illustrate the history of the earth in sedimentary layers. The wall, 20 inches wide at the base, tapers to 12 inches at the top and is 22x3.5 feet. One truckload of concrete integrally colored with Sequoia Sand by Davis Colors filled the form. In order to create the different layers, placement was stopped nine times. The 3-inch-slump concrete allowed manipulation by workers standing at the top of the form. They reached into the form with trowels to create variegated line and slope the concrete; inserted mosaic pieces along the form boards; spread additional ¾- and ¼-inch river rock, and ¼-inch obsidian aggregate and red granite; then added color hardener to illustrate lines of sediment. Workers stripped the forms early. “A battered wall holds itself up better and earlier than a normal straight wall,” says John Buteyn, senior technical manager with Colorado Hardscapes. Once the form was removed, workers filled the remaining voids and used a water wash to expose aggregates at differing depths. They emphasized the layers with the application of Auburn chemical stain by Bomanite. The work was finished with Okon, a penetrating sealer made by Zinsser.
A slab of brilliant blue concrete, colored with Bomanite's Blue Frost color hardener, is highlighted with Con-Color stain. The color and the float swirl finish creates a water symbol that wraps around the wall. The slab also supports several large natural rocks. “Molecule” clusters were added by cutting stencils, adhering them to the concrete, and sandblasting. The same process was used throughout the plaza to show dinosaur, trilobite, and human footprints. A black paint stain was used to color.
The 2400-square-foot Proto Plaza section is highlighted by a representation of a DNA strand. The V-shapes were sawcut and then colored with topical stain. An angled sandblasted band illustrates the DNA structure and its linear direction across the pattern. The DNA strand is finished with Sandscape Textures surrounding the 5-foot-wide sections of grey concrete. “Sandscape Textures, trademarked by Colorado Hardscapes, is a shallow etch exposed aggregate finish that reveals the sand in the concrete,” says Buteyn. He also notes that the Sandscape Textures finish added a subtle contrast to the plaza's broom swept grey concrete.