With a combination of art, history, and science, the Anchorage Museum creates a rich, deep understanding of the human experience and offers something for everyone. The museum opened its new wing with a traveling exhibit called "Gold," which will dazzle summer visitors with more than 300 gold objects. As part of the expansion, the museum added a dark gray matte concrete floor made of Mapei's Ultratop Natural Gray.

The project consisted of four approximately 10,000-square-foot floors. The architects from Kumin Associates, Anchorage, Alaska, wanted a seamless, perfectly flat, dark gray floor with a matte finish that would not reflect exhibit lighting and distract visitors from the art and artifacts. The specifying architect, Matthias Kunz of David Chipperfield Architects, London, specified Ultratop Natural Gray colored with a darker dye to obtain the desired look.

The substrate was an 8-inch thick post-tensioned slab poured by ALCAN General without expansion or control joints. Mapei and the installer, ARCON, Las Vegas, were challenged with minimizing and hiding pour cold joints, devising a system for sawcutting and grouting cold joints, laying the Ultratop so that the shadow gap was a uniform width, producing a uniform dark gray color, and lightly grinding and buffing the poured surface to produce a matte finish after the sealer was applied.

One of the biggest challenges ARCON faced was finding a pigment that would generate a dark gray color without pigment overload and without affecting the physical and installation properties of the Ultratop. It was also essential that there were no streaks left when installers used a smoothing tool.

Designer's Perspective

The 38,000-square-foot expansion of the Anchorage Museum in Alaska complements the museum's new “Gold” exhibit with dark gray matte floors. The project specified seamless, flat, dark gray floors with a matte finish, in order to minimize any reflection that could distract patrons from the more than 300 gold objects on display. ARCON of Las Vegas used Ultratop Natural Gray—a high-performance, quick-setting, self-leveling concrete topping—throughout the four-floor project.

General contractor ALCAN General, Anchorage, Alaska, started by pouring an 8-inch-thick, post-tensioned slab without expansion or control joints. ARCON minimized and hid cold joints by sawcutting and grouting them. Then the floor topping material was dyed with a darker color to achieve the desired rich gray tones and placed over the substrate. The surface was finished with light grinding and buffing, followed by an application of a floor sealer.