Designers at Cambridge Seven Associates Inc. considered other cladding systems, such as metal panels and glass, for the 10 story, 410,000 square-foot Hilton Hotel at Boston's Logan Airport. But they realized that precast concrete architectural panels would provide the best solution. The system not only created a pleasing look but added acoustical control that dampened noise from nearby jets.

Airport officials, who also manage the hotel, wanted a building with a modern expression but with a different look from neighboring buildings, according to Gary Johnson, principal in charge of the design for the Cambridge, Mass. based architectural firm. "We decided on precast concrete mainly because of its cost-effectiveness and ability to buffer the sound of planes and vehicular traffic." But aesthetics also were important, he adds. "A major advantage to using precast was the variety of façade concepts that were possible. Panels can be virtually any color, texture, shape and size."

TEXTURES, REVEALS DOMINATE
The architects designed a façade with an arresting pattern, using texture, color, variations in finish and deep reveals. The panel system was designed to reflect the module of the hotel rooms and the building's structural system. Two 9'-4'' by 26 foot panels cover four guestrooms. Casting diagonal ribs on portions of each panel face created texture.

Bétons Préfabriqués Du Lac Inc. (BPDL), the architectural precaster, used a four step process to create the panels' bush-hammered ribbed pattern. First, they made a wood mold detailing the ribs. Then a master mold was made in concrete with an exposed aggregate, for which only selected round pieces were used to achieve the bush-hammered effect. Onto this mold were poured polyurethane mats, which were ready to receive the colored concrete. Separated by reveals, ribbed sections are combined with smooth areas, and the whole panel finally received an acid-etched finish. The project required 50 different polyurethane mats.

The panels were cast in two integral colors, as well as two finishes. A brick-red color is the building's dominant color accented by a buff tone. Due to the angles at which the sun hits the building, it often appears as though there is a third color. "This was our first use of this pattern in a large application, so we conducted a number of studies examining how the sun struck the building during different times of the day," Johnson says.

The panels were alternated during installation, with the diagonal direction of the ribs and the colors varying from panel to panel in relationship to the fenestration and other architectural elements. As a result, sunlight moving across the façade creates rich and varied patterns throughout the day.

Additionally, most of Logan Airport is built on fill, so 14-inch prestressed piling was used to stabilize the foundation. Northeast Concrete Products LCC of Plainville, Mass. supplied approximately 16 miles of spliced piles, each with a capacity of 130 tons.

The architects designed an eye-arresting pattern for the architectural precast on the Hilton Hotel at Boston's Logan International Airport. They selected precast for its noise protection and cost-effectiveness, as well as for its aesthetic qualities.

PANELS DAMPEN NOISE
The 8-inch thick precast panels serve as an excellent noise buffer. Formed to accept aluminum window frames, the panels embrace the frames and were caulked on both the inside and outside for better noise protection. The architects specified a specially colored caulk to match the precast panels, which keeps the sealant invisible, helping conceal the joints between panels. This allowed the patter of deep reveals to stand out.

The precaster produced 20 samples and a full-scale mockup of four full panels, measuring 52 by 18 feet. "We took our client up to Canada to see the mock-up, and they approved it right away," Johnson says. "The precaster did a terrific job in quality control." The hotel was clad in approximately 764 panels covering a total of 134,000 square feet.

The panels were erected efficiently, saving time and money when compared to other façade treatments. Located in the middle of the airport complex where new roads were under construction, the hotel's site was extremely tight. To prevent traffic delays around the airport, the precast had to be delivered during the very early morning hours.

Trucking the panels to the site presented a special challenge to the precasters, according to Guy Bouchard, vice president and chief engineer at BPDL. Because the panels were large and included two window openings in each, they were fragile. To prevent breakage, the precaster had to design special racks to hold the panels on the trailers. The process worked well, resulting in no delivery delays or panels that were rejected because of poor quality, Bouchard reports. There also was no damage during erection, and every piece fit into its location, Johnson adds.

"A major advantage in using precast is the variety of exterior façade concepts that are possible. Panels can be virtually any colour, texture, shape and size."
Gary Johnson, principal
Cambridge Seven Associates Inc.

Architect: Cambridge Seven Associates Inc.
Engineer: Weidlinger Associates Inc.
Owner: Hilton Hotels Corp.
General Contractor: Beakon Skanska Construction Co.
Architectural Precast: Bétons Préfabriqués Du Lac Inc., Alma, QC