The new St. Louis Art Museum addition was designed by London-based architect David Chipperfield. The more-than-200,000-square-foot expansion will provide new galleries, public space, and more than 300 parking spaces in a belowgrade parking garage, as well as a new, fully accessible entrance on Fine Arts Drive.

As part of the design, ceiling coffers were used to provide a distinctive look for the new building. These coffers also provide the means for a unique lighting system in the building that will combine both diffused artificial and natural light.

Architect of Record: Hellmuth, Obata + Kassabaum
Project Manager: Rise Group
General Contractor: Tarlton/Pepper/KAI Joint Venture
Concrete Contractor: McCarthy Building Companies, Fenix Construction
Concrete Supplier: Breckenridge Material Co.

The concrete contractor for these coffers was St. Louis-based McCarthy Building Companies and the ready-mix concrete was supplied by Breckenridge Material Co. of St. Louis. The mix used for the application was a specially designed architectural self-consolidating concrete (SCC) that achieved slump flows of up to 34 inches without exhibiting any segregation. All formwork was constructed using Peri Fin-Form to achieve the extremely tight engineered specifications, which included a light reflectance of over 55%. This particular specification was met by using a combination of specialized formwork, an architectural SCC concrete, and titanium dioxide pigment added to the concrete mixture.

All placements were supplied at delivery rates of approximately 200 cubic yards/hour in order to maintain a constant flow through the pumps, thereby reducing the potential for any entrained air bubbles that could result in bug holes. Then the mix was permitted to flow horizontally up to 50 feet, which resulted in a smooth uniform surface and very sharp edges of the finished boxes. Placements were planned with the architects to ensure clean, smooth lines between pour joints because the concrete was the finished surface.

The exterior facade of the new building is being covered with polished concrete tilt-up panels. The contractor Fenix Construction, St. Louis, began with concrete supplied once again by Breckenridge Material Co. This particular concrete material is designed to achieve a very specific finish. The mix was comprised of a combination of 2-inch Dresser Trap rock and sand from Wisconsin as well as local gravel from the Meramec River. An integral liquid, black pigment was added, resulting in a black matrix for the exposed, polished surface. The result is a stunning facade for the building that is very distinctive and in stark contrast to the older architecture of the original art museum building.

The combination of these highly engineered mixes made this project one of the most technically challenging concrete construction jobs in St. Louis in recent years. Its success provides residents with a building made almost entirely out of concrete—that in and of itself represents a work of art.

Submitted by Sam Klucker, @The_Klucker.

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