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55H Street – Georgetown Graduate Student Hall

Location: Washington, DC

Award: Lower Carbon Concrete

Project Team

Owner: Georgetown University

General Contractor: John Moriarty & Associates of Virginia

Architect: Robert A.M. Stern Architects

Engineer: SK&A

Concrete Contractor: Belfast Valley Concrete

Slag Cement/Concrete Supplier: Holcim US

55 H Street is a 12-story student housing building for Georgetown University, Washington, DC, USA, near the U.S. Capitol. This project is located in the area adjacent to its downtown and law campuses. The building will feature first- and 12th-floor amenities, with the ability to host events in the 12th-floor amenity space. The development includes 4200 ft2 (390 m2) of university space, 1980 ft2 (185 m2) of retail space, and large landscaped courtyards.

The total concrete volume was 8632 yd3 (6600 m3). Slag cement was used in 100% of the project’s concrete mixtures, with cement replacement rates ranging from 35 to 70%. Low-carbon mixtures containing as much slag cement as possible was used for each application to lower the mixture’s carbon footprint, while maintaining performance and workability.

ECOPact concrete with slag cement proved to be the ideal high-performance solution, meeting the general contractor’s speed of construction goals for the project. The low-carbon mixture provided high-performance, meeting the specified high early-strength requirements, and helping work crews to meet schedule demands to allow other trades to begin work on the building’s façade.

Application Type

% Slag Cement Replacement


% Portland Cement


% Portland Limestone Cement

% Other SCM (if applicable)


1700 lbs 3/8” pea stone + 1420 lbs sand

Water/cement ratio


7-day strengths

3,000 psi

28-day strengths

5,000 psi


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