Designed by Handel Architects, the Rowan utilizes exposed structural cast-in-place concrete as a key architectural design element. Located in the old industrial wing of San Francisco, CA, the Rowan consists of 71,500 sq. ft. of mixed-living and residential space.
Slag cement was utilized in all concrete elements of the 5,200 yd3 structure, replacing 34% percent of the total cementitious material. The footing, column, and wall mixes consisted of ternary mixes with 50% replacement of cement to optimize workability and durability. The post-tensioned decks and tower crane pad mixes were a blend of Slag and Type III cement to reach strengths of 4000 psi (27.6 MPA) in 2 days.
Slag cement was used throughout the project – in all concrete mixes – for durability. The column, wall, and footing mixes consisted of ternary blends of cement, fly ash, and slag -- with slag making up 30% of the blend. Post-tensioned decks were a mix of Pronto Type III cement and 30% slag with a specification requirement of 3000 psi in 3 days. The crane pad and some elevated decks that required 4000 psi in 2 days were a 50/50 blend of Slag and Type III cement.
Slag was crucial to the strength, speed, and constructability of the project. The strengths needed to keep pace with the accelerated schedule would not have been possible without the gains attributed to slag.
The architect purposefully wanted those on the street to see the structural components of the building. As a result, other than a few columns inside, the architect took all the structure to the exterior of the building maximizing tenant and rental space. The structural system, known as an exoskeleton is already turning heads, with the cast-in place concrete on full view.
Project credits: Trumark Urban, Owner; Handel Architects, Architect; Nishkian Menninger, Engineer; Build Group, Contractor; Central Concrete Supply Company, Inc., Concrete; Lehigh Hanson, Slag Cement