ONLINE EXCLUSIVE Precast Concrete Proves Its Mettle Designing an appropriate façade for The Jasper required an in-novative solution. Stakeholders were initially skeptical about precast concrete, which had never been used in a historical Charleston, S.C., context, particularly thin-brick-clad precast concrete panels, says architect John Bedell of LS3P. Several meetings were held to educate neighborhood groups and local design review board members about architectural precast concrete, which allows detailing to exceed code-related masonry corbeling limitations. The structural capacities of con-crete and reinforcing combined surpass that of masonry, which is critical for producing a level of authenticity when emulating historic brickwork. Architectural precast concrete uses a high-density concrete (5000 psi) and con-ventional reinforcing bar and offers more flexibility in profile and detail. The typical panel thickness is 8 in., with a minimum thickness of 5 in. Joints between panels are usually ¾ in. and must be carefully planned with the precast concrete pro-ducer to avoid telegraphing individual precast concrete pieces. “This is particularly important when designing buildings inspired by historic building precedents,” Bedell says. Because Charleston is in a high-seismic zone, the seismic joint was 2¼ in. wide. The design team worked with Gate on a solution that would camouflage the joint, eventually locating it at the inner corners of the building, along with some special window details. The success of the architectural precast concrete strategy for The Jasper demon-strates that the system is an advanta-geous option for new buildings in historic contexts, says Bedell. “In addition to the ability to create ar-chitectural elements that complement and enhance the built environment, ar-chitectural precast can reduce cost and accelerate construction,” he says. Mock-Ups Showcase Precaster’s Expertise Initial mock-up panels were provided by two separate fabrica-tors competing for the project, says Bedell. “The panels not only showcased their craftsmanship and technical skills, but also served as exhibits to educate the members of the Design Review Board,” he says. Once Gate Precast Company won the bid, the next round of mock-ups involved determining the color of the thin-brick ve-neer and texture selection, as well as the precast concrete mixture proportions. Four separate 4 × 4-ft panels were created with various brick and precast concrete colors, and the selections were narrowed down to two brick colors, one for the field brick of the office and residential tower and the other for the parking structure. The design team also selected the exposed precast concrete color that best simu-lated limestone. The brick color for the office and residential tower is a special blend supplied by the Belden Brick Co. Once the color selections were finalized and the brick selections met PCI standards for freezing-and-thawing cycles and pull tests, Gate Precast Company fabricated four panels representative of the building façades and associated details. The average size of the panels was 8 × 15 ft, and cost the developer an estimated $250,000, including all mock-up materials and installation labor. “The Design Review Board approved the mock-up panels, but not without testing Gate’s capabilities for field repairs,” says Be-
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