The seismic retrofit of Barker Hall a six-story 40-year-old concrete building on the University of California Campus in Berkeley required the construction of a concrete belt foundation with bonded post-tensioned -PT- tendons at the top and bottom. The belt foundation supports the new exterior shearwalls and collector beams that strengthen the structure. The shearwalls are heavily reinforced and serve as the exposed facade of the building. A strong committment to green building prompted the structural designer to specify high volume fly ash concrete -HVFA- requiring at least 50% replacement of cement by fly ash. The article contains a description of the materials mixture proportions construction practices and properties of the HVFA concrete used for Barker Hall s foundations and shearwalls. The experience with HVFA concrete at Barker Hall was very positive. Mixture proportion formulation followed by field trial proved to be invaluable in developing HVFA concrete mixtures that met the designer s criteria and expectations and were also accepted by the contractor.
Technical Report Author: P. K. Mehta, Dushyant Manmohan