Advances in Underwater Concreting: St. Lucie Plant Intake Velocity Cap Rehabilitation


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Title: Advances in Underwater Concreting: St. Lucie Plant Intake Velocity Cap Rehabilitation

Author(s): N. Hasan, E. Faerman, and D. Berner

Publication: Special Publication

Volume: 140


Appears on pages(s): 187-214

Keywords: admixtures; aggregates, high performance concretes; tests; marine atmospheres; mix proportioning; precast concrete; reinforced concrete; repairs; slabs; thermal properties; tremie concrete; velocity; underwater construction; Materials Research

Date: 9/1/1993

Underwater repairs to, and rehabilitation of, existing reinforced concrete velocity caps of the circulating water intake structure at St. Lucie Powerplant, Fort Pierce, Florida were made utilizing high-performance in a marine environment. Use of this repair technique avoided the necessity of constructing a cofferdam for repair work in the dry, and thus minimized interruption to plan operation, and resulted in considerable savings. Mix proportions for the high-performance concrete included cement, fly ash, silica fume, and antiwashout admixtures as well as high-range water-reducing and set-retarding admixtures. The mix proportions were tested extensively in the laboratory and field conditions to optimize the slump and the initial setting time of concrete while assuring early compressive strength requirements for conformance with the specified requirements. Large scale mock-up tests, utilizing both tremie and pumping methods, were conducted to simulate under water placement in the surf zone and to select the actual concrete placing method, rate of placement, and to identify surface preparation and protection requirements. Construction procedures for the new reinforced concrete slabs involving approximately 3000 yd 3 precast and tremie concrete utilizing a barge-mounted concrete batch plant; quality control and post-placement inspection measures are also discussed.