Properties of Concretes for Thin Underwater Placements and Repairs

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Title: Properties of Concretes for Thin Underwater Placements and Repairs

Author(s): Weston T. Hester, Kamal Henry Khayat, Jr.

Publication: Special Publication

Volume: 114

Issue:

Appears on pages(s): 713-732

Keywords: adhesion; admixtures; concretes; durability; fly ash; repairs; silica fume; strength; underwater structures; Materials Research

Date: 5/1/1989

Abstract:
Many marine and hydraulic structures must be constructed and repaired while submerged under water. Frequently, this requires placement of relatively thin (0.5 m or less) layers of concrete to fill voids in exposed surfaces or submerged formwork. Concretes placed underwater should flow readily and with little segregation and resist erosion from underwater currents. The hardened concrete should achieve excellent adhesion to underlying surfaces and develop high strengths. To achieve the desired performance, the concrete should contain a moderate amount of anti-washout admixture, a cement content of approximately 350 kg/m3, 25 kg/m3 of silica fume to enhance durability, and 18 kg/m3 fly ash to improve workability of the fresh concrete. A hard, natural gravel, representing approximately 54 percent of the aggregate content, should be used for wear resistance, and with the lowest possible w/c (0.41 ñ 0.03, typically) consistent with placement requirements, to maintain strengths. Prior to the actual field placement, several rheological and mechanical properties should be determined to insure proper placability, homogeneity, and therefore increase the success probability and cost effectiveness of site trials and subsequent actual field placements.