Condensed Silica Fume in High Strength Concrete for Offshore Structures--A Case Record


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Title: Condensed Silica Fume in High Strength Concrete for Offshore Structures--A Case Record

Author(s): M. Sandvik, A. K. Haug, O. S. Hunsbedt, and J. Moksnes

Publication: Special Publication

Volume: 114


Appears on pages(s): 1117-1130

Keywords: admixtures; air-entrained concretes; field tests; plasticizers; high-strength concretes; mix proportioning; offshore structures; pumped concrete; silica fume; slipform construction; stability; workability; Materials Research

Date: 5/1/1989

Since 1971, a contracting firm has produced approximately 1.3 million m3 of high-strength concrete for offshore platforms in the North Sea. The major part of this concrete volume has been produced without condensed silica fume (CSF), fly ash, or any other pozzolanic material. For the company's latest project, moderate dosages of CSF in combination with high dosages of superplasticizing admixtures have been introduced to meet new demands in design and construction. The predominant requirements for concrete for extremely dense reinforcement (500 to 1000 kg/m3) are high workability (slump of approximately 250 mm) and negligible bleeding or segregation. Concrete mixes fulfilling these requirements and still having a moderate content of cement have been designed by adding 2 percent (by weight of cement) of CSF. Slipform construction and concrete pumping are vital elements in the construction procedures for very large offshore structures. CSF, through extensive full scale field tests and shaft slipforming, has been found to improve the pumpability and stability of high strength/high workability concrete mixes.