Use of Chemical Admixtures in Concrete Platforms


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Title: Use of Chemical Admixtures in Concrete Platforms

Author(s): H. Ronneberg

Publication: Special Publication

Volume: 119


Appears on pages(s): 517-534

Keywords: admixtures; air entrainment; compressive strength; concretes; high-strength concretes; offshore structures; plasticizers; slip-form construction; Materials Research

Date: 9/1/1989

Chemical admixtures in concrete are commonly used in Norway. About 95 percent of all ready-mixed concrete contain plasticizing admixtures, at about 2 l per m3 concrete. This is due to a high level of knowledge in concrete technology in Norway, mainly because of the activity in the North Sea and the construction of the concrete platforms. The concrete used in the first platforms, constructed in the middle of the 70s, contained ordinary plasticizing admixtures based on lignosulfonates. However, increasing demand for better workability with a slump greater than 220 mm, higher compressive strength, and therefore less water, and air entrainment in the flowing concrete has led to a more sophisticated use of chemical admixtures in concrete. In this respect, superplasticizers have become indispensable. Different kinds of superplasticizers combined with retarders and accelerators are important for strength and workability, as well as for controlling the slipforming process which may vary from 0.5 to 4.7 m every 24 hr. The slipforming operation of the shafts on the platform was finished in December 1986. Four different admixtures were used at the same time. For the first time, the slipforming rate was limited by the pouring capacity and not by the setting time of the concrete.