Modified Normal Density (MND) Concrete for the Troll GBS Platform


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Title: Modified Normal Density (MND) Concrete for the Troll GBS Platform

Author(s): M. Sandvik, T. Hovda, and S. Smeplass

Publication: Special Publication

Volume: 149


Appears on pages(s): 81-102

Keywords: aggregates; alkali-aggregate reactions; compressive strength; concrete platforms; concretes; creep properties; density (mass/volume); fatigue (materials); fracture properties; lightweight aggregates; modulus of elasticity; shrinkage; stress-strain relatio

Date: 10/1/1994

The troll GBS platform is the world's largest concrete offshore concrete platform. The platform is designed for an operational lifetime of 70 years and will be installed in the North Sea during 1995. To improve the buoyancy of the platform during tow-out to the field, a concrete mixture with reduced density has been developed, providing a characteristic 28-day cube compressive strength of at least 75 MPa and an in situ density of 2250 kg/m 3. The weight reduction has been obtained by partly replacing the natural coarse aggregates by high-quality lightweight aggregates. The concrete is denoted as modified normal density (MND) concrete. The modification was expected to reduce both compressive strength, Young's E-modulus, and material ductility to some extent. A comprehensive testing program comprising laboratory tests and full-scale tests has been performed to investigate and to document all relevant concrete properties related to mechanical, durability, and constructibility performance of the concrete. A secondary purpose of the investigations has been to evaluate the possibility of retaining the mechanical properties of the original normal density concrete by replacing the remaining coarse granite aggregate with a more rigid quartz-diorite aggregate. The laboratory investigations included the determination of the following concrete properties: fresh concrete properties, compressive strength development, compressive strength at sustained load, compressive E-modulus, tensile strength and E-modulus, stress-strain in compression, fatigue, fracture energy and characteristic length, shrinkage, creep, water intrusion, and alkali-silica reactivity.