Fire Resistance of High-Strength Concretes for Offshore Concrete Platforms

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Title: Fire Resistance of High-Strength Concretes for Offshore Concrete Platforms

Author(s): George C. Hoff

Publication: Special Publication

Volume: 163

Issue:

Appears on pages(s): 53-88

Keywords: density (mass/volume); fiber reinforced concretes; fire resistance; high-strength concretes; hydrocarbons; lightweight aggregates; lightweight concretes; offshore structures; polypropylene fibers; underwater structures; Materials Research

Date: 8/1/1996

Abstract:
The fire resistance of high-strength (greater than 60 MPa) concretes has been reported to be reduced when compared to normal strength concrete. This behavior has been attributed to the very dense concrete matrix usually associated with high-strength concrete. This dense matrix does not allow rapid transmission of water vapor within the concrete exposed to high temperatures, thus leading to disruptive vapor pressures. This problem is aggravated further when the fire is a hydrocarbon fire which reaches 880 C within three minutes. Offshore concrete platforms, which are typically built with high-strength concrete, are therefore at risk from hydrocarbon fires. This paper presents the results of two test programs involving hydrocarbon fires and high-strength concretes. Both lightweight aggregate concrete and modified normal density concrete (blends of normal density and lightweight aggregate coarse aggregates) were evaluated. Small beams of lightweight concrete, using different lightweight aggregate types, were evaluated for spalling resistance. Polypropylene fibers, used in some beams, were successful in greatly reducing spalling. Large wall sections of modified normal density concrete experienced significant spalling, but retained adequate concrete strength behind the reinforcing bars because of the low rates of heat transfer within the large sections.