EFFECT OF STRENGTH ON FIRE BEHAVIOUR OF CONCRETE

116 - EFFECT OF STRENGTH ON FIRE BEHAVIOUR OF CONCRETE 1. U-M. Jumppanen Technical Research Centre of Finland Fire Technology Laboratory M.Sc., Senior Research Scientist ABSTRACT The use of high strength concretes enhances the economy of structures, but this involves also a knowledge of their high temperature behaviour because the structures may be subjected to high temperatures (e.g. fire) and they must be correspondingly designed. High temperature behaviour of different high and ul tra high strength concretes has been investigated. Studies comprised mechanical properties and the chemical and physical background of their alteration due to heat- ing. The high strength concretes showed a stronger loss of strength and a higher risk of spalling than normal strength concretes. Key-words: Fire, High strength concrete. INTRODUCTION In recent years the development in concrete technology has made it possible to double - even triple - the compressive strength of concrete even applying customary production methods. Tradi- tionally the structural regulations and codes have included the concretes with compressive strength of 15 - 60 MPa. The use of high strength {HS-) concretes requires knowledge of their high temperature behaviour because the structures may - either in normal service or under catastrophic conditions - be subjected to high temperatures and they must be correspondingly designed. The failure of concrete structures in fire may have different reasons, e. g. ; fail ure of the conr;rete, steel or bond. The failure of the concrete can be caused by the reduction of its strength or often more drastically by destructive spalling. The high temperature properties have up to now usually been determined with normal strength (OS-) concretes. Extending the known data by linear extrapolation to cover also HS-concretes is not necessarily relevant, because due to their special composi- tion and microstructure they may show high temperature phenomena up to now not perceived with OS-concretes. In recent years fire properties of different types of concrete (OS-concretes (K20 and K50), HS-concretes (KlOO) and ultra high strength concretes (K200 even. K250)) have been investigated in Fire Technology

EFFECT OF STRENGTH ON FIRE BEHAVIOUR OF CONCRETE

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