Explosive Spalling of Ultra-High Performance Fibre Reinforced Concrete Beams Under Fire

C Kahanji, F Ali, A Nadjai

Research output: Contribution to journalArticle

15 Citations (Scopus)
14 Downloads (Pure)

Abstract

Purpose
The purpose of the study was to investigate the spalling phenomenon in ultra-high performance fibre reinforced concrete (UHPFRC) beams on exposure to a standard fire curve (ISO 834) under a sustained load.

Design/methodology/approach
The variables in this study were steel fibre dosage, polypropylene (PP) fibres and loading levels. The research investigated seven beams – three of which contained steel fibres with 2 vol.%, another three had steel fibres with 4 vol.% dosage and the seventh beam had a combination of steel fibres (2 vol.%) and PP fibres (4 kg/m3). The beams were tested for 1 h under three loading levels (20, 40 and 60 per cent) based on the ambient temperature ultimate flexural strength of the beam.

Findings
Spalling was affected by the loading levels; it exacerbated under the load level of 40 per cent, whereas under the 60 per cent load level, significantly less spalling was recorded. Under similar loading conditions, the beams containing steel fibres with a dosage of 4 vol.% spalled less than the beams with fibre contents of 2 vol.%. This was attributed to the additional tensile strength provided by the excess steel fibres. The presence of PP fibres eliminated spalling completely.

Originality/value
There is insufficient research into the performance of UHPFRC beams at elevated temperature, as most studies have largely focussed on columns, slabs and smaller elements such as cubes and cylinders. This study provides invaluable information and insights of the influence of parameters such as steel fibre dosage, PP fibres, loading levels on the spalling behaviour and fire endurance of UHPFRC beams.
Original languageEnglish
Pages (from-to)328-348
JournalJournal of structural Fire Engineering
Volume7
Issue number4
Early online date12 Dec 2016
DOIs
Publication statusE-pub ahead of print - 12 Dec 2016

Keywords

  • Fire resistance
  • Polypropylene
  • Ultra high-performance fibre reinforced concrete
  • ISO 834
  • Concrete beams
  • Steel fibres
  • Spalling

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