High-temperature behaviour of HPC with polypropylene fibres: From spalling to microstructure

Abstract The addition of polypropylene (PP) fibres to high-performance concrete (HPC) is one way to avoid spalling of concrete under fire conditions. The present work contributes both to the understanding of the way in which fibres act and to optimising the fibre dosage. Pore pressure measurements performed on heated specimens showed that the presence of fibres led to a large decrease in the extent of the pressure fields that build up in the porous network during heating. This effect was also significant at dosages lower than the theoretical percolation threshold. These results are supported by permeability measurements carried out after various heat treatments and for various fibre dosages: they showed the striking effect of fibres from 200°C up, that is, very close to their melting temperature. The role of fibres is discussed through the analysis of concrete microstructure and fibre–matrix interactions as function of heat treatment.

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