Behaviour of hybrid PVA-steel fibre reinforced ultra high performance concrete at high temperature

摘要

Reactive powder concrete is an ultra-high performance concrete that exhibits superior strength,rndurability and ductility compared to normal concretes; this is due to its homogeneity, dense microstructurernand the presence of steel fibres. To best utilize the benefits of this material in construction, it is essential tornunderstand its behaviour under different loading conditions, with high temperature exposure being one of suchrnconditions. Reactive powder concrete containing only steel fibres or no fibres has been found to perform poorlyrnunder extreme temperatures due to explosive spalling caused by a build-up of pore water pressure within itsrndense micro-structure; this may be alleviated with partial replacement of steel fibres with PVA fibres. Thisrnpaper presents the behaviour of reactive powder concrete containing equal amounts of PVA and steel fibres,rnoccupying a total volume fraction of 2% and tested at high temperatures. The behaviour is characterized byrnmeasuring the stiffness and axial deformation at various temperatures and at stress levels of 30 per cent of therncylinder compressive strength determined at room temperature. The elastic modulus at high temperature wasrnfound to decrease gradually with temperature. Transient creep was observed to develop between 200℃ andrn300℃, increasing gradually with temperature thereafter.