No abstract

No abstract

Ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) is a relatively new construction material. In comparison with conventional high‐strength concrete, UHPFRC does not usually contain coarse aggregates larger than 6–7 mm in size. This paper presents the outcomes of an experimental study of UHPFRC beams subjected to four‐point loading. The effect of two parameters was studied, namely, the fiber content and the temperature of the curing water. Eight UHPFRC beams were tested, comprising six beams reinforced with rebars and two beams without rebars. Three fiber contents were investigated in this study (1, 2, and 4% in volume). The study investigated two curing temperatures of water, 20 and 90°C. The results presented in this paper include deflections, toughness energy, and moment capacity and also includes a comparison with calculations according to EC2 provisions. A minor difference was observed in the deformation and flexural behavior of beams with fiber contents of 1 and 2% (in volume). However, beams with 4% (in volume) fibers exhibited a higher flexural capacity. Only flexural failure was observed and no shear‐related failure was recorded. Beams with 1% (in volume) fibers for both curing regimes had the highest peak load toughness energy. Beams reinforced with rebars and cured at 20°C had a significantly higher bending resistance.

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.

Developing an experimental database of burning characteristics of combustible informal dwelling materials based on South African informal settlement investigation