Effect of Steel Fibre Dosage on the Behaviour of Ultra High Performance Fibre Reinforced Concrete Beams and Slabs

Ultra High Performance Fibre Reinforced Concrete (UHPFRC) is a relatively new form of concrete that exhibits enhanced strength, ductility and durability properties in comparison to conventional fibre reinforced and high... [ view full abstract ]

Ultra High Performance Fibre Reinforced Concrete (UHPFRC) is a relatively new form of concrete that exhibits enhanced strength, ductility and durability properties in comparison to conventional fibre reinforced and high performance concretes. Use of UHPFRC reduces the section sizes that can be used in a structure, which in turn reduces the structure’s self-weight and the volume of concrete and raw aggregates used in its construction. However, a disadvantage of UHPFRC is that it results in a significant rise in material costs over normal and even high performance concretes. Therefore, the sustainability of this material must be improved to make UHPFRC a viable option for the construction industry. Costs are significantly higher in Ireland as certain constituents are not readily available. In this research a UHPFRC mix that uses locally sourced materials, where possible, has been developed to produce a more sustainably viable material for the Irish construction industry. The research reported here is focused on results from experimental tests on small scale UHPFRC beams and flat slabs with varying fibre dosages and cross sections, which were tested using a four point bending test and punching shear test respectively. Results from additional tests on specimens that included conventional steel bar reinforcement are also presented for comparison. The results obtained give an insight into the requirements for secondary reinforcement in UHPFRC structures, which is currently somewhat inconsistently defined in UHPFRC design guidelines and recommendations. The conclusions from this research will be applied to UHPFRC numerical modelling problems and aid in the development of design codes and guidelines.