Ultra High Performance Fibre Reinforced Concrete for Infrastructure Construction
Supervisor: Dr Tomas O’Flaherty
Funding Body: Institute of Technology Sligo Presidents Bursary Awards
All economies are now under pressure to deliver sustainable solutions for all infrastructure. Sustainable development requires that infrastructure, such as bridges are not only designed to be fit for purpose but also take account of the environmental impact of the whole life cycle of the structure, from ‘cradle to grave’. The performance and durability of the materials used in their design, such as concrete, need to be improved. The concretes of tomorrow need to adhere to sustainable development principles and the cost of 1 year of life cycle of a structure needs to be valued higher than the cost of producing 1m3 of concrete. Ultra-high performance fibre reinforced concrete (UHPFRC) can be used to improve bridge performance, extend their working life and reduce environmental impact. Furthermore, UHPFRC is a fast, efficient and price competitive method for the repair/rehabilitation of existing infrastructure.
However, the use of UHPFRC is currently limited by a shortage of design rules and guidelines, thereby preventing full advantage being taken of the material. One of the major issues relating to design rules is the requirement of secondary steel bar reinforcement. It is unclear where secondary reinforcement is required and in most cases products are over compensated for by adding excessive secondary reinforcement which reduces the sustainability of the product due to high economic costs and environmental impact associated with manufacturing steel.
While the use of UHPFRC has grown in other developed countries, it is relatively unknown in Ireland. The Irish concrete industry is discouraged by the high cost of producing UHPFRC but they have not considered the whole life cycle benefits of the material. By using UHPFRC stronger and more slender structures can be built than with conventional concrete. As a result, less raw aggregate and steel reinforcement will be used and the final product will be more aesthetically pleasing.
This research is focused on developing a new type of UHPFRC mix which is suitable for use in the Irish concrete industry. If correctly utilised this product can greatly enhance the sustainability of the Irish concrete industry and provide many long term benefits including longer life, significant cost savings and a reduction in the environmental impact. The project will use experimental testing to determine material behaviour in conjunction with numerical modelling to extrapolate the results to develop design rules which can be used to overcome design difficulties including the use of secondary steel reinforcement.
Numerical Modelling of Concrete Tensile Specimens
UHPFRC four point bending test