Characterization of the mechanical properties of Ultra High Performance Fibre-Reinforced Concretes (UHPFRC)

Abstract

Ultra High Performance Fibre-Reinforced Concrete (UHPFRC) is a recent kind of concrete which incorporates characteristics of Self-Compacting Concrete (SCC), Fibre-Reinforced Concrete (FRC) and Ultra High Performance Concrete (UHPC). Usually steel fibres are used as reinforcement, but since this material is sensitive for corrosion and in addition quite dangerous when protruding outside the surface, a new kind of reinforcement is under development: polymer fibres. As UHPFRC is not an ordinary concrete, it is necessary to analyse its behaviour. As there is almost no information available in literature about UHPFRC reinforced with polymer fibres, this thesis focusses on its tensile behaviour. This is examined by performing Barcelona tests for different kinds of dosages, changing the sand composition, water content and fibre composition. Results show that the sand composition has no clear effect on both the tensile strength of the cement matrix and the ductility. The water content has a clear effect on the tensile strength of the cement matrix: the higher the content, the lower the strength. In contrast, it has no effect on the ductility: in all cases the fibres have a good binding with the cement matrix and are mostly broken and not pulled out. Last, the fibres have no effect on the strength of the cement matrix, but even more is the effect on the ductility: results show that in case two different kinds of fibres are used, the ductility is improved. Although the results show that the amount of fibres may be increased to improve even more the ductility. This implements a decrease in workability, which can be solved by adding more water, but this implements a decrease of the strength of the cement matrix. Consequently, an intermediate solution must be found between the desired strength of the cement matrix and the ductility