Time Dependent Behaviour of Fibre Reinforced Concrete

Abstract

The use of fibre reinforced concrete (FRC) in industry is gaining traction. This is partially as a result of the material being included in recent design standards. However, standards do not yet contain meaningful provisions to describe the long-term serviceability behaviour of FRC. Furthermore, it is unclear if the short-term, well known, enhancements of FRC can be relied upon in time. Understanding the physical mechanisms of FRC in the long-term and including relevant provisions in standards is critical to maximise the benefits and use of FRC. The first part of this thesis presents a series of modelling approaches that can be used to predict the time-dependent serviceability performance of FRC. The thesis presents both a layered approach, enabling the analysis of evolving material properties in time, and a simplified model, which is more suitable for routine use. The second part of this thesis presents a novel experimental campaign, which investigates the early-age bond stress of FRC. The campaign experimentally observes the enhancements induced by the inclusion of fibres at early ages and presents modelling that correlates with the experimental data. The final part of this thesis experimentally investigates the time-dependent behaviour of FRC through six large-scale flexural beams subjected to a sustained uniformly distributed loading for two years, as well as eighteen tension chords subjected to a range of instantaneous sustained tensile loads. The thesis reports on the deformation and cracking behaviours that are currently not available in the literature. The results indicate that steel fibres lead to improved serviceability outcomes in the short-term, with this improvement maintained under sustained loading. While the inclusion of polypropylene fibres results in improvements in the short-term, these appear to diminish under sustained loading. The proposed models are compared to the experimental data and good correlations are observed.