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Enhancing the performance of cementious composite through hooked end steel fibres and cement replacement materials

Student thesis: Doctoral Thesis

The aim of this study is to investigate the mechanical behaviour of concrete reinforced by hooked end steel fibres with the effects of cement replacement materials and fibre properties on the fibre-matrix bond. The mechanical performance and specifically the pullout behaviour of steel fibres with different hook shapes and tensile strengths in various cementitious material are studied. This research also aims to investigate the behaviour of steel fibre reinforced concrete in precast jacking pipes.
The cement replacements which have been used in this research included silica fume, pulverised fuel ash, limestone filler and ground granulated blast-furnace slag. In total, more than 1000 samples have been manufactured for experimental research on compressive strength, flexural behaviour of steel fibre reinforced concrete and pullout behaviour of hooked end steel fibres from cement based matrices. The effects of various parameters, such as water/binder ratio, cement replacement material type and level, hooked end shape and tensile strength of fibre on fibre–matrix pullout behaviour were determined. The results of tests and analysis indicated that improving hook shape of fibre increase the pullout strength by more than 200% and using cement replacement materials significantly influence the pullout behaviour which would be useful for the optimisation of steel fibre reinforced concrete and supporting the standardisation of pullout test.
In order to investigate the performance of steel fibre reinforced concrete in an application which this material has not been used before, mechanical properties of steel fibre reinforced concrete including compressive, tensile and flexural strength properties were experimentally determined. The results were also input into finite element modelling software package DIANA in order to define the material and to model the behaviour of jacking pipes under crushing load. A laboratory-scale research was conducted on steel fibre reinforced concrete pipes. The results show a 100% improvement in maximum crushing load with inclusion of fibres compared to the plain concrete. Full-scale jacking pipes including pipes with 450-1200 mm diameter and various reinforcement systems were also tested in accordance to BS EN 1916. According to the testing and modelling analysis, in order to use steel fibre as sole reinforcement and to achieve the crushing test criteria of the relevant standard, either the mechanical properties of the material or the geometrical properties of pipes needed to be amended. Full and partial replacement of bar reinforcement by type IV steel fibres were considered as well as the potential to increase the level of cover of reinforcing bar in order to produce pipes meeting higher exposure classes. The designs obtained present the possibility of production of pipes meeting higher durability/service life requirements than is possible with the existing products. The outcome of this research may be useful to widen the potential applications of the material across civil engineering.
Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date10 Jan 2019

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