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Title: Fibre distribution characterization and its impact on mechanical properties of ultra-high performance fibre reinforced concrete
Author: Li, L.
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Ultra-high performance fibre reinforced concrete (UHPFRC) is the most innovative cement based engineering material. It is also a big leap for the performance of this engineering material. The mechanical properties of UHPFRC not only depend on the properties of concrete matrix and fibres, but also depend on the interaction between these two elements. Moreover, this reaction is highly influenced by the fibre volume content distribution and fibre orientation distribution. Previous researchers had developed different methods to test the fibre distribution. However, apart from a genral fibre effciency reduction factor, there was no quantified relationship between the different fibre distribution and its corredponding mechanical performance. This research focuses on testing the fibre distribution and investigating their influences on the mechanical properties of UHPFRC. This research adopted the C-shape ferromagnetic probe inductive test. The effective depth of the magnetic probe was determined, and then this method was applied for testing the specimens with different thicknesses to obtain fibre volume content and fibre orientation angle. Image analysis was carried out on a number of specimens to prove the accuracy of the magnetic probe inductive test. Mechanical tests including compressive tests, uniaxial tensile tests and bending tests were carried out after the fibre distribution tests. The level of material performance enhancement is dependent on the fibre volume content and orientation angle. For tensile performance, the low dosage of fibres has little enhancement on the peak tensile/bending strength. Linear relationships can be found between the peak uniaxial tensile strength and fibre distribution with higher fibre dosages. This relationship was then further proved using the OpenSees programme. From the industrial point of view, over-dosing with fibres increases the construction cost. Furthermore, it may cause non-uniform fibre distribution and early concrete cracking. In order to improve the tensile behaviour of UHPFRC, adjusting the fibre orientation angle rather than simply increasing fibre volume content can be considered.
Supervisor: Xia, Jun ; Chin, Chee ; Jones, Stephen Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral