Investigation of Distribution and Orientation of Fibres in Steel Fibre Reinforced Concrete using X-Ray Computed Tomography

Inclusion of steel fibres in concrete is a means of improving the properties of the material, especially its ductility. This study investigates the distribution and orientation of fibres in steel fibre reinforced concrete (SFRC) examining various factors influencing the distribution/orientation and the subsequent effects on post-cracking performance of SFRC. Variables selected for the study were fibre length (50 mm and 60 mm) and aspect ratio (45, 50 and 60) and maximum aggregate size (10 mm and 20 mm). 600 mm square slabs were tested under central loading and then cores were taken from the tested slabs for imaging using X-ray computed tomography (XCT). Image analysis was performed using the Toolkit software along with a bespoke programme to obtain numerical values summarising the distribution and orientation of the fibres. The results show a remarkable improvement in maximum failure load of all slabs containing fibres as well as improved performance when smaller aggregates were used. XCT image analysis highlighted a higher degree of randomness in fibre distribution and orientation when smaller aggregates were used in combination with any of the fibre types.