Effects of flowability on SFRC fibre distribution and properties

In this study, the effects of the mix flowability on the steel fibre distribution patterns and mechanical properties of steel-fibre-reinforced concrete (SFRC) were investigated. Slump ranging from 80 mm to 200 mm was employed as the parameter to reflect the flowability of SFRC. The results showed that an increase of flowability had no influence on the orientation of steel fibres and led to a decrease of sectional uniformity. Steel fibres orientated in the longitudinal direction of higher-flowability SFRC tended to precipitate toward the bottom layer of the specimens. This resulted in much better flexural performance, including flexural toughness and fracture energy. Analysis of the data suggested that instead of studying the whole cross-section, the distribution rate and distribution coefficient of steel fibres in the tensile zone of specimens should be considered as the main factor determining flexural performance of SFRC. Calculations for bending stiffness and flexural stress based on the distribution rate of high-flowability SFRC are recommended. Moreover, owing to the layering effect of steel fibres, traditional test methods were identified as being unsuitable for determining the mechanical properties of SFRC, indicating that further investigation is required.