Enhancing the splitting tensile strength of UHPC with different fibre types and hybrid fibres

This study conducted an experimental investigation to evaluate the splitting tensile strength of ultra-high performance concrete (UHPC) and UHPC reinforced concrete (UHPFRC) incorporating different fibre types including copper-coated and hooked-end steel fibres, basalt fibres, polyvinyl alcohol fibres, polypropylene fibres, and hybrid fibres. The experimental results indicated the average splitting tensile strength ranges from 7.09 to 17.08 MPa, corresponding to fibre contents between 0% and 2%. In general, steel fibres enhance the splitting tensile strength of UHPC more significantly than synthetic fibres. The strength enhancement is more pronounced when the fibre content is increased from 1% to 2%. Under splitting tensile loading, all fibre-reinforced specimens exhibited ductile failure, retaining their original shape with varying degrees of cracking, while plain UHPC specimens performed brittle failure with splitting into two halves. Typical failure patterns and crack propagation stages are proposed for UHPC and UHPFRC. Furthermore, the experimental results demonstrated the use of hybrid fibres, achieved by partially substituting synthetic fibres with steel fibres, significantly enhances the splitting tensile strength. Finally, this study compiles formulae for predicting the splitting tensile strength from international standards and previous models. A comparison between the predicted and experimental splitting tensile strengths was conducted to confirm the suitability of the collected formulae.