Micromechanical prediction of the flexural behavior of self-compacting ultra-high performance concrete (SC-UHPC)

This study aimed to investigate the effect of fiber volume fractions (Vf=0.5 %, 1.0 %, 1.5 % and 2.0 %) on the flexural behavior of SC-UHPC and to predict the flexural performance based on micromechanics analytical technique that considered the fiber distribution characteristics and a numerical analysis model for fiber pullout. The flexural tests were conducted on SC-UHPC, and image analysis methods were adopted to quantitatively estimate the fiber distribution characteristics on the fracture surface of SC-UHPC. The results showed that the fiber orientation (θ) of SC-UHPC tended to be parallel to the direction of the flexural loading and was mainly distributed between π/4 and π/3; the fiber bridging effect was quantitatively evaluated by introducing a numerical analysis model for fiber pullout and a fiber distribution probability distribution function (PDF); the flexural behaviors of SC-UHPC were predicted by employing the matrix softening and fiber bridging curves, and the analytical results were in good agreement with the experimental results. © 2025 Institution of Structural Engineers.