Fiber distribution in UHPC under different influencing factors evaluated with a novel method based on deep learning

Abstract

The dispersion of fibers in UHPC significantly affects its mechanical properties. Currently, conventional image analysis methods are employed to evaluate fiber dispersion. However, due to the settling of steel fibers in UHPC and the subjectivity of image processing, the evaluation of fiber dispersion is neither sufficiently thorough nor accurate. In this study, removal method was used to optimize a deep learning-based U-net model for fiber identification. And sinkage coefficient was proposed as a complementary index for evaluating fiber dispersion. Subsequently, the accuracy of both the identification technique and evaluation method was separately validated. Then, the image processing techniques and evaluation method proposed in this study are applied to investigate the impact of various factors on fiber distribution in UHPC. The results indicate that the optimized deep learning-based network accomplished batch image semantic segmentation and image denoising. This approach mitigated the subjectivity during threshold selection and minimized the influence of low-quality images on fiber identification. The proposed sinkage coefficient can reflect the impact of fiber sinking on its performance. This coefficient associate with distribution and orientation coefficients can evaluate fiber dispersion comprehensively. Experimental investigations revealed that during vibration, fibers in UHPC exhibit sinking or floating phenomena. The consistency of the slurry emerges as a pivotal factor affecting fiber dispersion. Lower consistency results in pronounced fiber sinking, whereas higher consistency induce fiber floating. The incorporation of coarse aggregate facilitates the formation of a network structure with steel fibers, thereby ameliorating fiber sinking or floating tendencies, further affecting the fiber dispersion. Additionally, the increase in vibration time is also detrimental to the uniform dispersion of fibers.