Quantitative evaluation technique of Polyvinyl Alcohol (PVA) fiber dispersion in engineered cementitious composites

The fiber dispersion in fiber-reinforced cementitious composites is a crucial factor with respect to achieving desired mechanical performance. However, evaluation of the fiber dispersion in the composite Polyvinyl Alcohol-Engineered Cementitious Composite (PVA-ECC) is extremely challenging because of the low contrast of PVA fibers with the cement-based matrix. In the present work, a new evaluation technique is developed and demonstrated. Using a fluorescence technique on PVA-ECC, PVA fibers are observed as green dots in the cutting plane of the composite. After capturing the fluorescence image with a Charged Couple Device (CCD) camera through a microscope, the fiber dispersion is evaluated using image processing and statistical tools. In the image processing step, the fibers are more accurately detected by employing a series of processes based on categorization, watershed segmentation, and morphological reconstruction. Test results showed that the dispersion coefficient αf was calculated reasonably and the fiber-detection performance was enhanced.