An improved image processing method for assessing multiple cracking development in Strain Hardening Cementitious Composites (SHCC)

Strain Hardening Cementitious Composites (SHCC) exhibit tension-hardening behavior accompanied by the formation of multiple cracks. To study the multiple cracking process, cracks are identified from digital images. As conventional image processing technique based on a single threshold of gray intensity cannot accurately determine the width of both fine and wide cracks, a new double-threshold algorithm is developed and its accuracy is verified by comparing with direct measurement under the microscope. Then, an additional algorithm for removing the noises and isolating individual crack regions is introduced. With the improved image processing method applied to a large number of sequential images, detailed information on the development of crack number and width is acquired. The average value and deviation of crack width at a given strain can be calculated to facilitate durability design. Also, with the stress-crack width relation obtained for various cracks, the fiber distribution among cracked sections can be estimated.