Novel experimental method to determine crack-bridging constitutive relationship of SHCC using digital image processing

Abstract

As the crack-bridging constitutive relationship (σ–δ) plays an important role in the multiple cracking behavior of strain-hardening cementitious composites (SHCCs), careful control of σ–δ relationship is the key to the successful design of SHCCs. Due to the multiple cracking nature of SHCCs with tight crack spacing, direct measurement of σ–δ constitutive relationship over a single crack is challenging, as any reasonably sized physical gauge length would cover the opening displacements of a number of subparallel cracks, therefore masks the true value. This study uses the Digital Image Processing method to capture the opening of a single crack in a double edge-notched SHCC specimen under tension, and the test results are compared with a previous method based on the displacement over a gauge length and theoretical simulation based on micromechanics. The proposed test method is intended to support future SHCC designs, for the experimental determination and theoretical calibration of the σ–δ relationship.