Investigation on stress-crack opening relationship of engineered cementitious composites using inverse approach

The stress-crack opening relationship of engineered cementitious composites was determined with an inverse method. Four cement matrixes with water to cement ratio of 0.55, 0.45, 0.35, 0.25 and fiber contents of 0.5%, 1.0% in volume were selected to form different series of composites. The results show that the σ–w relationship of the cement matrix is instant strain softening after the cracking strength. After adding polyvinyl alcohol fibers, the stress-crack opening relationship of the composites changes to a double peak mode behavior as the crack bridging first decreases from cracking strength, then increases to the second peak. After that the tensile softening is displayed again with increase of crack opening. The cracking strength is governed by the cement matrix and the second peak stress is controlled by the fibers and fiber/matrix interface. The second peak is greatly increased with increase of fiber content. The second peak stress larger than the cracking strength means strain-hardening and multiple cracking performances can be expected under tension.