Tensile characteristics of strain-hardening cement-based composites with different curing ages

Abstract

This paper investigates tensile performances of strain-hardening cement-based composites (SHCC) with different curing ages varying from 3d to 28d. Cracking properties of SHCC specimens like the evolution of the number of cracks and the crack opening under direct tension was monitored simultaneously by using the digital images correlation (DIC) technique. Results show that the ultimate tensile strain in specimens cured for 7d is higher than that in specimens cured for 3d and 28d. The strain-hardening process involves three stages such as the initial, the intermediate, and the final stage, which are determined in terms of their cracking properties. Cracking properties of specimens cured for 3d and 7d display different rules from those of specimens cured for 28d at the intermediate strain-hardening stage, leading to different shape of stress-strain curve. Curing age influences fiber bridging stress-crack opening relation (σ(δ)) and interfacial mechanical behavior between PVA fiber and the matrix. σ(δ) gained by the DIC technique is similar to that observed in the tensile testing on notched specimens. The energy-based index of specimens cured for 7d has greater margin than that of specimens cured for 3d and 28d. The interfacial bond between fiber and matrix in specimens cured for 28d is larger than that in specimens cured for 3d and 7d.