The role of microcracking on the compressive strength and stiffness of cracked concrete with different crack widths and angles evaluated by DIC

Abstract

In this study, uniaxial compression tests using cracked concrete with different crack widths and angles were conducted. The purpose of this study is to clarify influence of crack angle on the compressive fracture process and to understand the reduction mechanism of compressive strength and tangential stiffness due to a primary crack. In this experiment, the changes in strain distribution at the cutting surface during loading were determined by DIC, with the stress-strain relationship and tangential stiffness change during loading clarified. As a result, it was found that the relationships between compressive strength reduction and crack width change corresponding to crack angle. The reduction of compressive strength due to a primary crack in a direction intersecting with the loading axis (crack angle of 0–60°) is related to microcracks generated by shear deformation in a crack plane with accompanying aggregate interlock and closure of the primary crack. The reduction mechanism of compressive behaviors due to a primary crack parallel to the loading axis (crack angle of 90°) is also related to microcracks around the primary crack. However, the reduction of compressive strength and maximum tangential stiffness are lower in comparison to a crack angle of 60° due to area where the microcracking occurs being smaller due to aggregate interlock and closure of the primary crack occurring at only the crook of the primary crack. Finally, it was found out that the reduction mechanism could be interpreted by generation and propagation of microcracks from the primary crack even if the crack angle varies.