Size effects on the characteristics of fracture process zone of plain concrete under three-point bending

Abstract

This paper studies the size effects on the characteristics of fracture process zone (FPZ) of plain concrete, including its physical features and softening behavior. Three-point bending tests were performed on pre-notched beams with similar geometry and different dimensions. Electronic speckle pattern interferometry (ESPI) technique was employed to monitor the crack evolution and full-field deformation of the beams. The development of FPZ was evaluated qualitatively based on the strain fields and quantitatively based on the displacement fields obtained by the ESPI technique. By adopting the incremental displacement collocation method, the tension softening curves (TSCs) of specimens with different sizes were estimated and approximated as bilinear curves. The features identified from the TSCs were correlated to the physical features in the development of FPZ. Finally, an empirical tension softening model and corresponding size-independent parameters were obtained based on the estimated TSCs of different sizes specimens.