Experimental Study on the FPZ Properties in Concrete Using ESPI Technique

Abstract

ESPI technique was used to measure full-field deformation of concrete beams subjected to three-point bend. LVDTs and clip gauge were used to measure the mid-span deflection and CMOD of the beam, respectively. By comparing ESPI results with the results measured by the other two instruments, the validity of ESPI technique was verified. The length of the FPZ was estimated from displacement contour and the crack tip was identified as the position where the displacement contour became continuous. In addition, the length of the FPZ was estimated from strain contour and the crack tip was judged based on the concept of tensile strain capacity. Analysis results indicated that the length of the FPZ estimated from the two methods were in good agreement. Furthermore, the lengths of the FPZ and COD profiles at different loading levels were evaluated.