Detection of Crack Evolution in Plain Concrete by Electronic Speckle Pattern Interferometry

Abstract

In order to study crack evolution in concrete, Electronic Speckle Pattern Interferometry (ESPI) technique was applied to measure full-field displacement of concrete beam subjected to three-point bending. Basic principles of ESPI technique were introduced. Mid-span deflection and crack mouth opening displacement were measured by linear variable differential transformers (LVDTs) and clip gauge, respectively. Typical load-displacement curves measured by different methods were compared and analyzed. Analysis results indicated that ESPI results were in good agreement with that measured by LVDT (clip gauge), verifying the validity and accuracy of ESPI measurement. From displacement contours, crack evolution including its initiation and propagation was observed. Furthermore, strain profiles near the crack at different loading levels were determined. Strain profile was nearly linear before crack initiation and became nonlinear with crack growth.