Damage investigation of single-edge notched beam tests with normal strength concrete and ultra high performance concrete specimens using acoustic emission techniques

The non-intrusive and non-destructive Acoustic Emission (AE) techniques acquire and analyze the signals emitted from the deformation or fracture of materials under external loading. In this study, the AE techniques with statistical analysis were used to study the damage process of single-edge notched beam (SEB) tests with normal strength concrete (NSC) and ultra high performance concrete (UHPC) specimens. The SEB tests with the lab-prepared NSC and UHPC specimens were conducted by employing a clip-gauge controlled servo-hydraulic testing system and an AE damage detection system. It was found that the cumulative AE events with respect to the crack mouth opening displacement (CMOD) or the crack tip opening displacement (CTOD) correlate to the mechanical loading of the specimens. A Weibull rupture probability distribution was proposed to quantitatively describe the mechanical damage behavior under the SEB test. A bi-logarithmic regression analysis was conducted to calibrate the Weibull damage distribution with detected AE signals and to predict the damage process as a function of the crack opening displacements. The calibrated Weibull damage functions were compared among NSC and UHPC specimens with different notch depths and locations. More AE damage events were detected for the specimen with larger notch-depth at the beginning of the damage process due to a higher initial stress concentration factor KI. The offset-notched specimen also produced more AE damage events due to shear damage effects. The results indicate that the calibrated Weibull rupture probability functions with AE event data can be applied to study damage processes under mechanical loading for brittle materials such as concrete.