Issue34

J. Saliba et alii, Frattura ed Integrità Strutturale, 34 (2015) 300-308; DOI: 10.3221/IGF-ESIS.34.32 300 Focussed on Crack Paths Experimental analysis of crack evolution in concrete by the acoustic emission technique J. Saliba Université de Bordeaux, Institut de Mécanique et d’Ingénierie (I2M), Département Génie Civil et Environnemental (GCE), Talence, France j.saliba@i2m.u-bordeaux1.fr A. Loukili, J.P. Regoin LUNAM Universite, UMR-CNRS 6183, Ecole Centrale de Nantes, Institut de Recherche en Génie Civil et Mécanique (GeM), Nantes, France ahmed.loukili@ec-nantes.fr ; Jean-Pierre.Regoin@ec-nantes.fr D. Grégoire, L. Verdon, G. Pijaudier-Cabot Université de Pau et Pays Adour, Laboratoire des Fluides Complexes et leurs Réservoirs, LFC-R UMR5150, Anglet, France david.gregoire@univ-pau.fr ; laura.verdon@univ-lorraine.fr; Gilles.Pijaudier-Cabot@univ-pau.fr A BSTRACT . The fracture process zone (FPZ) was investigated on unnotched and notched beams with different notch depths. Three point bending tests were realized on plain concrete under crack mouth opening displacement (CMOD) control. Crack growth was monitored by applying the acoustic emission (AE) technique. In order to improve our understanding of the FPZ, the width and length of the FPZ were followed based on the AE source locations maps and several AE parameters were studied during the entire loading process. The b- value analysis, defined as the log-linear slope of the frequency-magnitude distribution of acoustic emissions, was also carried out to describe quantitatively the influence of the relative notch depth on the fracture process. The results show that the number of AE hits increased with the decrease of the relative notch depth and an important AE energy dissipation was observed at the crack initiation in unnotched beams. In addition, the relative notch depth influenced the AE characteristics, the process of crack propagation, and the brittleness of concrete. K EYWORDS . Concrete; Crack; Acoustic Emission technique; Notch depth; Unnotched beams. I NTRODUCTION racture of concrete is accompanied by the formation and evolution of an inelastic zone, referred to as the fracture process zone (FPZ), around the propagating crack tip. The existence of the FPZ is responsible of the nonlinear behaviour of concrete and lead to complex phenomena as size effects. In fact, the length and the width of the FPZ F