Issue 40

S. K. Kourkoulis et alii, Frattura ed Integrità Strutturale, 40 (2017) 74-84; DOI: 10.3221/IGF-ESIS.40.07 74 Focussed on Recent advances in “Experimental Mechanics of Materials” in Greece Pre-failure indicators detected by Acoustic Emission: Alfas stone, cement-mortar and cement-paste specimens under 3-point bending Stavros K. Kourkoulis, Ioanna Dakanali Laboratory of Testing and Materials, Department of Mechanics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou Campus, 157 73 Athens, Greece stakkour@central.ntua.gr, ioannadak@hotmail.com A BSTRACT . Acoustic Emission (AE) is the technique most widely used now- adays for Structural Health Monitoring (SHM). Application of this technique for continuous SHM of restored elements of stone monuments is a challenging task. The co-existence of different materials creates interfaces rendering “identi- fication” of the signals recorded very complicated. To overcome this difficulty one should have a clear overview of the nature of AE signals recorded when each one of the constituent materials is loaded mechanically. In this direction, an attempt is here described to enlighten the signals recorded, in case a series of structural materials (natural and artificial), extensively used for restoration projects of classic monuments in Greece, are subjected to 3-point bending. It is hoped that obtaining a clear understanding of the nature of AE signals re- corded during these elementary tests will provide a valuable tool permitting “identification” and “classification” of signals emitted in case of structural tests. The results appear encouraging. In addition, it is concluded that for all materials tested (in spite their differences in microstructure and composition) clear pre- failure indicators are detected, in good accordance to similar indicators pro- vided by other techniques like the Pressure Stimulated Currents (PSC) one. K EYWORDS . Alfas stone; Mortar; Cement paste; Three-point bending test; Pre-failure indicators; Acoustic Emission. Citation: Kourkoulis, S.K., Dakanali, I., P Pre-failure indicators detected by Acoustic Emission: Alfas stone, cement-mortar and cement-paste specimens under 3-point bending, Frattura ed Integrità Strutturale, 40 (2017) 74-84. Received: 11.01.2017 Accepted: 07.03.2017 Published: 01.04.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION or the restoration of fragmented structural elements of stone monuments a pioneering technique has been developed by the scientists working for the restoration of the Acropolis of Athens. According to this technique, the fragmented structural members are rejoined together by inserting threaded titanium bars into pre-drilled holes, F