Load-carrying capability and evolving crack damage of a cube-shaped concrete specimen have been assessed during a laboratory compression test carried up to fracture. Damage assessment has been carried by Acoustic Emission (AE) monitoring technique, through a network of six resonant PZT transducers. Besides classical methods of AE data analysis, including 3D AE source location and b-value analysis, the application of a recently proposed approach based on Natural Time (NT) analysis is herein proposed [1,2]. The present study focuses on identifying the entrance of the system into a critical condition, through the definition of a critical NT parameter, to be extracted from the AE signal time series, as a pre-failure indicator. The numerical simulation of this test using a version of the Discrete Element method [3,4] allowed to understand some aspect of the damage evolution in the specimen regions, close to the formation of the critical cracks, that led to the collapse.
 Varotsos PA, N.V. Sarlis NV and Skordas ES, 2011 Natural Time Analysis: The New View of Time (Springer, Berlin).
 Potirakis SM and Mastrogiannis D, Critical features revealed in acoustic and electromagnetic emissions during fracture experiments on LiF, 2017 Physica A 485, 11–22.
 Iturrioz I, Lacidogna G, Carpinteri A (2014). Acoustic emission detection in concrete specimens: Experimental analysis and lattice model simulations. International Journal of Damage Mechanics, 23: 327-358.
Iturrioz I, Birck G, Riera JD (2018) Numerical DEM simulation of the evolution of damage and AE preceding failure of structural components. Engineering Fracture Mechanics, doi.org/10.1016/j.engfracmech.2018.02.023.