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.

[1] Varotsos PA, N.V. Sarlis NV and Skordas ES, 2011 Natural Time Analysis: The New View of Time (Springer, Berlin).

[2] Potirakis SM and Mastrogiannis D, Critical features revealed in acoustic and electromagnetic emissions during fracture experiments on LiF, 2017 Physica A 485, 11–22.

[3] 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.

[4]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.