A study on microcrack monitoring in concrete: discrete element method simulations of acoustic emission for non-destructive diagnostics

The research is focused on the monitoring of fracture evolution in concrete beams under three-point bending using the acoustic emission technique and the discrete element method. The main objective of the study was to numerically and experimentally investigate the mechanism behind the generation of elastic waves during acoustic emission events and their interaction with micro- and macro-cracking in concrete beams under monotonic quasi-static loading. This was achieved through the development of a DEM model and numerical modelling of AE effects. An improved 4-phase DEM model of concrete including real mesostructured specimens and the ability to simulate aggregate breakage was introduced. The propagation of elastic waves, recorded in both laboratory experiments and numerical calculations, was given particular attention. The results showed the high suitability of the developed DEM model for monitoring crack initiation, development and propagation, as well as for supporting the interpretation of diagnostic results obtained by acoustic emission techniques.