IDENTIFICATION BY ACOUSTIC EMISSION OF DAMAGES IN REINFORCED CONCRETE DURING ACCELERATED CORROSION TEST

In the scientific literature there are several examples about the use of the Acoustic Emission (AF) techniques on reinforced concrete structures for corrosion related damage identification. However the application of the AL technique in the civil engineering still requires the overtaking of several problems related to structure complexity, material inhomogeneity and the high attenuation factor for high frequency acoustic waves in concrete, environmental noise. Relationship between AE signal parameters and failure processes that produce these signals have to be properly defined by means of signal analysis procedures, these however needs a reference AE signals database. The reference signals have to be identified in laboratory tests on samples, for which the dominant failure mechanism was under control. In the present work the preliminary results of an experimental research aimed to evaluate the influence of damage due to reinforcement corrosion on AE behaviour of different reinforced concrete beams was reported (Tab. 2). Corrosion of reinforcement were accelerated by applying an electrical density current ranging from 100 mu A/cm(2) to 200 mu A/cm(2). Samples were continuously monitored by means of 5 A E sensors (Fig, 2). After two weeks of accelerated corrosion condition the samples were tested by acoustic emission without current. Each sample was then gradually loaded, under AE monitoring, with three points bending machine, in order to evaluate its mechanical behaviour in comparison with the beams without corrosion damages (Fig, 3). AE data were treated by means of calm ratio analysis. From this analysis, we found that the low strength concrete samples treated with electric current showed the highest calm ratio values in the first and intermediate loading steps (Tab. 3). NOESIS classification of the AE signals was also performed by supervised method (Fig. 4).