Fracture monitoring of thermally damaged High-Strength Fiber-Reinforced Concrete by Acoustic Emission (Abstract-only)

CAGGIANO, A., ; XARGAY, H., ; MARTINELLI, E., ; FOLINO, P., ; KOENDERS, E.A.B; GÓMEZ, M.,

Conferencia; Materials Science and Engineering ? MSE 2018; 2018

Acoustic Emission (AE) method has demonstrated great potential and usefulness for Structural Health Monitoring (SHM) of concrete buildings. In order to consolidate this objective, it is necessary to expand the knowledge about the response of the AE to a wide range of actions that could affect concrete structures. In this matter, high temperatures are one of the most damaging actions for concrete and for what concerning AE technique there is a lack of studies about AEs applied for high temperature monitoring. In this work, an experimental campaign was perfomed on HSFRC under high temperature events. High-Strength Fiber-Reinforced Concrete (HSFRC) samples, subjected to 300ºC (HSFRC300) and 600°C (HSFRC600), were studied. Some reference specimens were kept in controlled laboratory conditions without thermal treatment (HSFRC20). Additionally, High-Strength Concrete (HSC) samples with equivalent matrix composition were prepared for comparatively studying the fibers bridging effects based on three-point bending test set-up by RILEM TC 162-TDF recommendation. These tests were also continuously monitored using a PAC AE system.HSFRC600 samples showed comparatively lower AEs at the beginning stage of the tests. The material was degraded generating multiple cracks during thermal treatment and therefore an important irreversible release of internal energy manifested as AE. Then, when testing the beams, such energy is no longer available. Moreover, pre-existing thermal cracks difficult the propagation of AE waves through the material, greatly increasing attenuation of signals. Taking into account that concrete service limit states design restricts crack openings to a maximum of 0.4 mm for environmental normal exposure, the amount of accumulated AE that can be related to concrete damage level, was significantly lower for HSFRC than for HSC. Thermal degradation in recorded AE features was evidenced. Macrocracks were developed from pre-existing thermal cracks, generating a smaller amount of AE events with smaller amplitude than in plain specimens. Fiber effectiveness restricting cracks propagation was observed by AE activity rate. AE has demonstrated to be strongly sensitive to concrete cracking process.The research activities here presented are developed within the framework of the SUPERCONCRETE Project (H2020-MSCA-RISE-2014 n 645704; http://www.superconcreteh2020.unisa.it/) funded by the European Union.