Monitoring of crack propagation in fiber reinforced concretes: comparison of non-destructive techniques

This study was carried out for the French National Radioactive Waste Management Agency (Andra) as part of the Cigo project, a deep geological disposal facility for radioactive waste.Cigo consists of a network of concrete galleries where the radioactive wastes will be disposed.After the construction and operation phase, the galleries will be sealed, and no further human intervention will be possible.Therefore, to monitor the health of the galleries remotely, structural health monitoring (SHM) techniques are required.The study focused on using three different monitoring techniques, namely acoustic emission (AE), strain measurements using optical fibers, and electrical measurements with embedded sensors to test the self-sensing ability of the concrete.The objective was to cross-reference data from these various techniques to propose methods for detecting cracks in concrete elements.The obtained results were compared with those from digital image correlation (DIC).These tests were carried out on structural elements, i.e. beams subjected to 4-point bending test.With the dual aim of improving the relevance of these monitoring techniques and better controlling crack propagation, fibers were incorporated into the concrete mixes.Two types of fibers were used: amorphous metallic fibers (AMF) and carbon fibers (CF).The results showed that CF primarily enhanced crack detection through electrical measurements without significant influence on mechanical performance.However, AMF demonstrated their ability to restrain crack propagation and improved the relevance of electrical and AE measurements to monitor crack initiation and propagation.