**Bartłomiej Sawicki 1,\*, Antoine Bassil 2,3, Eugen Brühwiler 1, Xavier Chapeleau <sup>2</sup> and Dominique Leduc <sup>4</sup>**


Received: 13 June 2020; Accepted: 7 July 2020; Published: 12 July 2020

**Abstract:** Following the significant improvement in their properties during the last decade, Distributed Fiber Optics sensing (DFOs) techniques are nowadays implemented for industrial use in the context of Structural Health Monitoring (SHM). While these techniques have formed an undeniable asset for the health monitoring of concrete structures, their performance should be validated for novel structural materials including Ultra High Performance Fiber Reinforced Cementitious composites (UHPFRC). In this study, a full scale UHPFRC beam was instrumented with DFOs, Digital Image Correlation (DIC) and extensometers. The performances of these three measurement techniques in terms of strain measurement as well as crack detection and localization are compared. A method for the measurement of opening and closing of localized fictitious cracks in UHPFRC using the Optical Backscattering Reflectometry (OBR) technique is verified. Moreover, the use of correct combination of DFO sensors allows precise detection of microcracks as well as monitoring of fictitious cracks' opening. The recommendations regarding use of various SHM methods for UHPFRC structures are given.

**Keywords:** crack detection; crack opening; distributed fiber optic sensors; DIC; UHPFRC; testing; SHM; microcracking
