Application of Distributed Optical Fiber Sensing Technology to the Detection and Monitoring of Internal Swelling Pathologies in Massive Concrete Blocks

Abstract

This paper presents an experimental application of Distributed Optical Fiber Sensors (DOFS) for the Structural Health Monitoring (SHM) of concrete structures affected by internal swelling pathologies. In the framework of a large research project aiming to assess the possible extension of the operating lifetime of nuclear power plants from 40 to 60 years, massive blocks were cast from reactive concrete mixtures intended to develop delayed ettringite formation and alkali–silica reaction. These blocks were subjected to specific ageing conditions to initiate and accelerate the concrete pathologies. Some of the blocks were instrumented with DOFS bonded to the surface and embedded in the concrete. Using an interrogator device based on Rayleigh backscattering and a suitable procedure to eliminate temperature effects, distributed strain measurements were then performed at different time intervals. The first results of this ongoing study made it possible to demonstrate the feasibility and effectiveness of this sensing technology for detecting and monitoring expansion induced by swelling pathologies in representative-scale concrete structures.

Assessing and Forecasting ISR-Affected Critical Infrastructure: State-of-the-Art and Challenges

“…Although these techniques have been used to support the diagnosis of ISR-affected concrete, their accuracy and precision have proven to be higher in monitoring the escalation of ISR distress over time. Furthermore, these outcomes can be combined with sensors measuring displacement, humidity, and temperature and significantly improve ISR-damaged structures monitoring, such as fiber optic (local and distributed), vibrant wires, and strain gauges to measure strain; thermocouples to quantify temperature variation; and magnetic microwire embedded in cement-based composite (MMCC) to assess the stress/strain sensing properties of a cement-based material [ 48 , 49 , 50 ].…”

A Compact Source for a DAS without Trace Averaging based on a Low Phase Noise DDS and Mini-EYDFA

“…ISTIBUTED fiber optic sensors (DOFS) are becoming ubiquitous tools in many safety and integrity monitoring systems employed in various applications including the measurement of deformation [1], [2], [3], structural health monitoring (SHM) of concrete structures affected by internal swelling pathologies [4], and temperature monitoring [5]. Specifically, distributed vibrational frequency analysis is commonly used to detect spectral signatures of anomalies that necessitate pre-warning of infrastructure and device damages.…”

Crack Shape Coefficient: Comparison between Different DFOS Tools Embedded for Crack Monitoring in Concrete

“…This is the most convenient way and, at the same time, the most favourable in terms of interpretation. The benefits include: The possibility of analysis of the structural behaviour from a real zero stress–strain state through all the important phases [ 46 ], such as early-age concrete [ 47 ], thermal-shrinkage strains and corresponding micro-cracks [ 48 ], prestressing [ 49 ], construction stages, load tests [ 17 ], and, finally, regular operation. Structural assessment can be performed based on the absolute values of measured parameters (strains or crack widths) instead of their changes (increments).…”