Sol-Gel Coating Membranes for Optical Fiber Sensors for Concrete Structures Monitoring

Abstract

The use of advanced sensing devices for concrete and reinforced concrete structures (RCS) is considered a rational approach for the assessment of repair options and scheduling of inspection and maintenance strategies. The immediate benefits are cost reduction and a reliable prevention of unpredictable events. The use of optical fiber sensors (OFS) for such purposes has increased considerably in the last few years due to their intrinsic advantages. In most of the OFS, the chemical transducer consists of immobilized chemical reagents placed in the sensing region of the optical sensor by direct deposition or by encapsulation in a polymeric matrix. The choice of the support matrix impacts directly on the performance of the OFS. In the last two decades, the development of OFS functionalized with organic–inorganic hybrid (OIH) sol–gel membranes have been reported. Sol–gel route is considered a simple method that offers several advantages when compared to traditional synthesis processes, allowing to obtain versatile materials with unique chemical and physical properties, and is particularly valuable in the design of OIH materials. This review will provide an update of the current state-of-the-art of the OFS based on OIH sol-gel materials for concrete and RCS since 2016 until mid-2021. The main achievements in the synthesis of OIH membranes for deposition on OFS will be discussed. The challenges and future directions in this field will also be considered, as well as the main limitations of OFS for RCS monitoring.

On the Use of Polymer-Based Composites for the Creation of Optical Sensors: A Review

“…There are many polar substituents that contribute to the formation of dipole interactions with the corresponding substrates. Such matrices include: among the organic ones most popular are oligo-polysaccharides [ 46 , 47 ], cellulose [ 48 , 49 , 50 , 51 ], polymethylmethacrylate (PMMA) [ 52 , 53 , 54 , 55 ], polyvinyl chloride (PVC) [ 11 , 56 ]; among inorganic ones most popular are silica and other polymeric oxides obtained by sol-gel synthesis [ 57 , 58 , 59 , 60 , 61 , 62 ]. On the other hand, the luminophore must have the following groups (one or several): H-, hydroxo-, amino-, nitro-, sulpho-, mercapto- and groups comprising from atoms with an unsplit electron pair and capable of forming a donor-acceptor bond; phenyl and other cyclically conjugated molecules to form π-π stacking.…”

Fiber Reinforced Polymer Debonding Failure Identification Using Smart Materials in Strengthened T-Shaped Reinforced Concrete Beams

“…Recently, the number of nondestructive approaches accessible for structural health monitoring (SHM) of EB-FRP strengthening systems has increased. Infrared thermography, ultrasonic wave velocity inspection, and X-ray inspection are some of the available SHM techniques [ 19 , 20 , 21 , 22 , 23 , 24 ].…”

Combination of fluorescent and spin labels: a powerful method for the optimization of hydrophilic membranes for the separation of oil-in-water emulsions

“…Oil droplets spread over the surface of such defects, making the material more hydrophobic and reducing its effectiveness in separating emulsions [15]. The characteristics of the gel on the surface of the fibres and its density and adhesion strength to the fibre, are also of great importance [16]. Therefore, methods that make it possible to determine the qualitative characteristics of the coating on the fibre are crucial in the manufacturing of hydrophilic membranes.…”