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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.

Nowadays, any structure must have strength, robustness and lightness, which has increased the industrial interest and research efforts in adhesive joining, mainly in the improvement of strength and fracture properties of adhesives. Thus, in recent years, the use of adhesive joints in industrial applications has gradually grown, replacing some traditional bonding methods, since they have advantages such as reduced stress concentrations, reduced weight and cost, and ease of processing/manufacturing. In this work, the cohesive laws of three adhesives, Araldite ® AV138, Araldite ® 2015 and Sikaforce ® 7752, were obtained by the application of an inverse adjustment method between the numerical and experimental load-displacement curves (P-) of Double-Cantilever Beam (DCB) tests for tensile characterization and End-Notched Flexure (ENF) tests for shear characterization. Next, these laws were validated with experimental data of single-lap joints (SLJ) and double-lap joints (DLJ), using Abaqus ®. For the Araldite ® AV138 and Araldite ® 2015, in tension and shear, the triangular law accurately predicted the behaviour of the SLJ and DLJ. For the Sikaforce ® 7752, the triangular law did not suitably fit the experimental results. Due to its ductility, the Sikaforce ® 7752 could be modelled with a trapezoidal law for improved accuracy.

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