As corrosion has slow development, its detection at an early age could be an alternative for reducing costs of structural rehabilitation. Therefore, the employment of structural health monitoring (SHM) systems, sensing configurations collecting data over time allowing for observing changes in the properties of the materials and damage emergence, for monitoring corrosion can be a good strategy to measure the damage and to decide the better moment for intervention. Nonetheless, the current corrosion sensor technology and the high costs of the sensing system implementation are limiting this application in the field. In this work, an optical fiber Bragg grating (FBG)-based sensing system is proposed for monitoring the thickness loss of a 1020 carbon steel metal plate subjected to controlled corrosion. The natural frequency of the plate was collected as a function of the corrosion time over 3744 h. To validate the experimental results, ultrasound measures and electrochemical tests were also carried out under similar conditions. The experimental results show adequate reliability, indicating the suitable functionality of the proposed system for monitoring the thickness loss caused by corrosion in metallic structures, in comparison with traditional methods, as ultrasonic and electrochemical measures.

Pipelines are structures with great relevance in different industrial sectors and are essential for the proper functioning of the logistics that support today’s society. Due to their characteristics, locations, and continuous operation, allied with the huge network of pipelines across the world, they require specialized labor, maintenance, and adequate sensing systems to access their proper operation and detect any damage they may suffer throughout their service life. In this work, a fiber Bragg grating (FBG)-based optical fiber accelerometer (OFA), which was designed and calibrated to operate through wavelength and optical power variations using different interrogation setups, was fixed together with a pair of FBG arrays along a 1020 carbon steel pipeline section with the objective of monitoring the pipeline natural frequency (f_{n_pipeline}) to indirectly evaluate the detection and evolution of corrosion when this structure was buried in sand. Here, corrosion was induced in a small area of the pipeline for 164 days, and the OFA was able to detect a maximum f_{n_pipeline} variation of 3.8 Hz in that period. On the other hand, the attached FBGs showed a limited performance once they could successfully operate when the pipeline was unburied, but presented operational limitations when the pipeline was buried in sand. This was due to the inability of the structure to vibrate long enough under these conditions and obtained data from these sensors were insufficient to obtain the f_{n_pipeline}.

The current work aimed to study nanomodified HPC with multi-walled carbon nanotubes (MWCNT). The effect of MWCNT concentration, from 0% to 0.6% of cement weight, was evaluated on HPC multi-level output properties, namely, the flowability, mechanical strength, electrical resistivity, and microstructure. In addition, a tentative, simplified, and more cost-effective method based on dispersion of a high-pH solution of hydroxide was also adapted to disperse the MWCNT before incorporation in fresh HPC mixtures. Adding 0.2–0.6% MWCNT reduced HPC workability even with a higher superplasticiser dosage. The electrical resistivity was 484.58 Ω m for the HPC without MWCNT at 28 days of curing, while the samples with 0.2%, 0.4%, and 0.6% MWCNT presented 341.41 Ω m, 363.44 Ω m, and 360.34 Ω m, respectively. The use of 0.2–0.6% MWCNT in HPC decreased the flexural and compressive strength by 20% and 30%, respectively. The HPC performance decrease with MWCNT seemed to be related to relatively significant agglomerations of the long MWCNTs, namely, in HPC-0.6% samples. New developments are needed to state a simple and cost-effective dispersion method for MWCNT incorporation in HPC. In addition, smaller dosages of MWCNT are suggested for future research works.