Abstract
The availability of new self-sensing cement-based strain sensors allows the development of dense sensor networks for Structural Health Monitoring (SHM) of reinforced concrete structures. These sensors are fabricated by doping cement-matrix mterials with conductive fillers, such as Multi Walled Carbon Nanotubes (MWCNTs), and can be embedded into structural elements made of reinforced concrete prior to casting. The strain sensing principle is based on the multifunctional composites outputting a measurable change in their electrical properties when subjected to a deformation. Previous work by the authors was devoted to material fabrication, modeling and applications in SHM. In this paper, we investigate the behavior of several sensors fabricated with and without aggregates and with different MWCNT contents. The strain sensitivity of the sensors, in terms of fractional change in electrical resistivity for unit strain, as well as their linearity are investigated through experimental testing under both quasi-static and sine-sweep dynamic uni-axial compressive loadings. Moreover, the responses of the sensors when subjected to destructive compressive tests are evaluated. Overall, the presented results contribute to improving the scientific knowledge on the behavior of smart concrete sensors and to furthering their understanding for SHM applications.
Highlights
Most current local monitoring systems provide limited assessment of the actual integrity of the monitored structure.Innovative solutions such as piezoelectric composites [1,2], micro-electromechanical systems (MEMs) [3], or fiber optic strain sensors [4], offer alternative monitoring solutions hardlySensors 2018, 18, 831; doi:10.3390/s18030831 www.mdpi.com/journal/sensorsSensors 2018, 18, 831 scalable to large-scale infrastructures without incurring high costs and utilizing complex signal processing algorithms [5,6]
This paper presents an experimental study on the behavior of a set of cement-based strain sensors fabricated with and without aggregates and with different Multi Walled Carbon Nanotubes (MWCNTs) contents
Results show that the percolation threshold is identifiable at 1% MWCNT
Summary
Most current local monitoring systems (e.g., strain gauges, accelerometers, optical sensors, vibrating wire, etc.) provide limited assessment of the actual integrity of the monitored structure.Innovative solutions such as piezoelectric composites [1,2], micro-electromechanical systems (MEMs) [3], or fiber optic strain sensors [4], offer alternative monitoring solutions hardlySensors 2018, 18, 831; doi:10.3390/s18030831 www.mdpi.com/journal/sensorsSensors 2018, 18, 831 scalable to large-scale infrastructures without incurring high costs and utilizing complex signal processing algorithms [5,6]. Most current local monitoring systems (e.g., strain gauges, accelerometers, optical sensors, vibrating wire, etc.) provide limited assessment of the actual integrity of the monitored structure Innovative solutions such as piezoelectric composites [1,2], micro-electromechanical systems (MEMs) [3], or fiber optic strain sensors [4], offer alternative monitoring solutions hardly. The superior electrical and mechanical properties of nanoengineered powders, such as Carbon NanoTubes (CNTs) and nanofibers, have resulted in several demonstrations of conductive cementitious materials with excellent sensing capabilities [10,11,12,13,14,15] Such materials offer great promise for the monitoring of large-scale Reinforced. Some aspects concerning the electromechanical behavior of these sensors, including the static and dynamic response, as well as their behavior under large strains up to failure, still remain an open research issue
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