Multifunctional Cement Composites Strain and Damage Sensors Applied on Reinforced Concrete (RC) Structural Elements

Abstract

In this research, strain-sensing and damage-sensing functional properties of cement composites have been studied on a conventional reinforced concrete (RC) beam. Carbon nanofiber (CNFCC) and fiber (CFCC) cement composites were used as sensors on a 4 m long RC beam. Different casting conditions (in situ or attached), service location (under tension or compression) and electrical contacts (embedded or superficial) were compared. Both CNFCC and CFCC were suitable as strain sensors in reversible (elastic) sensing condition testing. CNFCC showed higher sensitivities (gage factor up to 191.8), while CFCC only reached gage factors values of 178.9 (tension) or 49.5 (compression). Furthermore, damage-sensing tests were run, increasing the applied load progressively up to the RC beam failure. In these conditions, CNFCC sensors were also strain sensitive, but no damage sensing mechanism was detected for the strain levels achieved during the tests. Hence, these cement composites could act as strain sensors, even for severe damaged structures near to their collapse.

Strain and damage sensing properties on multifunctional cement composites with CNF admixture

“…Strain-sensing [3][4][26][27][28][29][30] and damage sensing [27,[30][31][32] properties of carbon fiber reinforced cement composites have been vastly studied. Nonetheless, the addition of nano-admixtures has been vaguely reported, and in the last years it has been focused on CNT indeed [33,34].…”

Performance of cement-based sensors with CNT for strain sensing

“…Pastes were fabricated in laboratory conditions: 20°C temperature and 65% relative humidity (RH). This dispersion method has been used successfully in CNF cement composites (Baeza et al, 2013b;Galao et al, 2012 Performance of cement-based sensors with CNT for strain sensing Camacho-Ballesta, Zornoza and Garcés…”

Applications of Self-Sensing Concrete

“…Saafi embedded single-walled carbon nanotube cement paste into the tensile region of concrete beams to set up self-sensing concrete structures subjected to monotonic and cyclic bending (as shown in Figures 7.33 and 7.34) [28]. The self-sensing concrete [18]. They observed that self-sensing concrete with carbon fiber or carbon nanofiber is capable of measuring strains on the surface of a structural element, regardless of whether the local stresses were tension or compression.…”

“…The internal damage of the beams could be monitored by measuring the variation in electrical resistance of the graphite slurry infiltrated steel fiber concrete coating. Wang [18]. They observed that self-sensing concrete with carbon fiber or carbon nanofiber was capable of acting as a strain sensor attached to a reinforced concrete beam, even if the structure was close …”