Piezoresistive cement-based strain sensors and self-sensing concrete components

A type of embedded piezoresistive cement-based strain sensors (PCSS) is proposed for monitoring local compressive strain of concrete structures. A four-pole arrangement of embedded gauze electrode is used to eliminate the contact resistance between electrodes and piezoresistive cement-based material thereby improving the measuring accuracy of the output signal of PCSS. Both carbon fiber and carbon black are added into cement-based materials to improve the reproducibility of piezoresistivity in PCSS. A compensation circuit in PCSS is incorporated to reduce the effect of temperature and humidity on the output of PCSS. PCSS are embedded in concrete beams and columns to monitor the compressive strain of beams and columns under field conditions. Experimental results indicate that a sensitivity of 0.0138%/i1/4iμ, a resolution of 0.007 i1/4iμ, a linearity of 4.25%, a repeatability of 4.36% and a hysteresis of 3.63% can be achieved using the proposed PCSS. It is therefore concluded that the self-sensing concrete components embedded with PCSS can be used to monitor their compressive strain.