Study On Smart Property Of Fiber Cement-based Composite Sensors Subjected To Bending

Structural health monitoring (SHM) is becoming an important tool to ensure the safety of concrete structures. Now the traditional sensors of health monitoring for concrete structures contain electric-resistance strain gauges, piezoelectric ceramic, optical fiber sensors, shape memory alloy, etc. But there are a lot of problems when these sensors are used in civil engineering. Recently, a new kind of self-sensing fiber cement-based composite materials (FCCM) gets wide attention and research. This paper mainly studied a new kind of fiber cement-based composite sensor (FCCS) that made of this fiber cement-based composite materials. The self-sensing ability of FCCS has been well demonstrated under tension and under compression (only in the elastic regime). However, its demonstration under flexure has not been well carried out, especially in the plastic failure region of FCCS. This paper focused on the smart property of a free FCCS and of reinforced concrete beams embedded FCCS. The studies are as follows:(1) The effects of sole admixture with carbon fiber, disphasic conductive admixture with carbon fiber and nano-carbon black triphsic conductive admixture with carbon fiber, nano-carbon black and steel fiber on the smart property of FCCS subjected to bending were investigated. The results showed that the load-bearing capacity of FCCS decreased suddenly, and the fractional change in resistance (FCR) also increased rapidly when upon reaching the cracking load. This showed a good mechano-electric effect of FCCS.(2) The FCR of FCCS increased with the increasing of crack opening displacement (COD) and the relationship between the fractional change in resistance and the COD was strong linearly correlated. The intercept of the fitting line said the magnitude of the bearing capacity decrease of FCCS and the slope defined the sensitivity of the measurement.(3) The FCR of FCCS increased with the increasing of the strain and the deflection of FCCS. The two relationships can be linearly fitted and the results were very good.(4) The FCR of the FCCS that embedded in the beam increased with the increasing of the strain at the bottom, the COD and the mid-span deflection of the beam. These three relationships can be linearly fitted and the results were very good. (5) Overall, we can monitor the strain at the bottom of a beam, the COD of a beam and the deflection of the mid-span deflection of a beam via the FCR of the FCCS that embedded in the beam.