Study On The Compression Sensibility Of Smart Concrete And Its Structure

In this paper the compression sensibility of carbon fiber reinforced cement (CFRC) and its structure are studied on the basis of predecessors' research, the conducting mechanism and the influent factors of compression sensibility and stableness are analyzed , and the application of the compression sensibility of CFRC on engineering is explored.(1) Physical model of the strain-resistance effect of CFRC is proposed. The series model that resistance of CFRC is composed of carbon fiber resistance, cement paste resistance and contact resistance between carbon fiber and cement paste is proposed on the basis of theoretic analysis and experiment.(2) The compression sensibility of CFRC is discussed by means of d.c. resistance and a.c. impedance and capacity measuring technique . The result shows are as following, first, using a.c. impedance measurement to measure the compression sensibility of CFRC can eliminate the polarization effect at the electrode of CFRC specimen and the thermoelectric force of the electrode effectively; the thermo sensitive effect can be avoided by using little electric current, so the a.c. impedance is much more stable than d.c. resistance. And in addition, A.c. impedance includes resistance and capacity reactance, and this capacity and resistance are parallel connection, the simultaneous reduction of the capacity reactance and resistance will make a.c. impedance reduce more acutely, therefore the sensitivity measured by this way is improved much more. Second, when CFRC specimen is compressed, its capacity will change with the change of pressure, mostly because the relative dielectric constant changes with the change of pressure, so the compression sensibility of CFRC can also be reflected by capacity measurement , and the change of capacity with stress-strain is sensitive, and the data of measurement are stable.(3) The compression sensibility of CFRC is measured when the specimen is restrained around the periphery. The result shows that the sensitivity reduces when the specimen is restrained around the periphery, but the linearity is better, which provide the basis of the compression sensibility of CFRC on engineering practice.(4) The application of the compression sensibility of CFRC on structure is explored. According to the stress-strain condition at different parts, CFRC islaid selectively, not only the higher compression sensitivity can be attained, but also the interaction between compression sensibility and temperature sensibility of CFRC is divided.(5) Monitoring corrosion of rebars by compression sensitivity of CFRC. If the rebars are bundled uniformly by a layer of CFRC, the CFRC cylinder will be compressed internally and the electrical parameters of CFRC will change when the rebars corrode . There is connection between the corrosion expansion force and the corrosion rate of rebars ,the corrosion of rebars and its propagation process can be known by monitoring the change of resistance of CFRC, and corrosion of rebars can also be monitored on real time ,on line and undamaged with compression sensitivity of CFRC. Experimental results reveal that this way to monitor the rebars corrosion by bundling them with CFRC is effective and sensitive.