The Producing And Properties Studing Of Smart Carbon Fiber Concrete

Smart carbon fiber concrete (SCFC) is a kind of multifunctional concrete based composite material by uniformly admixing short carbon fibers to concrete and it not only has good mechanical characters but also possesses the sensing ability. This sensing capability can be used in health monitoring, damage accumulation and residual life forecasting to the concrete structure on service or subject to natural disaster.The following conclusions have been obtained in this thesis:(1) The principle, producing technique and the main factors which influence the conductive properties of the smart concrete are discussed. It is found that the dispersion of carbon fiber is the key problem of manufacturing SCFC. The content and the degree of dispersion of carbon fiber, the water/cement ratio, the sand/cement ratio and the curing age have obvious effects on the resistance of SCFC.(2) The piezoresistivities of SCFC under monotonic compressive loading, cyclic loading with increasing amplitudes, cyclic loading with constant amplitude and the dead loading are investigated. The experiment results reveal that the resistance changing of SCFC can reflect quantitatively the loading on it, so the SCFC can be used as compress strain sensor.(3) The change of resistance in SCFC beam under bending load is discussed.lt is found that the resistance decreases slightly with the increasing of the loading at the beginning, but when the loading increases to a certain value, the resistance changes sharply and then turn slowly again until the beam fracture. The change of the resistance indicates the formulation and the propagation of the micro-crack in the SCFC, so SCFC has the ability of self-diagnose.(4) The change of resistance in SCFC under fatigue compress loading is studied. At first, SCFC is pressed densely, its internal crack flaw is closed and as a result the resistance of SCFC decreases. The resistance value increases gradually with the number of the loading cycles. This phenomenon indicates that the damage occurres under the fatigue loading and the damage is accumulated during the fatigue process.(5) The thermoelectricity behavior and the properties of electrothermal effect of the SCFC are discussed preliminarily and the possibility of using this material in deicing system is evaluated shortly.