Use CFRC's Functional Performance To Monitoring The Damage In Concrete Stucture

As the entrance of 21 centuries, the humankind set higher and higher requirements on the long-time monitoring of the safety of the grand projects. The projects without the long-time detection and monitoring on safety wouldn't be accepted by people. The behavior of damage accumulations and calamity in large-scale structures and infrastructures ,such as, bridges, skyscraper, long - span dimensional structures, big dams ,nuclear power plant, oceanic oil extraction flats, port establishments .etc, become more serious.Concrete is the most applied structural materials in civil engineering. Besides the influence of the exoteric loads, the concrete structures are confronted with the three big problem, such as the rust of reinforcing steel bar, the damage caused by freezing, and environmental corrosion.However the lifeblood of the projects' structures can reach scores of years, even to one hundred year. The coupling effects of the factors caused by calamity which conclude the load's fatigue effect environmental corrosion, and material aging, would unavoidably result in the damage accumulations and attenuation of resistance, and therefore would decrease the ability to resist natural calamity, and even can cause the disastrous sudden accident .So the monitoring of the grand civil engineering structures and infrastructures have become the important research subjects in the field of civil engineering.Carbon Fiber in carbon fiber reinforced Concrete can hugely improve the properties of conduction of the concrete. CFRC has the better mechanical properties, freeze-thaw resistance and low drying shrinkage than common concrete. CFRC possess some functional performances which concludes pressure-sensitive property, temperature-sensitive property, thermoelectric effect, mechanical-electric effect, and so on.When damage occurs in CFRC, the electrical resistance will change. AT the same time microscopic crack appears in cement paste, Carbon Fibers break and the decrease in the contact between the short carbon fiber and cement occurs, which make the resistance increase irrevocably.By using the damage response to the electric resistance of CFRC, we can detectthe growth and development of the damage in the concrete.The main research achievements of the present paper are listed as follow:1. Detection to local damage in concrete has been done, we examine the damage under three conditions that concludes compression ,cyclic compression and creep; use the change of electrical resistance and the infrared thermography to check the damage to analyze the inhomogeneity of components' compressive deformation, and compare the results with that of strain gauge measurement. The results show, using the electrical conductivity of CFRC can expand the means to detect the local damage in materials, and using the change of electrical conductivity and the infrared thermography to check the damage can protect the sample from being damaged, and the method is intuitionistic and high-accuracy. It is a new method to detect the concrete structures. Simultaneity, according to the situation that unhomogeneity of strain exists in the uniaxial compression of concrete components, we can point out the relationship between the gage length of stress and materials' rigidity, strain gradient and damage. The data offer basis for accurately test the basic mechanical property of the materials such as, rocks, concretes and so on.2. Forecast of the relic life-span of concrete is carried out. there exist some certain coincidence relation between in the change of CFRC's electrical resistance, during the service process of the concrete component ,the accumulation of damage can induce that the electrical resistance increase irrevocably. By using the theoretical analysis and experiments discussion, it is viable that monitoring the change of he electrical resistance can forecast the relic life-span of the concrete.3. Research about damage in freeze-thaw is done. By the examination to test block of CFRC under different freeze-thaws, we study the developing process of the test block in freeze-thaw, analyze the mechanism how the damage of concrete sample occurs, and supply some basis for the research of the freeze-thaw durability of concrete. The results turn out that, under the condition of freeze-thaw, the damage of the concrete is mainly resulted from the difference in temperature which happens inside the concrete. During the process of snow melting, we study how long-time energizing affect the structure of concrete ,and find out the threshold value of energizing, which can reduce the deterioration to concrete's service condition duringthe process of energizing 04. we estimate the concrete structures quality of repair. This paper use the carbon fiber reinforced cement and carbon fiber mat as the patching material ,and according to the change of the electrical resistance of patching material, we judge the combination compactness between the patching material and non-repair concrete structures, and then estimate the efficiency of patching. What's more, we use the infrared thermography to check the damage to analyze the quality of contact of two parts. It shows that, the change of electrical resistance can reflect the situation of contact in the surface between new and old concretes.The research achievement of this paper offers some new approach to use CFRC's functional performance to monitoring the damage in concrete structures, and is in favor of the development of intelligent concretes.