Research On Experimental Methods For Detecting Erosion Damage In Concrete

To improve the service life of engineer structures is the most effective method for energy saving and emission reduction. Therefore, the durability of concrete structures in the marine environment should be firstly considered when we design the structures. Most attentions are paid to scientific and reliable testing method to detect the attenuation laws of concrete's strength and stiffness by many scholars and engineering technology researchers.Sulfate erosion is the main reason to reduce the durability of concrete. The damage evolution and testing method are studied in this research.Firstly, the research progress and the erosion mechanism of concrete under the sulfate attack are summarized, and advantage and shortage of the existing non-destructive testing technology are analyzed. From this investigation, a foundation is established for finding new experimental technology to detect the damage evolution of concrete.Secondly, the damage evolution of concrete under sulfate attack is studied by accelerate experiment method. The expansion,the amplitude attenuation properties and the conductivity's variation of concrete in different aggressive solution is obtained by experiment. The relationships between the attenuation properties and damage, and between conductivity and damage is established by analyzed the experiment result, and a new experimental method to analysis damage of concrete in the aggressive environment is proposed.Thirdly, ultrasonic wave technique is used to detect amplitude along the length of the concrete specimens. According to detecting, the attenuation law of first wave with the detection distance is obtained in this research. So we can get attenuation coefficients by fitting experimental data. The constitutive relation of material is assumed to be Maxwell model, and Voigt model, and standard linear solid model, respectively. The propagated solutions are obtained in terms of variable-separated method. The governing equation on the propagation of expansion waves in a viscoelasticity material is derived theoretically,and the relaxation time is also obtained.In order to investigate the effect of Poisson's ratio on the attenuation of aitrosonic wave, two situations are considered. The first one is that the Poisson'ratio is assumed to be a constant, and the second one is that the Poisson's ratio is not a constant, but a function of damage. The results indicate that the Piosson's ratio of the material is not a sensitive parameter for attenuation of the viscoelastic wave. Therefore, the variation of Poisson'ratio cause by damage evolution of concrete in aggressive environment can be neglected.Finally, conclusions as well as advises on the further study are summarized.