科研之友
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摘要
Pore structure is an important factor that determines concrete%26apos;s macroscopic performance, including strength, freezing-thaw susceptibility, and thermal and transport properties. Well-dispersed air voids protect concrete from destruction during freeze-thaw processes, as well as from thermal stresses, but at the cost of reducing its strength. Therefore, measuring the characteristics of air voids in concrete is important to assess its strength and durability. The development of technologies that can measure the air voids in concrete quickly, nondestructively and accurately are important for this reason. In this paper, a new ultrasonic technology was developed to measure the air void distribution in concrete. The theoretical basis of this technology is an advanced ultrasonic wave scattering model in complex structural materials. The model can account for the attenuation effects of multiple-sized air voids. The air voids are treated as elastic scatterers or cavities, two extreme conditions for their actual physical effects. The total attenuations are derived by superimposing the wave attenuation due to air void scatterers, coarse aggregates and the viscoelastic cement matrix. To validate this model, experiments were conducted to measure the wave attenuation curve in cement and concrete specimens. Inversion analyses were conducted to match the predicted ultrasonic wave attenuation against the measured attenuation. The inversion parameters were used to determine the air void distribution by assuming they follow a logarithmicnormal distribution, which obtained reasonable results.
- 出版日期2013-3
