NDT techniques for characterizing alkali-silica reaction in standard concrete specimens. A review: Fid-Bau Portal

NDT techniques for characterizing alkali-silica reaction in standard concrete specimens. A review

Chen, J. / Lesnicki, K.J. / Kurtis, K.E. / Kim, J.Y. / Jacobs, L.J.

Ultrasonic NDE techniques have been employed for the damage detection in cement-based materials for a long time. Most of the existing techniques are based on the measurement of a linear acoustic parameter such as pulse velocity, amplitude attenuation, or linear resonance frequency. However, these parameters are not sufficiently sensitive to the small scale damage in these materials such as ASR damage. This poor sensitivity comes from the fact that use of high frequency ultrasound with wavelengths smaller than the size of the largest aggregate is inherently limited due to the strong scattering in these materials. ASR is an important type of damage in cement-based materials and the capability of quantitatively evaluating this damage is presently of tremendous practical importance. For the characterization of ASR damage, numerous techniques have been developed that are based on the nonlinear acoustic and diffuse ultrasonic characteristics of the concrete materials. These nontraditional techniques not only show high sensitivity to ASR damage but also have some advantages in an instrumentation aspect. These techniques have been successfully applied to evaluate progressive microcracking due to ASR in standard mortar bar and concrete prism samples. The results show a clear distinction in reactivity levels of different aggregates. These techniques may be standardized as an alternative testing method to the existing ones after accumulating data for different aggregates. In conclusion, our past and current research indicates that the new NDE techniques based on nonlinear acoustics and diffuse ultrasound have a great potential for the damage detection in cement-based materials, especially for the in-field application which requires a better resolution due to the complex test conditions.