Damage Evaluation in Freezing and Thawing Test of Concrete by Elastic-Wave Methods

In the freezing and thawing test of concrete, the frost damage is nondestructively evaluated by elastic-wave methods. In this regard, two alternative methods are recently proposed in RILEM recommendations. One is based on the ultrasonic test, which measures the transmission time of the longitudinal wave (P wave) and the other is associated with the resonant frequencies of vibrations. Re-examining formula to estimate dynamic moduli of elasticity in the standards available, evaluation of the frost damage by the elastic-wave methods is studied. Concerning the resonant frequencies of concrete samples, a three-dimensional analysis is performed by the boundary element method to identify actual vibrating-modes. It is clarified that an assumption of the one-dimensional resonant vibration is not applicable, because the assumption is responsible for a discrepancy between the dynamic and the static moduli. In order to evaluate the frost damage experimentally, the freezing and thawing tests were conducted by employing concrete samples after 1 year curing. The modulus of elasticity obtained from P-wave velocity is recommended to use as the durability factor, although homogeneous damages are only assumed in concrete samples. It is found that this modulus is comparable to the tangential modulus of elasticity in the compression test