Aged concrete strength and propagation velocity ratio of longitudinal and transverse wave: Fid-Bau Portal

Aged concrete strength and propagation velocity ratio of longitudinal and transverse wave

Kobori, O. / Taniguchi, Y. / Udagawa, Y. / Hirano, M.

There are about eighty thousand dangerous districts of landslides in Japan. We have constructed a great number of concrete earth holding dams for the purpose of disaster prevention. Most dams will be damaged over time by degradation, such as Alkali-aggregate reaction, salt, etc. Nondestructive dam inspection was done by the government. Many discussions have taken place to find the best solution to determine; where the damage is, how to strengthen and how to repair the dams economically versus new construction. Sampling cores from one of the aged dams were extracted at the fourteen spots on the sidewall of the dam. Ultrasonic wave was propagated to the core specimen and the velocity ratio of the longitudinal and transverse wave was calculated. After the development of Alkali-aggregate reaction in each core specimen was investigated, the compressive load was applied to these cores and failed. Conclusions are summarized as following. (1) Velocity ratio R between longitudinal and transverse is 1.80 in these concrete cores, and its average Poissons ratio ny = 0.27 . And the velocity in the damaged concrete is slower than that in goodconcrete. (2) Longitudinal and transverse velocity was 4300 m/s and 2400 m/s respectively in the model concretespecimen certificated that is strength at 18 N/mm2. Aged concretewould have been placed at the samestrength, and some of cores extracted from the aged dam are larger than model concrete in velocities andcompressive strength and some of them the similar velocity and strength. (3) From the nondestructive point of view at the aged dam, comparingthe standard model. Velocity and strengthat location D4, F2, G1 and G2 is larger than model and there is no need of repair now. Location B1, C1, D3and E2 is in the between health and damaged. They will be repaired in the future and A, B2, D2, E1 and F1has lower velocity and strength. They have to be repaired. (4) Numerical scoring method is proposed to the Alkali-aggregate reaction. It is also correlated to the velocityratio. Further investigation will be needed to find the numerical way of concrete degradation.