In-Place Evaluation of Concrete Strength Using the Impact-Echo Method


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Title: In-Place Evaluation of Concrete Strength Using the Impact-Echo Method

Author(s): S. Pessiki and M. R. Johnson

Publication: Special Publication

Volume: 143


Appears on pages(s): 275-296

Keywords: compressive strength; concretes; nondestructive tests; strength; ultrasonic tests; velocity; Structural Research

Date: 5/1/1994

Describes tests that were performed to evaluate the feasibility of using the impact-echo method to evaluate the in-place strength of concrete in plate-like elements such as slabs and walls. In the impact-echo method, a stress pulse is introduced into an object by mechanical impact on its surface, and this pulse undergoes multiple reflections (echoes) between opposite faces of the object. The surface displacement of the object, caused by the reflected pulse, is monitored at a location adjacent to the point of impact, and the frequency of successive arrivals is determined. Knowing the thickness of the test object, the compression wave (P-wave) velocity is determined. A previously established concrete strength-P-wave velocity relationship can be used to estimate in-place strength. Results indicate that the impact-echo method can be used to determine P-wave velocity through a large volume of early-age concrete such as the slab specimens tested in this study. Use of the impact-echo method to nondestructively estimate the in-place strength of concrete is more appropriately limited to the estimation of early-age strength.