Title:
Nondestructive Evaluation of Early-Age Concrete Strength
in Plate Structures by the Impact-Echo Method
Author(s):
Stephen Pessiki and Matthew R. Johnson
Publication:
Materials Journal
Volume:
93
Issue:
3
Appears on pages(s):
260-271
Keywords:
compressive strength; concretes; impact tests; nondestructive tests.
DOI:
10.14359/9811
Date:
5/1/1996
Abstract:
This paper 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 sur-face, 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. With the thickness of the test object known, the compression wave (P-wave) velocity is determined. A previously established concrete strength/P-wave velocity relationship is used to estimate in-place strength. Results indicate that the impact-echo method can be use to determine P-wave velocity and to estimate concrete strength in a large volume of early-age concrete such as the slab specimens tested in this study. Successful impact-echo tests can be made at very early ages when the concrete has low compressive strength, less than about 4.5 MPa (650 psi). Use of the impact-echo method to non-destructively estimate the in-place strength of concrete should be limited to the estimation of early-age strength.