The nondestructive impact-echo (IE) method offers a simple means for introducing compressional stress waves into a concrete element or slab and measuring the resonance frequencies associated with the reflections of the waves from any internal voids and the bottom of the slab. It is relatively effective for detecting internal voids or delaminations in concrete, which is the application for which it was developed. It may also be possible to use the method for indirect measurement of the thickness of a slab if the wave propagation velocity in the concrete is known. This study was conducted to determine whether the IE method, by itself, could replace the use of coring for quality-assurance measurements of the thickness of concrete slabs in newly built pavements. The results from tests conducted on three pavemems indicated that the wave velocity varied so much, not only between pavements but also within a pavement, that unacceptable errors can result when an average velocity is determined (through limited coring) for a pavemem and subsequently assumed for the entire pavement. To reduce the error to an acceptable level, the wave velocity at any test location must be measured to within an acceptable accuracy by another independent method. In pursuit of this approach, an indirect-transmission procedure based on ultrasonic (UT) measurement was incorporated and tested. This combined IE/UT procedure was able to measure thickness with absolute errors of 5 mm in one pavement and 7 mm in another, at a 90% probability. These results can be considered encouraging since the current procedure requires that the length of a core reported to the nearest 3 mm be the average of several measurements around the core and, in some cores, these measurements can have a spread of as much as 13 mm. In addition, it is expected that these errors can be reduced easily with the use of a transducer with a smaller contact face that would be less sensitive to roughness on the surface of grooved concrete pavements.

Civil engineers will value this resource that examines the tools and techniques used to estimate the in-place strength on concrete, permeation properties that relate to potential durability, and the methods used to assess the internal condition of concrete and the corrosion activity of steel reinforcement.

This book is a collection of papers presented in the NDT Conference held on February 20-23, 1996 at San Diego, California. The conference provided an opportunity to share experience and provide additional input to the Federal Highway Administration.

The Concrete Construction Engineering Handbook, Second Edition provides in depth coverage of concrete construction engineering and technology. It features state-of-the-art discussions on what design engineers and constructors need to know about concrete, focusing on - The latest advances in engineered concrete materials Reinforced concrete construction Specialized construction techniques Design recommendations for high performance With the newly revised edition of this essential handbook, designers, constructors, educators, and field personnel will learn how to produce the best and most durably engineered constructed facilities.

This series provides a comprehensive review of the latest research results in quantitative nondestructive evaluation (NDE). Part A of Volume 21 details the development of nondestructive evaluation techniques. Part B addresses advances in materials characterization, new applications, and reliability.