212-ACD : Acoustic emission and related NDE techniques for crack detection and damage evaluation in concrete
Technical Committee 212-ACD
Deputy Chair: Prof. Tomoki SHIOTANI
Concrete structures could deteriorate due to heavy traffic loads, fatigue, chemical reactions, unpredictable disasters, and poor workmanship. Eventually, retrofit and rehabilitation of the structures are in heavy demand all over the world, although the concrete structures have long been referred to as maintenance-free. It results in the need for the development of advanced and effective inspection techniques prior to repair works. Acoustic emission (AE) and related NDE (nondestructive evaluation) techniques have been extensively studied for more than four decades. These are inspection techniques by means of detecting elastic waves due to cracking and damage accumulation.
Recently, research activities on these techniques are very active in a variety of laboratory studies as well as theoretical research on backgrounds and verification. Accordingly, several activities for the standardization are in progress. Focussing on crack detection and damage evaluation in concrete, prospective techniques are selected and evaluated on practicability and applicability. This could lead to recommendations in RILEM. Because the maintenance of concrete structures is one of serious problems in the 21st Century, these recommendations are in great demand at present.
Terms of reference
Based on the backgrounds above, AE and related NDE techniques for crack detection and damage evaluation are first reviewed. A state-of-the art report will be published. After classifying techniques into proper objectives for measurements, several round-robin tests are selected, including destructive tests. Test results of NDE will be compared with those of destructive tests and evaluated in terms of applicability, versatility, usefulness for practice. At the end of the term, some recommendations on the selected techniques will be written and proposed to RILEM. The committee period necessary is estimated at 5 years.
Detailed working programme
- Literature survey
The starting literature are the proceedings of the ACI Conventions, AEWG Meetings, a series of Progress in Acoustic Emission (Proceeedings of International AE Symposium), and a series of Proc. of Structural Faults and Repair. Subsequent literature will be collected by members of the TC.
- State-of-the-art report
The results of the literature survey will be compiled in a state-of-the-art report. The report will also contain the experience in situ and laboratory measurements carried out by members of the TC. The report will be continuously updated during the lifetime of the TC.
- Round robin testing
Round robin testing is useful to assess the capability of a test method. In the case of crack detection and damage evaluation in concrete, several techniques are prospective and commercially available. Some of techniques are selected by the members and round-robin tests will be conducted focussing the targets associated with crack detection and damage evaluation. In order to compared to the outcome from the AE and NDE tests, some of destructive tests will be conducted.
- Test evaluation
The tests will be evaluated with respect to the targets by the members. The experience during testing will be also evaluated and discussed. The aim is to select the most prospective method(s) for further detailing and development.
At the end of the evaluation and discussion of various round-robin tests, recommendations will be prepared for standardized testing techniques. The recommendations will be submitted for publication in Materials & Structures.
A workshop is planned for presentation of the TC´s work and of the test recommendation. It is hoped that other experts which were not member of the TC will contribute to the workshop. The RILEM rec-ommendation could then be completed and offered to CEN or ISO as a pre-standard.
The workshop should prepare proceedings, possibly as the special issue of Materials & Structures, which contain the scientific merit of the test methods, their principles and potential applications.
There is no direct link to previous RILEM TCs. However, a relation could be established to TC-189, because theoretical bases for crack detection and damage evaluation are closely associated witrh fracture mecahnics. In additrion, close working relations with ACI Committee 228 and JSCE Committee 326 are considered essential to develope new recommendations.
The following results are anticipated:
- state-of-the-art report
- RILEM recommendations for testing cracking and damage in concrete.
- Workshop proceedings, possible as a special issue of Materials & Structures.
Pre-standard to be submitted to ISO.
Group of users
Testing laboratories, industrialists (mainly producers of mineral binders, additions, admixtures), construction companies, universities.
Specific use of the results
The economic impact is expected by better control on maintenance of concrete structures. This is because many issues are reported on deteraioration and damage of the concrete structures. It is often stated that the 21st Century is the century of not construction but maintenance. In this regard, the proposed TC is in critical demand on the RILEM recommendations.