Report rep040 : Non-Destructive Evaluation of the Penetrability and Thickness of the Concrete Cover - State-of-the-Art Report of RILEM Technical Committee 189-NEC

In the last 10 to 20 years considerable research efforts have been devoted to a better understanding of the deterioration processes that affect concrete constructions. In addition, the principles of sustainable construction and life cycle of buildings have increased the awareness of all players in the construction chain regarding the importance of durability, as a key design factor.

Despite the advances made, the standards and codes have remained, so far, basically prescriptive-oriented, although this may change in the near future.
An important step forward was made by RILEM TC 116-PCD Permeability of concrete as a criterion of its durability, chaired successively by Prof. H.K. Hilsdorf and by Prof. J. Kropp. The more tangible contribution of that TC was the publication of a State of the Art Report (RILEM Report 12) and a RILEM Recommendation for testing concrete in the laboratory for gas-permeability and for capillary water absorption, as well as for the preconditioning of the specimens prior to those tests.
The work of that committee, including a round-robin test, focused predominantly on laboratory tests, although site tests were also reviewed.
The other contribution of TC 116-PCD was the solid ground and inspiration it provided for the creation of RILEM TC 189-NEC Non-destructive evaluation of the concrete cover, which can rightly be considered as its successor.
Eight of the members of TC 116-PCD were also members of TC 189-NEC, including both chairmen, which gives testimony of a continued effort in the pursuit of new approaches towards the goal of performance-oriented ways of specifying and controlling the durability of concrete.

It is also important to mention that the work of the TC focused on concrete that is relatively young (up to a few months of age), as a contribution towards the goal of specifying and con-trolling the durability through the application of "in situ", performance oriented tests at rela-tively early ages. Nevertheless, many of the site methods presented in this report have proved useful for the condition assessment and monitoring of existing, aged structures.
After introducing the social and economic consequences of durability problems, the concept of ‘covercrete’ and the specification of durability, the report includes the following chapters: Transport mechanisms and reference tests / Non-destructive methods to measure gas-permeability / Non-destructive methods to measure water transport / Non-destructive methods to measure ion migration / Effect of moisture and temperature on non-destructive penetrability tests / Non-destructive assessment of the cover depth / Comparative test - Part I: "Penetrabil-ity" test methods / Comparative test - Part II: "Covermeters". The last part of the report gives the main findings and conclusions of the different chapters, overall conclusions of the work of RILEM TC 189-NEC, and proposals for further work

Contents

Chapter 1. Introduction and problem statement

Chapter 2. Transport mechanisms and reference tests

Chapter 3. Non-destructive methods to measure gas-permeability

Chapter 4. Non-destructive methods to measure water transport

Chapter 5. Non-destructive methods to measure ion migration

Chapter 6. Effects of moisture and temperature on non-destructive penetrability tests

Chapter 7. Transport mechanisms and reference tests

Chapter 8. Comparative test - Part I: "Penetrability" test methods

Chapter 9. Comparative test - Part II: "Covermeters"

Chapter 10. Conclusions and further work

Annex A

Annex B

Annex C