Specifying concrete repair

Prescriptive or performance?
Specifications can be either prescriptive- or performance-based—there are many discussions underway regarding which better serves the intended purpose. Theoretically, the performance concept is ideal. However, considering the status of the concrete repair industry, it can be unsuitable because of the inadequate knowledge of those involved and the lack of evaluative techniques for some aspects of performance, especially in terms of the durability. Simply put, performance can be specified by way of satisfying a particular test. Some attempts to develop performance tests in the concrete repair field are now underway, but their practical reliability has yet to be determined and their application has still not been implemented.

With respect to the performance of repair materials, the situation is somewhat improved in that at least certain characteristics can be ensured. Nevertheless, many other behavioural repair characteristics, such as electrochemical activities, are largely unknown and difficult to predict. Caution needs to be exercised in establishing performance requirements, especially for repairing corrosion-related damage on structures subject to chlorides and marine environments. The performance approach may be applicable where the potential future performance is understood. However, this remains a challenge for repaired structures, as there is no proven link between lab-based performance test methods and actual in-situ performance.

Each issue, step, and requirement must be specified and controlled as performed. The actual myth of performance specifications for concrete repair projects might have risen from the assumption the contractor knows more about the achievement of durability than the engineer. Detailed guide specifications are needed in which the engineer, contractor, and inspector are given guidance in not only the ‘how,’ but also the ‘why.’ This allows for a real analysis of the situation and, ultimately, for a suitable decision to be made on how to proceed. The contractor should also be given direction concerning materials, methods, and equipment to be employed, unless he or she can demonstrate equal or better results by other means.

Conclusion
The engineering community involved in the design and implementation of concrete repair projects must recognize and accept the fact the specification documentation is not a formality, but rather a critically important engineering guideline to fulfil durability requirements. Specification writing is a complex task requiring extensive knowledge of science, engineering, and in-situ practice. It also entails a considerable standard of responsibility on the part of the professional working with it.

Engineers have become accustomed to accepting heavy responsibilities. According to the Babylonians’ ancient Code of Hammurabi, if a builder made a house and the house collapsed and caused the death of its owner, the builder was put to death. While the authors would not propose quite so harsh a measure for premature failure of a repair, they would nonetheless assert the industry must accept the responsibility for its shortcomings and strive forward to improve concrete repair projects.

Alexander M. Vaysburd, FACI, is the principal of Vaycon Consulting, a Baltimore, Md.-based firm specializing in concrete and concrete repair technology. He is a Fellow of the American Concrete Institute (ACI) and a member of various ACI and International Concrete Repair Institute (ICRI) committees. Vaysburd also serves as an associate professor at Laval University in Québec City. He can be contacted via e-mail at avaysburd@structural.net.

Benoît Bissonnette, FACI, is a professor in the department of civil engineering at Laval University, and a member of the Research Centre on Concrete Infrastructure (CRIB). A Fellow of ACI, he is part of various ACI, ICRI, and International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) technical committees. Bissonnette can be reached at benoit.bissonnette@gci.ulaval.ca.