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Moisture Content Requirements for Effective Concrete Repairs

Project ID: 6629
Principal Investigator: Kurt Von Fay
Research Topic: Repair and Maintenance
Funded Fiscal Years: 2011, 2012 and 2013
Keywords: None

Project Abstract

Concrete repair and rehabilitation commonly involve removing unsound concrete before the placement of a repair material. Regardless of the quality of repair or overlay material used and application method employed, the care with which the concrete substrate is prepared and conditioned prior to application of repair material will often determine whether a repair project will be a success or a failure. The surface preparation for repair affects the strength and durability of the bond between the "old" and "new", between the existing concrete and repair material.
Surface preparation and moisture conditioning of the concrete substrate are generally considered to be two of the most influential steps in concrete repair works. A poorly prepared substrate will always be the weak link in a composite repair system, no matter how good the existing concrete and the repair material might be.
Concrete repair and bonded overlay are composite material systems. In such composites, the bond between the individual components is most critical for overall viability. The durability of the bond in repair or overlay systems can be defined as the lasting interfacial integrity of existing concrete and repair material. Of course, it is realized that high initial bond (short term) strength does not guarantee durability, but low initial bond may be a cause for debonding in service.
Therefore, assuming all properties of the substrate and repair material are adequate, any improvement of the bond will result in improved properties and long-term performance of the entire composite system.

Contributing Partners

None

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Moisture Content Requirements for Repair, Part 1: Concrete Repair Testing, Report No MERL-2013-63 (final, PDF, 1.0MB)
By Benoit Bissonnette, Kurt Von Fay and Alex Vaysburd
Report completed on December 03, 2014

Despite extensive use of surface repairs and overlays in rehabilitation of existing concrete structures over the last 25 years, failures are still often observed in practice. Irrespective of the methods selected, a fundamental requirement for successful repair is the achievement of strong and durable bond between the repair and the existing concrete substrate. Surface preparation and moisture conditioning of the concrete substrate are considered to be two of the most influential factors.
Keywords: concrete repair, surface preparation, bond testing

This information was last updated on December 18, 2014
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