Title:
In-Place Bond Testing and Surface Preparation of Concrete
Author(s):
Kal R. Hindo
Publication:
Concrete International
Volume:
12
Issue:
4
Appears on pages(s):
46-48
Keywords:
bonding; concretes; hydrodemolition; microcracking; tests; pneumatic hammers; tensile strength; General
DOI:
Date:
4/1/1990
Abstract:
Our concrete infrastructure is experiencing rapid deterioration and is wearing out faster than it can be repaired or replaced. It is typically expensive to remove all of the old concrete and replace it with new. Accordingly, the most cost-effective and economical methods of repair have been removal of poor concrete and replacement with patches or overlay materials. The quality of the bond between the repair material and the existing concrete is critical to the success of the repair. The strength and quality of the bond of concrete have been problems for engineers. The variety of tests that have been utilized do not always represent in situ conditions, nor do they provide accurate evaluation of the strength and quality of bond. However, a new in-place bond test of concrete has been developed whereby in-place strength and quality can be assessed. This method measures direct tensile strength and permits the engineer to examine and evaluate the bonded surface and/or location of failure in the concrete. These bond tests can be performed at the site at any desired location to represent the work performed. The problem of developing good bond in concrete is influenced during preparation of the bonded surface by the effects of some removal techniques. Most available techniques leave the prepared surface with microcracks, resulting in a weakened plane that consequently affects the bonding of the two surfaces. However, hydrodemolition methods have demonstrated the ability to significantly increase bond strength by removing concrete without damaging the prepared bond interface.