ABSTRACT
The most commonly employed methods of testing concrete for concrete repairs such as measuring compressive strength or cement content or pull-off testing for bond strength, leave many unanswered questions when it comes to assessing the condition of the concrete in a structure, or the overall effectiveness of a concrete repair. For example, the bond strengths measured by pull-off testing may be low but it is often not possible to determine why this is so without further testing. The measured cement content may be unexpectedly low, but it is not possible to determine without further testing whether or not the repair material contains a cement replacement material such as PFA that might affect the cement content measurement.The key questions that can be answered by petrographic examination in evaluating a concrete structure in need of repair are: • What is the current condition of the concrete?• Is the concrete undergoing on-going deterioration?• What depth of concrete needs to be removed before repair materials can be applied?
