Rebound Hammer Tests for Concrete Structures, commonly known as Schmidt hammer tests.
Rebound Hammer Testing is a simple and rapid technique commonly used to determine the uniformity of concrete in structures and to approximately estimate compressive strength.
It can be used in situations where concrete structures are suspected to be of inferior strength or as a rapid means to determine locations which may need to be investigated in further detail. It can also be used as a standard quality control check on building projects to ensure that the concrete quality being placed on large projects is consistent and meeting minimum strength requirements.
In situations when concrete is not properly designed or when the production process is inadequately controlled, flaws and defects may arise. These flaws can affect performance and reduce strength or durability. It is important to detect and assess their importance as early as possible. Rebound hammer testing is one of the main nondestructive testing (NDT) techniques capable of detecting, locating, and quickly alerting project staff of variations and inconsistencies in concrete structures.
The underlying principle of the rebound hammer test is measuring the rebound of an elastic mass on the surface against which its mass strikes. The rebound varies depending on the hardness of the surface.
The rebound hammer can be used to estimate in-place concrete strength by developing a correlation chart for the particular type of concrete used to construct the project or less accurately by comparison to standard published correlation charts.
The typical uses of rebound hammer testing on construction projects include:
- Determine in-place uniformity of concrete
- To locate variations in concrete quality throughout a structure
- Estimate in-situ strength if a correlation is available