Use Of Rebound Hammer In Testing Concrete Strength
Rebound hammer as you may know is used for checking concrete strength. Rebound hammer is called Schmidt Hammer also to honor Ernst O. Schmidt, who invented it in 1950s. This test depends on a principle according to which how any elastic mass rebounds is dependent on hardness in a surface on which elastic mass gets impinged.
Importance of Rebound Hammer Test
These hammers help to judge concrete’s compressive strength and such tests are used to check whether any concrete mixture is as per defined standards. It could be catastrophic if any concrete mix is weaker than required and could lead to structural failures.
Therefore, such kind of quality check using rebound hammers is very important for construction companies to perform. NDT or non-destructive testing such as rebound hammer tests on samples are also economical for companies to undertake compared to destructive testing.
How Rebound Hammer Works?
At the time of test rebound hammer’s impact bolt hits concrete surface at a specified force and after such impact the hammer rebounds. Total rebound distance gets measured and recorded with the help of a sensor & shown on the display screen. We will now look at the steps to check concrete’s strength with the help of rebound hammer.
Checking Concrete’s Strength
- First of all the test surface is smoothened with the help of grinding stone.
- Some test impacts are performed using rebound hammer prior to final measurements that are evaluated.
- Checking is done to make sure that all the settings are in place.
- Keep the rebound hammer totally perpendicular to test surface and push test hammer towards the surface.
- The surface needs to be tested with about twelve impacts & the average used. Additionally, impact points need to be apart by around 25 mm.
- Check the test results.
Types of Rebound Hammer Tests
There are two basic types used in rebound hammer tests, the first is mechanical and the second is electronic rebound hammer.
- Mechanical Rebound Hammer: It measures how much mechanical travel completed by impact mass on rebound. Things affecting it include guide rod friction, scale’s drag pointer friction, gravitational pull and velocity between mechanical & unit parts.
- Electronic Rebound Hammer: This makes use of actual rebound coefficient which represents correct coefficient of physical rebound.
Thus we can clearly figure out that rebound hammer tests are quite important in knowing whether concrete mix used is as per standards or not. These are an integral part of NDT and help construction companies spend less as compared to destructive testing.