CONCRETE TEST HAMMER

The Concrete Test Hammer, commonly known as the Schmidt Hammer or Rebound Hammer, is a non-destructive testing (NDT) tool used to assess the surface hardness and estimate the compressive strength of concrete in structures. It provides a quick and easy method to evaluate the condition of concrete without causing significant damage to the structure.

  1. Hammer Mechanism:
    • The main component is a spring-loaded hammer that strikes the concrete surface with a consistent force. The hammer’s rebound is measured and used to determine the concrete’s surface hardness.
  2. Rebound Scale:
    • The hammer’s rebound distance is measured on a graduated scale, typically marked on the side of the hammer. This rebound value is called the “rebound number” or “rebound index.”
  3. Housing:
    • The device is usually encased in a durable metal or plastic housing to protect the internal components and ensure accurate results.
  4. Plunger:
    • The end of the hammer has a plunger that is pressed against the concrete surface during testing. The plunger transfers the hammer’s impact to the concrete.
  5. Calibration:
    • Concrete test hammers are calibrated to ensure accurate readings. Calibration is usually done using reference test blocks made of materials with known properties.

The Concrete Test Hammer operates on the principle that the rebound of an elastic mass (the hammer) depends on the hardness of the surface it strikes. When the hammer is released, it impacts the concrete surface, and the plunger is pressed into the surface. The hammer then rebounds, and the distance of this rebound is measured. The rebound number is correlated with the surface hardness and can be used to estimate the concrete’s compressive strength.

  1. Preparation:
    • The concrete surface is cleaned to remove any loose particles or coatings that could affect the test results.
    • The hammer is then held perpendicular to the surface of the concrete.
  2. Test Execution:
    • The plunger is pressed against the concrete surface until the hammer is triggered and strikes the surface.
    • The rebound number is read directly from the scale on the hammer. Multiple readings are typically taken at different locations on the same surface to ensure accuracy.
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