7.18
Non-destructive Tests for Concrete Strength
Non-destructive tests, such as the rebound hammer test and penetration resistance test, can be used to determine the strength of concrete in an existing structure.
The rebound hammer, also known as the Schmidt hammer, houses a spring-loaded mass.
The hammer is held perpendicular to an even concrete surface by pressing the plunger against it, causing the spring to extend, retracting the mass.
When released, the mass rebounds from the plunger. The extent of this rebound is then measured on a scale fixed to the hammer and is called the rebound number.
The higher the value of the rebound number, the harder the concrete surface, indicating high concrete strength.
The penetration resistance test, also known as the Windsor Probe test, uses a gunlike device equipped with a triangular template with three holes.
The template is placed on the concrete surface, and probes are shot into the concrete through each of the three holes using the device.
The average of each probe's penetration through the hole is measured; the lower the penetration of the probe, the higher the strength of the concrete.
The rebound hammer test, also known as the Schmidt hammer test, is a non-destructive technique for evaluating the hardness of concrete and, indirectly, the strength of concrete. It operates on the principle that the rebound of a spring-driven mass from a concrete surface correlates to the surface's hardness. The device comprises a mass within a tubular housing, a spring mechanism, and a plunger that strikes the concrete. Upon release, the energy imparted to the mass by the spring causes it to rebound, with the travel distance of the mass providing a rebound number. This number, however, is influenced by the presence of aggregates and voids beneath the surface and the angle of the hammer, making multiple readings necessary for accuracy.
On the other hand, the penetration resistance test, or Windsor Probe test, measures concrete strength by measuring the penetration depth of probes shot into the concrete. This test, which slightly damages the surface by creating small holes, is performed using a gunlike device that discharges the probes through three holes in a template affixed to the concrete. The depth of penetration is inversely related to concrete strength, with the average penetration of three probes providing the measure. This method is considered to yield a more accurate estimate of concrete strength than the rebound hammer as it assesses the material below the surface.
Non-destructive tests, such as the rebound hammer test and penetration resistance test, can be used to determine the strength of concrete in an existing structure.
The rebound hammer, also known as the Schmidt hammer, houses a spring-loaded mass.
The hammer is held perpendicular to an even concrete surface by pressing the plunger against it, causing the spring to extend, retracting the mass.
When released, the mass rebounds from the plunger. The extent of this rebound is then measured on a scale fixed to the hammer and is called the rebound number.
The higher the value of the rebound number, the harder the concrete surface, indicating high concrete strength.
The penetration resistance test, also known as the Windsor Probe test, uses a gunlike device equipped with a triangular template with three holes.
The template is placed on the concrete surface, and probes are shot into the concrete through each of the three holes using the device.
The average of each probe's penetration through the hole is measured; the lower the penetration of the probe, the higher the strength of the concrete.
- Rebound Hammer Test - A non-destructive method for evaluating concrete hardness and indirect strength.
- Penetration Resistance Test - Measures concrete strength by testing the penetration depth of probes.
- Concrete Hardness - Refers to the resistance of a concrete surface to penetration or scratching.
- Concrete Strength - The ability of the concrete mixture to resist forces or loads.
- Non-Destructive Testing - Testing methods that do not damage or destroy the material being tested.
- Define Rebound Hammer Test – Understand how it is used to test concrete (e.g., impact hammer test concrete).
- Contrast Hammer test vs Penetration resistance test – Discern key differences (e.g., destructive vs non-destructive testing).
- Explore Test Examples – Understand both test scenarios (e.g., Smith hammer test or Windsor probe test).
- Explain Measurement Process – Deep dive on how the rebound hammer and windsor probe tests work.
- Apply in Concrete Testing Context – Understand when to use each test effectively.
- What is rebound hammer test and how to measure concrete strength with it?
- What is penetration resistance test and how it's different from hammer test?
- How do you correctly perform a non-destructive test on concrete?
From Chapter 7:
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