What Is a Rebound Hammer Test? The Function & How to Do It

Rebound hammer tests are one of the most popular testing methods in the civil construction industry. This technique is used to assess the strength and integrity of concrete structures without damaging them.

Using a special hammer-shaped tool, the tester strikes the concrete surface and measures the vibration response. This method is commonly applied to elements such as walls, floors, columns, and bridges to ensure the safety and durability of construction quality.

In addition to being practical and easy to use, rebound hammer tests also help save project budgets. Many cases of building damage occur due to improper concrete quality or structural miscalculations.

Therefore, it is important to conduct this test to reduce the risk and ensure the concrete grade before continuing the project. Check out the full explanation in this article, from the function, tools used, to the testing procedure.

What Is the Hammer Test?

Hammer test, also known as Schmidt Hammer or Rebound Hammer, is a non-destructive test method used to assess the quality of concrete after it has hardened. This test is conducted by bouncing a small hammer against the surface of the concrete and measuring the level of reflection.

It was invented in 1954 by Swiss engineer Ernst O. Schmidt and commercially developed by Antonio Brandestini, founder of the Proceq company, which is still the main manufacturer of this tool. Despite its simplicity, the hammer test is considered accurate and efficient because the process is fast, the tool is portable, affordable, and the results are reliable enough to assess the strength of concrete.

Hammer Test Functions

Hammer tests are not only used to test concrete surfaces, but also have several important functions in assessing the quality of the structure. Here are some of the main functions of a concrete hammer test that you need to know.

1. Knowing the Concrete Compressive Strength

The hammer test results can be converted to determine the concrete compressive strength. This value is important because it shows the capacity of the concrete to withstand loads. This way, you can ensure whether or not the existing concrete is following the design specifications.

2. Evaluating Concrete Quality

Hammer tests are used to evaluate the quality of hardened concrete. You do this by hammering a small hammer into the surface of the concrete and measuring the level of rebound. From these results, you can get an idea of the hardness and durability of the concrete.

3. Validating Concrete Uniformity

Hammer tests can be used to validate the uniformity of concrete throughout the structure. This makes it easier to identify potential weaknesses and ensure consistent construction quality.

4. Monitoring Concrete Durability

Periodic hammer tests play an important role in monitoring changes in concrete durability over time. These tests aim to ensure the viability of the structure and determine the right time to do repairs or renovations.

5. Detecting Concrete Problems

Hammer test results can also be used to detect weak or damaged concrete locations, such as those due to freezing, fire, or construction defects. These tests can be an early preventive measure and a proper renovation to prevent further structural failure.

Work Principle of Hammer Test

The hammer test works by delivering an impact using a bouncing hammer on the surface of the concrete. The mass inside the hammer is released with a certain energy and bounces back after hitting the concrete.

The harder the concrete, the greater energy is reflected and the higher the bounce value on the tool. This value is then correlated with the compressive strength of the concrete to assess its structural toughness.

In the test, the hammer should be pressed perpendicularly and slowly into the surface of the cleaned and flattened concrete. The measurement result is read from the scale on the tool after the hammer strikes the concrete. Usually, the test is carried out at several points with a minimum distance of 25 mm between points to obtain representative results.

Also, please note that the hammer test is only used to measure the surface hardness of concrete to a depth of about 4 cm, so the results are more of an initial indication of the quality of the concrete, especially in large dimension elements.

When Is a Hammer Test Used?

The hammer test is used when there is a need to test the integrity and strength of the concrete structure. Here are some conditions where the use of hammer tests is highly recommended:

During the construction phase, hammer tests are conducted to ensure the quality of the concrete meets the standards and reduce the risk of future structural failure.
Before using or maintenance, the test aims to ensure the safety of the structure and its ability to withstand the expected load.
When damage or leakage occurs, hammer tests help evaluate the extent and cause of the damage to plan appropriate repairs.
In older buildings, testing is used to detect signs of weakness or deterioration of concrete over time.
When renovating, hammer tests are conducted to understand the condition of the structure so that design plans and construction methods can be adjusted accordingly.

Tips for Accurate Hammer Test Results

Although it looks easy, the accuracy of the hammer test results is highly dependent on the correct execution technique. Here are tips to get valid results:

Use the right hammer: Choose a hammer according to the type of concrete to be tested. Make sure the hammer is in good condition, calibrated, and pay attention to the measurement scale and impact energy.
Prepare the concrete surface: Clean the concrete surface of any dust, dirt, or paint that could affect the reflection results. Make sure the surface is flat and free of large cracks. Avoid areas close to the reinforcement when conducting the test.
Choose a representative area: Perform the test at a location that shows similar concrete conditions. Avoid corners, edges, or joints of the concrete as they may produce inaccurate reflection values.
Do it correctly: Hold the hammer perpendicular to the concrete surface and apply a consistent force during each test. Record the rebound value that appears on the scale.
Do it repeatedly: To get a more reliable average value, conduct at least 5-10 tests at the same location. This will reduce measurement errors.
Use appropriate tables or conversion curves: Convert the average rebound value to an estimate of the concrete compressive strength using a conversion table or curve appropriate to the type of hammer and concrete conditions. Ensure that the table or curve is up-to-date and valid.
Consider other factors: Pay attention to factors such as age, moisture, and temperature of the concrete, as they can affect the results. If possible, conduct the test on concrete of a similar age and condition for a more valid comparison.

It is important to remember that the use of concrete hammer tests should be customized to the needs of the project and conducted by a civil engineer or trained team. In addition, following applicable standards and guidelines, as well as using the right equipment, is important to ensure accurate and valid test results.

That is a complete explanation of the concrete hammer test, from its definition, function, and how it is implemented. This test is very important to ensure that the concrete used in your project has the strength and quality according to the standard.

However, besides testing, the simplest and most effective step to ensure the quality of concrete is to choose a trusted concrete producer. In this case, Semen Merah Putih provides Precast Concrete and Ready Mix Concrete as a solution for your construction projects.

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