Do you know about Rebound Hammer? Today in this post I am going to discuss such an instrument that can detect the hardness of any RCC structure. It is a machine that is not filed in engineering and construction.
Today we will try to know about this machine in particular. Have you seen this machine? See the figure above. What is this machine, and what is its principle, I will give details about the testing procedure.
Let’s start today’s special topic:
- To find out the compressive strength of the concrete structure.
- To get information on the uniformity of concrete
- To Check the quality of the concrete based on the standard specifications
- To relate one concrete element with another with existing Concrete quality
What is Rebound Hammer?
A rebound hammer is a tool used to check the hardness of the surface of concrete and other building materials. When an impactor mass strikes the surface of the material being tested, the rebound is measured.
After that, the rebound is transformed into a hardness value that can be used to gauge the material’s strength.
This is a non-destructive testing device, which means it won’t harm the substance being examined. It is frequently used in the building sector to assess the durability of concrete constructions like roads, bridges, and buildings. It is also applied to the upkeep of these buildings to look for deterioration or damage that might have developed over time.
It has come in a variety of varieties, but they all measure rebound according to the same general principles. The condition of the surface being tested, the age and quality of the hammer, and the operator’s skill are just a few of the variables that affect the rebound hammer’s accuracy.
Principle of Rebound Hammer?
The relationship between an elastic mass’s ability to rebound and a material’s hardness forms the foundation of the rebound hammer’s operating theory. The mass of the rebound hammer’s plunger is momentarily compressed against a spring when it strikes the surface of the material being tested. The plunger then returns to the material’s surface as the spring recoils.
A graduated scale on the rebound hammer measures the plunger’s rebound distance from the surface. The surface hardness of the material being tested is inversely correlated with the rebound distance. The plunger will rebound less from a harder surface, resulting in a lower number on the scale.
Utilizing a steel calibration anvil with a known hardness, the rebound hammer is calibrated. The correlation between the rebound distance and the surface hardness of the material being tested is calculated using the anvil’s hardness value. The surface hardness of the material can be calculated by comparing the rebound value from the test with the calibration chart.
What is the Rebound Hammer Test?
A non-destructive test known as the Rebound Hammer Test is used to evaluate the strength and uniformity of concrete. It entails using a spring-loaded hammer to strike the concrete’s surface and measuring how far it bounces back.
A tiny plunger on the rebound hammer makes contact with the concrete surface before being released to strike it. The hammer then bounces back off the surface, and a spring-loaded indicator on the hammer measures the distance of the rebound. The surface hardness of the concrete is then determined using the rebound distance.
This Test is useful for evaluating concrete quality in situ because it can quickly ascertain whether concrete strength is uniform across a surface. It is frequently employed in the construction sector to evaluate the durability of concrete constructions like roads, buildings, and bridges.
It should be noted that the Rebound Hammer Test does not replace more exact testing procedures; rather, it offers only an estimate of the compressive strength of concrete.
Who & When Invented the Rebound Hammer?
Engineer Ernst Schmidt from Switzerland invented the rebound hammer in the late 1940s. To provide a quick and non-destructive method for evaluating the strength of concrete structures, Schmidt created the device.
To produce and market the rebound hammer and other testing tools for building materials, he established the business Proceq SA in 1954. It is for use in the construction industry and is now produced by many manufacturers after the original Schmidt hammer design underwent numerous updates and modifications.
How to collect data from the Rebound Hammer?
The steps below are to collect data from a rebound hammer:
Check to make sure the surface being tested is dry, clean, and free of any debris or loose objects.
Place the plunger perpendicular to the surface being tested while securely holding the rebound hammer by the handle. Until the spring is completely compressed, press the plunger firmly against the surface.
After releasing the plunger, let it bounce back off the ground. The graduated scale of the hammer shows the plunger’s rebound distance.
Note the rebound value that was shown on the scale. Calculate the average rebound value by taking several readings at various points on the surface being tested.
Calculate the surface hardness of the material being tested using the rebound values. To ascertain the relationship between rebound values and material hardness, consult the calibration chart provided by the manufacturer.
For future reference, enter the rebound values and corresponding hardness estimates in a report or database.
It is significant to note that some variables, including the state of the surface being tested, the age and quality of the hammer, and the operator’s skill, can affect the accuracy of the rebound hammer. To ensure accurate and trustworthy results, it is advised to adhere to proper testing procedures and calibrate the hammer regularly.
When To Use the Rebound Hammer
In the building sector, the rebound hammer is a frequently used tool to assess the durability and caliber of concrete structures.
It is a non-destructive testing technique that makes it simple and quick to determine how hard the surface of concrete and other building materials is. It has a variety of uses, including.
Quality Control: It can be used to evaluate the strength of existing concrete structures or the caliber of newly cast concrete. The test can be used to find any weak points or areas of poor quality that might need improvement.
Upkeep and Repair: This is useful for checking on the condition of existing concrete structures and identifying any damage or deterioration that might have developed over time. The planning of maintenance and repair tasks as well as the prevention of expensive and disruptive failures can be done using this information.
Research and Development: To assess novel concrete mixtures or building techniques, the rebound hammer is frequently used in research and development. It can offer insightful information on the durability and strength of various tools and methods.
How to Use These Tools?
- Familiarize yourself with the components of a rebound hammer: a spring-loaded mass and a plunger.
- Make sure the concrete surface is clean and free of loose particles or debris.
- Hold the rebound hammer perpendicular to the surface being tested.
- Press the plunger firmly into the concrete surface and release it.
- Note the rebound distance of the hammer’s mass from the surface.
- Repeat the process at several locations to ensure representative results.
- Record the rebound values obtained from each test point.
- Compare the readings with the reference table to determine concrete strength.
- Interpret low rebound values as potential areas of weak concrete.
- Use rebound hammer results to assess concrete quality and plan for necessary repairs or reinforcement.
In general, the rebound hammer is a useful instrument for assessing the durability and caliber of concrete and other building materials. In terms of quality control, maintenance, and research applications, it is a non-destructive testing technique that can deliver prompt and accurate results.
