Rebound hammer testing in concrete is a non-destructive method that estimates surface hardness and, indirectly, compressive strength by measuring the rebound energy of a spring-loaded mass impacting the concrete surface.
A rebound hammer graph with a custom or manufacturer's conversion curve converts the Q or R rebound index to a compressive strength value in MPa, or hammers with data logging can do so automatically.
Conversion Curves for the Original Schmidt and Silver Schmidt Hammers are available below for users who need to make a manual conversion or learn how to read a rebound hammer graph.
The most common concrete rebound hammer form factor has a mechanism similar to a nail punch; the impact energy that is "bounced" back from striking the material's surface is converted to a dimensionless Index related to surface hardness.
How do I read a Rebound Hammer Graph / Convert to Strength?
Ideally, a user will create a custom curve by breaking compressive-strength test samples with their Schmidt Hammer and establishing a specific relationship for the concrete mix.
The user then either uses the graph of MPa vs Q/R Rebound Coefficient to convert the raw output, or uses the formula for that relationship and their hammers' Custom Material function to add an automatic conversion.
Conversion Graphs for Original Schmidt and OS8000 Original Schmidt Live.
The image below shows the most common manufacturer curve used in Australia, converting the rebound value R from a data set of Cylinder Sample breaks at 15-56 days of age. These samples were simple mixes of Portland or blast furnace slag cement with sand and gravel.
The user will find the rebound value on the horizontal axis, then find the corresponding point on the red conversion curve marked with the matching Original Schmidt alignment. They may then read the conversion from the vertical column.
The Original Schmidt Manual includes additional conversion curves. You may download it here.
Conversion Graphs for Silver Schmidt Live OS8200 and Silver Schmidt PC/ST
The image below combines the Traditional N and the lower 10th percentile reference curves used with PC/ST Silver Schmidt models, along with the current Silver Schmidt Live OS8200 model.
The lower 10th percentile curve is derived from research combining 2,300 data points. It provides a conservative safety margin by plotting the line of best fit on the conversion graph, ensuring that 90% of the data points lie above it.
The reference N curve is a European curve created on 28-day concrete to bridge 10-100 Mpa concrete mixes.
Both curves in the conversion graph were created using cube samples, so a Cylinder Factor should be used for Australia or NZ with data logging functions or manual adjustments based upon Table 7 in EN206.
The form factor for the standard cylinder ranges from 0.8 to 0.87.
How do I create a custom curve?
A custom correlation curve will provide a better relationship with the concrete mix it is created for and a more reliable, accurate MPa conversion.
To create the curve, a lab will need to prepare test specimens, test the samples at pre-determined intervals as the concrete cures, chart the results on a graph and establish a line of best fit and the formula for this relationship.
The formula may then be entered into the Schmidt Hammer's data logging functions or used in the graph for manual conversion.
The full process is explained in this Proceq reference document.
What Schmidt Hammer Should I Choose?
In general, a Type N hammer is the correct choice for general-purpose testing; Type L rebound hammers are specifically used for weak, thin, or unsupported concrete elements.
A Silver Schmidt has a slightly extended range of concrete strength, which may be measured.
The following chart shows the relative strength range of each hammer in the Screening Eagle Technology / Proceq range.
There are also specialist versions for Rock Strength, Super Low-strength concrete or mortar and Paper Roll testing.
Why PCTE Should Be Your First Choice for Concrete Rebound Hammer Tester
At PCTE, we provide the industry’s most reliable and precise concrete rebound hammer testers. Our concrete hammer test machines provide precise, repeatable measurements that assess concrete surface hardness and correlate it with compressive strength.
Built for both field and laboratory use, PCTE's rebound hammer equipment is designed to withstand tough conditions while delivering dependable results.
The testers are user-friendly, lightweight, and portable, allowing you to quickly measure surface hardness and assess concrete strength on-site with minimal preparation.
From construction projects to quality control, our concrete hardness tester rebound hammers are ideal for assessing the strength and condition of concrete surfaces in various industries. PCTE offers expert advice, calibration services, and full technical support, ensuring that you get the most accurate readings from your Schmidt hammer or other rebound hammer equipment.
Concrete Rebound Hammer Testing: Why Choose It for Your Projects?
Concrete rebound hammer testers use the rebound principle to measure the hardness of concrete surfaces, which can then be correlated with compressive strength. The Schmidt hammer, one of the most widely used rebound hammer equipment, works by striking the surface with a spring-loaded hammer and measuring the rebound. This provides a quick, non-destructive way to estimate concrete strength in the field or the laboratory.
Using a rebound hammer tester is ideal for quality control during construction, monitoring the condition of existing concrete structures, or assessing the effectiveness of concrete curing. Concrete rebound hammer testers are essential for ensuring that concrete surfaces meet the required strength and durability standards for safety and long-term performance.
Explore More
PCTE provides an extensive selection of concrete rebound hammer testers, ensuring you find the right tool for your concrete testing needs:
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Software Solutions: Our advanced software solutions make it easier to manage and analyse the data collected from your concrete hammer test machine, helping you generate reports and track test results.
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Non-Destructive Testing: Our NDT equipment includes rebound hammers and other tools that enable accurate testing of concrete without damaging the material.
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CMT Laboratory Equipment: In addition to rebound hammer testers, PCTE offers CMT laboratory equipment for more in-depth concrete testing and analysis.
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GPR Equipment: Ground Penetrating Radar (GPR) is essential for inspecting concrete structures and detecting embedded elements, complementing the rebound hammer equipment for comprehensive material assessment.
Warranty & Returns
PCTE offers a warranty on all concrete rebound hammer testers and related equipment. If your Schmidt hammer or concrete hammer test machine malfunctions or is damaged during the warranty period, please contact us for assistance. Returns are accepted within 7 days for unused equipment in its original condition. For more details, refer to our Warranty & Returns Policy or contact us via our Contact Us page.
Shipping & Delivery
PCTE ensures fast and reliable delivery for all concrete rebound hammer testers. Estimated delivery times will be provided during checkout. For more information, please refer to our Shipping & Delivery Policy or contact us via the Contact Us page for specific shipping inquiries.
FAQs
What is the principle behind Schmidt hammer testing?
The Schmidt hammer works on the rebound principle. It uses a spring-loaded mass that strikes the concrete surface. The rebound of the mass is measured, which indicates the concrete’s surface hardness. This rebound value can then be used to estimate the concrete's compressive strength, making it an effective tool for non-destructive testing of concrete surfaces.
How accurate is the concrete rebound hammer tester?
Concrete rebound hammer testers provide reliable, accurate results for surface hardness, typically with a correlation between rebound values and compressive strength. However, accuracy depends on factors such as surface smoothness, moisture content, and concrete uniformity. Proper calibration and understanding of the tool’s limitations are key to achieving consistent results.
What is the best way to use a rebound hammer tester?
To use a rebound hammer tester effectively, hold the device perpendicular to the concrete surface and strike the test surface with a firm, consistent motion. Ensure that the concrete surface is clean and smooth for optimal measurements. Repeat tests at different locations on the surface to ensure a consistent reading and improve the reliability of your results.
Can rebound hammer equipment be used on all types of concrete?
Rebound hammer equipment is suitable for most types of concrete, but its accuracy may be affected by factors such as the concrete’s age, moisture content, or surface condition. For best results, test on smooth, clean surfaces free of surface defects. Schmidt hammer testing may not be as effective on very rough or textured surfaces.
What are the key applications of concrete rebound hammer testers?
Concrete rebound hammer testers are commonly used in:
Construction: For on-site testing of new concrete surfaces to ensure proper strength and durability.
Quality Control: To monitor the consistency of concrete strength during construction projects.
Maintenance & Inspection: For evaluating the condition of existing concrete structures like bridges, roads, and buildings.
Research: To assess and test concrete properties in laboratory settings for academic or commercial research.
Does a concrete rebound hammer tester require surface preparation?
Yes, surface preparation is important for accurate results. The concrete surface should be smooth, clean, and free from contaminants such as dirt, dust, or coatings. For rough surfaces or when the surface condition is in doubt, it is recommended to prepare a small test area to ensure consistent readings.
Can rebound hammer equipment detect cracks or defects in concrete?
While rebound hammer equipment is excellent for assessing surface hardness and compressive strength, it is not designed to detect cracks or defects within the concrete. For more detailed inspection of concrete structures, complementary tools such as GPR equipment or ultrasonic testing may be necessary to detect subsurface issues.
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