Concrete Test Hammer, Type N
This Concrete Test Hammer is for fast, inexpensive, nondestructive testing of in-place concrete strength. Plastic case and rubbing stone included.
Hammer tests will help you decide where to take concrete test cores and where damage is from freezing or fire. Useful range is for concrete strengths from 1,400—8,000 psi (10—55mPa). Rebound of the mass is recorded on the concrete test hammer as the “rebound number”. The hammer mass in a rebound hammer test is critical to the impact energy applied to the concrete.
Included calibration curves provide estimated concrete strength from rebound number, but accuracy of concrete test hammers is greatly improved by user-produced laboratory correlations with compression tests on the same type of concrete being tested.
What are Concrete Test Hammers
Concrete test hammers, also known as rebound hammers or Schmidt hammers, are handy tools to assess the quality of hardened concrete. These hammers measure the surface hardness of concrete, which can relate to concrete strength when compared to laboratory test results. The test hammer is a cheap way to decide if you need to do more testing and it can give more value than just estimating in-place compressive strength. By using a test hammer, professionals can quickly identify where to investigate further, saving time and resources in the process. These tools are key to ensuring concrete structures are sound and durable.
Concrete Test Hammer Test Methods
This concrete test hammer meets the following test methods:
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ASTM C 805
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BS 1881-202
Other factors that can affect the rebound hammers are the angle of the hammer during the test, surface moisture and mix design, which is why you need to consider multiple variables when interpreting the test results.
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How to use the Test Hammer
To use a test hammer, you need to first select and prepare the test area. Factors that directly affect the rebound hammers and numbers are moisture, surface texture, age, carbonation depth, proximity of aggregate, steel reinforcement and air voids. The test surface should be saturated with water several hours before taking rebound readings. You then hold the hammer at 90 degrees to the test surface and strike the surface with the hammer’s spring-loaded mass. The rebound value is then recorded. This process will give you accurate readings that reflects the true condition of the concrete. Proper preparation and execution is key to getting reliable results.
Types and Calibration
There are two types of concrete test hammers that produce different impact energies. The Type L hammer has lower impact energy, for softer materials like mortar joints, low-strength concrete, plaster, masonry mortar and paper rolls. The Type N hammer has higher impact energy, for harder materials. Schmidt hammers are available from manufacturers in several different energy ranges, Type L-0.735 Nm impact energy, Type N-2.207 Nm impact energy, Type M-29.43 Nm impact energy.
Before testing, the Schmidt hammer should be calibrated using a calibration test anvil supplied by the manufacturer. The test is governed by ASTM C805, a European and international standards for testing concrete in concrete structures is EN 12504-2, and ASTM D5873 describes the procedure for testing of rock. The calibration curves should be checked regularly to get accurate results.
The test hammer comes with a durable padded nylon carrying case, a rubbing stone, an instruction manual and a calibration chart. The carrying case has a loop handle for easy carrying. The rubbing stone is used to clean the test surface before taking readings. The instruction manual has step by step instructions on how to use the test hammer and interpret the results. The calibration chart is used to convert the rebound hammers and the value to a specific compressive strength in psi or mPa.
So there you have it. Concrete test hammers are a must have tool for testing hardened concrete. Get to know how to use it, choose the right one and calibrate it.