Rebound Hammer Test Procedure Pdf
Rebound hammer test graph describes the correlation between the strength of concrete and rebound number. The non-destructive tests are the group of useful methods to evaluate the strength of construction materials without causing damage.
Surface and internal moisture condition of the concrete. It is necessary to calibrate the rebound hammer before carrying out the test on hardened concrete. The operation of the hammer is very simple, yet it is not so simple as to entrust this tool to a raw hand for taking readings of a structure. By pushing a button, the rider can be held in position to allow readings to be taken. We have also discussed the use of rebound hammer test and its limitations.
Some times, in case of failure of cubes, doubtful concrete, cracks, deterioration of concrete, etc. As far back as early thirties, the necessity was felt to develop instruments by which in-situ strength of concrete may be obtained. The cube size must be increased with the increase of hammer impact energy. Trowelled and floated surfaces as in floors, are harder than moulded surfaces and in most cases will tend to overestimate the strength.
Software Database Civil Engineering Links. Its operation, calibration, taking readings of a concrete structure, analysis and interpretation of the test data must always be carried out by specialists trained for this purpose. Free or trowelled surface may also be satisfactory if appropriate corrections are applied or a special calibration is prepared. Calibration or corrections for a given direction of test are supplied with the hammer or can be derived. Because I am usually using Wm in calculated hammer test result.
These factors need to be considered in interpreting rebound numbers. Kaushal Kishore Vincent T. The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes.
For reliable results the calibration curve shall be drived from the given set of materials and conditions. Do not touch the button while depressing the plunger. They are independent tests sufficient to make the structural engineering decisions after establishing figurative substantiation through its application. Gravel and most crushed rocks give similar correlations, but lightweight aggregates and aggregates with unusual properties require special calibration. Always use rebound hammer perpendicular to the plane of a concrete component or any other materials.
PDF) REBOUND HAMMER TEST METHOD STATEMENT
Each hammer varies considerably in performance and needs calibration for use on concrete made with aggregates produced from a specific source. Apply a gradual increase in pressure until the hammer impacts. The underlying principle of the rebound hammer test is. Inspite of its popularity, this testing has not been standardized in any country till except in Bulgaria. When completely retracted the spring is automatically released.
In addition, the number of test cubes is generally so small that they can only be considered as random tests. Procedure to determine strength of hardened concrete by rebound hammer.
Many things can affect concrete surface hardness. The concrete test hammer is an excellent tool in the hands of experts.
The concrete strength will be valid only if they are all standardised for the concrete under test and for the calibration specimens. Material Exhibition Explore the world of materials. Press the button after impact, in case it is not convenient to note the rebound reading in that position.
Rebound Hammer Test
The accuracy of the hammer reproducibility should be ascertained from time to time using a standard anvil, particularly before the testing of structure. This will be of great help to all civil engineers seeking information on Rebound Hammer test. When the plunger is pressed against, the surface of concrete, it retracts against the force of the spring. It is necessary to recalibrate the hammer for different types of cement.
Non-destructive Testing Of Concrete By Rebound Hammer
The compressive strength is then determined by taking average of rebound reading. Avoid rough spots, hony-comb or porous areas. At least two replicate cores shall be taken from at least six locations with different rebound numbers. Calibration should, therefore, be carried out with great care and on a larger number of specimens.
Its popularity is due to its hardness of the concrete, it is important to relatively low cost and simple operating understand all the items that might affect surface procedures. Here are the procedure of rebound hammer test and precaution while performing the test.
It is interesting to note that to tests are needed to plot calibration curves for rebound hammer. Small air pockets near the surface under the point of impact cause low rebound, on the other hand, immediately over a hard aggregate the impact will result in a high rebound. But if the major difference found in results, then we need to calibrate the rebound hammer before testing. If it is found that hammer performance is doubtful, ensaio sobre a cegueira jos saramago pdf the hammer should be changed.
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