Concrete rebound Schmidt hammer (sclerometer) – is a device for concrete and other building materials strength testing. The most common in the world instrument for measuring the strength of concrete is the Schmidt Hammer. The device is called by the name of the engineer Ernst Schmidt, who invented the construction of the sclerometer.
The method is based on the impacting the impact plunger on the concrete surface with predetermined (normed) impacting energy and subsequent measuring of the height of the striker rebounding. The height of the striker rebounding will be proportional to the strength of concrete. The strength of concrete is determined with the calibration charts that are supplied with the instrumen.
Concrete Rebound Schmidt Hammer is very ease in operation, has good reliability of design and high measurement accuracy, so that this method is the most common method of measuring the strength of concrete in the world. The strength testing with the Schmidt hammer is correspond with ASTM C 805; ASTM D 5873 (for rock); DIN 1048, p. 2; ENV 206; EN 12 504-2; ISO / DIS 8045.
There are several versions of the device, which are different in impacting energy.
> The most “powerful” Schmidt hammer is designed to measure the strength of concrete with a thickness of 70-100mm and more, also for the strength testing of massive rocks with impact energy – 2,207J (Nm). This is the base and the most common model of Schmidt hammer, about 90% of the Schmidt hammers in the world have the same impact energy.
>Average “powerful” Schmidt hammer has the 735J (735 Nm) impacting energy. The impact energy is reduced threefold in compared with the base model. The main application of this instrument is measuring the strength of bricks and concrete products with a wall thickness less than 100 mm and small sizes of sample, also it used for testing the less strength stones and rocks.
>The least “powerful” Schmidt hammer has 196J (196Nm) impact energy. The main purpose is the strength testing the mortar of brick masonry.