Concrete Test Hammer

Concrete Test Hammer

Concrete test hammer uses indirect means of obtaining relative value for compressive strength of finished concrete. Spring-driven hammer is used for non-destructive quality testing of concrete and other building materials in any structure or prefabricated section. Determines when forms may be removed or load applied, damage done to a structure by freezing or fire. Impact energy is 1.6 ft-lbs. (2.207 Nm). Unit has 1450 to 10,150 psi (10 to 70 N/mm2) capacity range. Lightweight portable test instrument works on the rebound principle. To operate, place impact plunger against test surface and apply pressure until plunger disappears; hammer will release. Scale pointer reading gives rebound value in percent of the forward movement of the hammer mass. Includes rubbing stone, plastic case, instruction booklet and calibration curves. Meets ASTM C805

A Schmidt hammer, also known as a Swiss hammer, is a device to measure the elastic properties or strength of concrete or rock.

Original Schmidt Concrete Test Hammer
The hammer measures the rebound of a spring loaded mass impacting against the surface of the sample. When conducting the test the hammer should be held at right angles to the surface which in turn should be flat and smooth. The rebound reading will be affected by the orientation of the hammer, when used in a vertical position (on the underside of a suspended slab for example) gravity will increase the rebound distance of the mass and vice versa for a test conducted on a floor slab. The Schmidt hammer is an arbitrary scale ranging from 10 to 100. Schmidt hammers are available from their original manufacturers in several different energy ranges. These include: (i) Type L-0.735 Nm impact energy, (ii) Type N-2.207 Nm impact energy; and (iii) Type M-29.43 Nm impact energy.
The test is also sensitive to other factors:
Local variation in the sample. To minimise this it is recommended to take a selection of readings and take an average value.
Water content of the sample, a saturated material will give different results from a dry one.
Prior to testing, the Schmidt hammer should be calibrated using a calibration test anvil supplied by the manufacturer for that purpose. 12 readings should be taken, dropping the highest and the lowest, and then take the average of the ten remaining. Using this method of testing is classed as indirect as it does not give a direct measurement of the strength of the material. It simply gives an indication based on surface properties, it is only suitable for making comparisons between samples.