To determine the compressive strength of rocks using Schmitt hammer.

To determine the compressive strength of rocks using Schmitt hammer.

EQUIPMENTS REQUIRED: Rock samples, Cleaning cloth, Schmidt hammer

THEORY:

Schmidt hammer:

The Schmidt hammer which is also known as Swiss hammer, Rebound hammer. It is device, which used to measure surface hardness, penetration resistance and strength of rocks .It is a N.D.T (non-destructive test) instrument, which gives rebound number. Its rebound number depend upon the hardness of rocks. Rebound number can be used to determine the compressive strength of rocks by conversion graph. This instrument can be used in both laboratory and in site. It is very easy to use and portable and quite cheap.

Rebound number: The extent of rebound (a factor of surface hardness) is measured on graduated scale with is on Schmidt hammer. That measured extent of rebound on scale is termed as rebound number.

Compressive strength: It the capacity of material to resist the compression load (forces) which tends to reduce size and increase diameter.

Hardness:It is resistance of any material to abrasion forces.

PROCEDURE:

1. Select the area of 1 ft² .
2. Divide the area into three layers.
3. Clear the surface (from plants, funges etc) which is to be tested. If there is moisture or
4. water on surface which must be cleaned.
5. Perform the Schmidt hammer. It is done by following methods

• Unlock the hammer by pressing perpendicular to surface.
• Then gradually pushes the instrument towards the test surface until the hammer impacts.
• After the impact maintain the pressure on the instrument and press the side button on the instrument.
• Then rebound number is recorded to the nearest whole number.
• In order to ensure the accuracy 10 reading should be taken from each test area.

6. Average the reading of rebound number and determine the compressive strength through graph.

TEST SAMPLES

Average Rebound number:_________________________

GRAPH

RESULTS:

COMMENTS