Hardness Test for Building Stone

Hardness Test:
Hardness test is conduct to determine the resistance of stone to abrasive force cause by much wear and friction.

The test is carried out as follows:

1. A cylinder of diameter 25mm and height 25mm is taken out from the sample of stone.
2. It is weighed.
3. The sample is placed in Dorry’s testing machine and it is subjected to a pressure of 1250 gm.
4. Annular steel disc machine is then rotated at a speed of 28 rpm.
5. During the rotation of the disc, coarse sand of standard specification is sprinkled on the top of disc.

 After 1000 revolutions, specimen is taken out and weighed.

 The coefficient of hardness is found out from the following equation:
Coefficient of hardness = 20 - (Loss of Weight in gm)/3