Civil Engineering - Building Materials - Discussion

Hardness Test:

For determining the hardness of a stone, the test is carried out as follows:

i. A cylinder of diameter 25mm and height 25mm is taken out from the sample of stone.
ii. It is weighed.
iii. The sample is placed in Dorry\'s testing machine and it is subjected to a pressure of 1250 gm.
iv. Annular steel disc machine is then rotated at a speed of 28 rpm.
v. During the rotation of the disc, coarse sand of standard specification is sprinkled on the top of the disc.
vi. After 1000 revolutions, the specimen is taken out and weighed.
vii. The coefficient of hardness is found out from the following equation:

Coefficient of hardness = 20 - loss of wt. in gm/3.

Dorry testing machine is used for abrasion test but it is not given in option so it's a hardness test.

Resistance against abrasion is called Hardness. So, it's a hardness test.

No @Devendra.

The Correct answer is hardness test.

Mohr's scale is used to determine for stones.

Dorry abrasion test I think hence hardness.

Why is '20' in the formula taken for?

Absorption test is right.