TEST OF STONES
In a civil Engineering have some test on stones
- Acid Test
- Absorption Test
- smith's Test
- Resistance or crushing
- Hardness
- Toughness
Acid Test
This test shows the power of stone to withstand atmospheric actions, gases and acid fumes, 100 gms of stone chips fo stone chips are kept immersed in a 5 percent solution of dilute sulphuric acid or hydrochloric acid for three days. After taking out chippings, if the edges and corners remain sharp as they were before, it indicates that the stone is sound to resist weathering action.
Water .
Then
Absorption of water = (w2-w1)×100/w1
This is expressed in percentage.
Resistance to crushing
The crushing strength of stone may be tested in a crushing testing machine. Testing blocks are usually 10 cm cubes.
Three Nos of blocks to be testing. These specimen blocks are placed in water for 72 hours, after 72 hours the specimens are taken out from water. The surface of specimen is covered with plaster of paris the load is then applied axially on the cube in a crushing testing machines. The rate of loading 13.72 N/mm2 per minute. The crushing strength of the stone per unit area is the maximum load at which it's sample crushes or fails divided by the bearing face of the specimen.
Absorption test
Keep 50 GM's of stone chippings in an over at 105°C for three days and then cool in a desiccator. Now immerse the sample in distilled water for three days and takes the weight w2 of the wet sample on taking out from distilled.Water .
Then
Absorption of water = (w2-w1)×100/w1
This is expressed in percentage.
Smith's test
A piece of stone chip having small size and which one is freshly quarried is kept in a glass of clean water, one third full. Stir the water for half an hour. If only slightly cloudness is present, that mean stone is good and durable. If the water is too dirty. It will indicate that the stone contains too much of soluble earthy and mineral matters.Resistance to crushing
The crushing strength of stone may be tested in a crushing testing machine. Testing blocks are usually 10 cm cubes.
Three Nos of blocks to be testing. These specimen blocks are placed in water for 72 hours, after 72 hours the specimens are taken out from water. The surface of specimen is covered with plaster of paris the load is then applied axially on the cube in a crushing testing machines. The rate of loading 13.72 N/mm2 per minute. The crushing strength of the stone per unit area is the maximum load at which it's sample crushes or fails divided by the bearing face of the specimen.
Hardness
Hardness of a stone is tested by scratching the stone with a knife.- A cylinder of diameter 25 mm and hight 25 mm is taken out from the sample of stone.
- It is weighed
- The sample is placed in Dorry's testing machines and it is subjected to a pressure of 1250 gm.
- Annular steel disc machine is then rotated at a speed of 28 rpm.
- During the rotation of the disc, coarse sand of standard specification is sprinkled on the top of disc.
- After 1000 revolution, specimen is taken out and weighed.
- The coefficient of hardness is found out from the following equation.
- Coefficient of hardness=
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