Test for Stones
Some of the simple test for stones are listed below,
(a) Crushing test for stones: The crushing strength of a stone greatly depends upon its texture and specific gravity. A stone of even texture arid of specific gravity greater than 2.7 can take heavy loads. Safe compressive loads on stones should be taken not more than one-tenth of the crushing loads determined by cube test. Stones generally begin to crack or split under about half of their crushing loads.
(b) Porosity or absorption test : Porous stones such as coarse grained sandstones should not be used. A good building stone should not absorb more than 5 per cent of its weight of water after 24 hours immersion. Any stone absorbing more than 10 per cent or having specific gravity less than 25 should be rejected.
(c) Structure test : Small pieces of the stone are kept for about an hour in a glass of water and then shaken vigorously. 1f the water gets dirty it shows the stone particles are not properly cemented together.
(d) Acid test : A small sample is immersed into 1 per cent solution of hydrochloric acid and kept for about seven days. During this time the solution is frequently agitated. If the sample has still maintained its edges and corners as sharp as before, the stone will weather well. If a drop of weak sulphuric or hydrochloric acid on a piece of stone causes effervescence, the stone contains chalk and is poor in weathering qualities unless it is marble.
(e) Hardness test for stones: may be tested by scratching with a penknife, which should not make an impression on a hard stone.
(f) Toughness : may be tested by breaking the stone under a hammer. A hard and tough stone is required for road mental.
These are the simple tests.