Tests on stones , Field test and laboratory test

 Tests on stones

Field Tests

1. Smith’s test: It is to check whether the stone contains muddy substance. A sample of stone is kept in a glass of distilled water for 24 hours and stirred well to remove muddy substance.

2. Toughness test: Stone is hit with a hammer and metallic sound is indication of strong stone.

3. Hardness test: Mohr’s hardness may be found by scratching the stone with knife.

Laboratory Tests

1. Crushing strength test: 40 × 40 × 40 mm cubes are used for testing. Load is applied in a compression testing machine at the rate 14 N/mm2 per minute. A stone with crushing strength more than 100 N/mm2 is treated as good stone.

2. Water absorption test: For good stone water absorption after 24 hours immersion in water, should not exceed 0.60.

3. Attrition test: Los Angeles abrasion test is conducted to find the resistance of the stone to surface wear. Los Angeles value recommended are (a) for bitumen mix: 30%, (b) for base course 50%.

4. Impact test: Impact testing machine consists of a frame with guides. A metal hammer weighing

13.5–15 kg falls from a height of 380 mm. Recommended values for various works are

• For wearing coat 30%

• For bituminous mechadam 35%

• For water bound mechadam 40%

5. Acid test: Sandstones are checked for the presence of calcium carbonate. Sample of 50–100 gm of stone is kept in 1% hydrochloric acid for seven days. If calcium chloride is present, edges are broken and powder is formed.

Common building stones Basalt, granite, sandstones, limestones, marble, quartzite, laterite and slate. Solid and hollow concrete blocks are known as artificial stones.