1. CE8391 CONSTRUCTION MATERIALS
UNIT I STONES – BRICKS – CONCRETE BLOCKS
Presentation By
Mr.P.Selvakumar.,B.E.,M.E.
Assistant Professor,
Department Of Civil Engineering,
Knowledge Institute Of Technology, Salem.
Tests on Stones
2. Tests on stones
1. Hardness test
2. Crushing test
3. Impact test
4. Fire resistance test
5. Attrition test
6. Acid test
7. Electrical resistance/water
absorption
8. Smith's test
9. Crystallization test
10. Microscopic Test
11. Freezing and thawing test
3. Hardness test
1. Hardness of a stone is tested by a pen knife.
2. Hardness is determined with the aid of Moh's scale of hardness.
3. If a pocket knife makes mark on a fresh surface of a stone say on
limestone, the hardness of that limestone may be taken as H = 3,
4. a scratch with the aid of a finger nail indicates a hardness of
H = 2.
5. Hard silicious rock which cannot be scratched by a knife
represents a hardness of H = 7.
6. Hardness test
• A cylinder of diameter 25 mm and height 25 mm is taken out from the
sample of stone.
• It is placed in Dorry's testing machine and pressed with a load of
1250 gm. It is then weighed.
• The annular steel disc of the machine is then rotated at a speed of
28 r.p.m.
• During rotation, coarse sand of standard specification is sprinkled on
top of the disc.
• After 1000 revolutions, the specimen is taken out and weighed.
7. Hardness test
Coefficient of hardness is found out from the following equation:
Coefficient of hardness = 20 -
Loss in weight in gm
3
8. Crushing test
• The sample of a stone is first cut in cubes of size 40 mm x 40 mm x 40 mm.
• The sides of the cube are then finely dressed and finished.
• The minimum number of specimens that can be tested is three.
• The specimens are placed in water for 72 hours prior to the test and there
after tested in saturated condition.
10. Crushing test
• The load-bearing surface is covered with a layer of plaster of Paris or a
5 mm thick plywood. Load is then applied axially on the cube with a
compreesive test machine. The rate of loading is 13.7 N/mm² per minute.
• The crushing strength of the stone per unit area is the maximum load at
which its sample For ordinary building works it is not necessary to carry
out crushing/strength test for stones.
• For example, the compression test on the stone in buildings does not
exceed 1 N/mm2, whereas even the weakest stone possesses much higher
compressive strength as illustrated in Table 2.1.crushes or fails divided by
the area of the bearing face of the specimen.
12. Impact test
• Impact test is carried out on an impact testing machine, to
determine the toughness of a stone.
• A cylinder of diameter 25 mm and height 25 mm is taken out from
the sample of stone.
• The sample is then placed on the cast-iron anvil of the machine.
14. Impact test
• A steel hammer of 20 N is allowed to fall axially in a vertical
direction over the specimen.
• The height of the first blow is 1 cm; that of the second blow 2 cm;
that of third blow is 3 cm; and so on.
• The blow at which the specimen breaks is noted. If it is the nth
blow n represents the toughness index of the stone.
15. Fire resistance test
The stone which is free from calcium carbonate can resist fire. The
presence of calcium carbonate in the stone can be detected by
dropping a few drops of dilute sulphuric acid which will produce
bubbles.
16. Attrition test
• The attrition test is carried out to determine the rate of wear of
stones employed for the construction of road.
• This test also known as abrasion test, is carried out in Deval's
attrition testing machine.
18. Attrition test
• The sample of stone is broken into pieces of about 60 mm size.
• Such pieces, weighing 50 N, are then put in both the cylinders of
Deval's attrition testing machine. The diameter and length of
cylinders are 200 mm and 340 mm respectively.
• The cylinders are then closed, their axes making an angle of 30°
with the horizontal.
• The cylinders are rotated about the horizontal axis for 5 hours at
the rate of 30 r.p.m.
19. Attrition test
• The contents are then taken out from the cylinders and passed through a
size of 1.5 mm mesh.
• The quantity of material which is retained on the sieve is then weighed.
The percentage wear is worked out at as follows:
• Percentage wear =
Loss in weight
Initial weight
x 100
20. Acid test
• In this test, a stone is kept for one week in the solution of sulphuric
acid and hydrochloric acid having 1% strength.
• The corners of stones which have high alkaline content turn
roundish and loose particles will get deposited on its surface.
• Such types of stones are unsuitable for smoky atmosphere.
• The stones having high percentage of lime content exhibit
efflorescence when subjected to action of acids.
21. Electrical resistance
• As the electrical resistance of a wet stone is less, therefore the stone
should be non-absorbent.
• Sandstones should not absorb more than 10% of water, 17% in case
of limestones and 1% in granites of their volume of water when
dipped for 3-4 hours.
22. Water absorption
• A cube weighing about 0.5 N from a given sample of the stone is
prepared. Its actual weight is recorded let it be W1 N
• The cube is then immersed in distilled water for 24 hours.
• It is then taken out of water and its surface wiped with a damp piece
of cloth. The cube is then weighed again; Let its weight be W2 N.
23. Water absorption
• The cube is suspended freely in water and its weight is recorded;
let it be W3, N.
• The cube is then kept in boiling water for five hours.
• It is then removed and its surface water is again wiped off with a
damp piece of cloth.
• It is then weighed, let its weight be W4 N.
24. Water absorption
From the above data, values of the following properties of the stone
are obtained:
Percentage of weight absorption after 24 hours =
W2−W1
W1
x 100
Percentage of porosity by volume =
(W4−W1)
(W2−W3)
x 100
Saturation coefficient =
Water absorption
Total Porosity
=
W2−W1
W4−W1
25. Smith’s test
1. This test indicates the presence of earthly matter.
2. The sample of the stone is broken into small pieces and put into a
test tube containing clear water.
3. The test tube is then shaken vigorously, the dirty colour will
show presence of argillaceous matter.
26. Crystallization test
1. This test determines the durability or weathering quality of a
stone.
2. A sample of stone is immersed in the solution of sodium sulphate
at room temperature and dried in hot air.
3. The process of wetting and drying is carried out for two hours;
the difference in weight if any is recorded.
4. Little difference in weight indicates durability and good
weathering quality of the stone.
27. Microscopic test
This is essentially a geologist's test. In this test, the sample of stone is
subjected to microscopic examination to study the following properties:
(1) Mineral constituents
(2) Average grain size
(3) Existence of fissures, pores, veins and shakes
(4) Texture of stone
(5) Nature of cementing material
(6) Presence of any harmful substance etc.
28. Freezing and thawing test
1. This test is carried out as follows:
2. The specimen of stone is kept immersed in water for 24 hours.
3. It is then placed in a freezing mixture at -12°C for 24 hours.
4. It is then thawed or warmed to atmospheric temperature. This
should be done in shade to prevent any effect due to wind, sun
rays, rain, etc.
5. The above procedure is repeated several times and behaviour of
the stone carefully studied.
