Properties of Stones
Requirements of Good Building
Tests on Stones
Uses of stones
Stones, bricks, cement, lime and timber are the traditional materials used for civil engineering constructions for several centuries. In this chapter types, properties, tests and uses of these materials is explained.
Stone is a ‘naturally available building material’ which has been used from the early
age of civilization. It is available in the form of rocks, which is cut to
required size and shape and used as building block. It has been used to
construct small residential buildings to large palaces and temples all over the
world. Red Fort, Taj Mahal, Vidhan Sabha at Bangalore and several palaces of
medieval age all over India are the famous stone buildings.
Type of Stones
Stones used for civil engineering works may be
classified in the following three ways:
Based on their origin of formation stones are
classified into three main groups—Igneous, sedimentary and metamorphic rocks.
(i) Igneous Rocks: These rocks are formed by cooling and solidifying of the rock
masses from their molten magmatic condition of the material of the
earth. Generally igneous rocks are strong and durable.
Granite, trap and basalt are the
rocks belonging to this category, Granites are formed by slow cooling of the
lava under thick cover on the top. Hence they have crystalline surface. The
cooling of lava at the top surface of earth results into non-crystalline and
glassy texture. Trap and basalt belong to this category
Sedimentary Rocks: Due to weathering action of water,
wind and frost existing rocks disintegrates. The disintegrated material
is carried by wind and water; the water being most powerful medium. Flowing
water deposits its suspended materials at some points of obstacles to its flow.
These deposited layers of materials get consolidated under pressure and by
also contribute to the cementing of the deposits. The rocks thus formed are
more uniform, fine grained and compact in their nature. They represent a bedded
or stratified structure in general. Sand stones, lime stones, mud stones etc.
belong to this class ofrock.
(iii) Metamorphic Rocks: Previously formed igneous and sedimentary rocks under go changes
due to metamorphic action of pressure and internal heat. For example due to
metamorphic action granite becomes greisses, trap and basalt change to schist
and laterite, lime stone changes to marble, sand stone becomes quartzite and
mud stone becomes slate.
Based on the structure, the rocks may be classified as:
(i) Stratified Rocks:
These rocks are having layered structure. They possess planes of stratification
or cleavage. They can be easily split along these planes. Sand stones, lime
stones, slate etc. are the examples of this class of stones.
Unstratified Rocks: These rocks are not stratified.
They possess crystalline and compact grains. They cannot be split in to
thin slab. Granite, trap, marble etc. are the examples of this type of rocks.
Foliated Rocks: These rocks have a tendency to split
along a definite direction only. The direction need not be parallel to each
other as in case of stratified rocks. This type of structure is very common in
case of metamorphic rocks.
On the basis of their chemical composition engineers prefer to
classify rocks as:
Argillaceous rocks and
(i) Silicious rocks: The main
content of these rocks is silica. They are hard and durable. Examples of
such rocks are granite, trap, sand stones etc.
(ii) Argillaceous rocks:
The main constituent of these rocks is argil i.e.,
clay. These stones are hard and durable but they are brittle. They
cannot withstand shock. Slates and laterites are examples of this type of
The following properties of the stones should be
looked into before selecting them for engineering works:
(i) Structure: The
structure of the stone may be stratified (layered) or unstratified. Structured
stones should be easily dressed and suitable for super structure. Unstratified
stones are hard and difficult to dress. They are preferred for the foundation
(ii) Texture: Fine grained stones with homogeneous distribution look
attractive and hence they are used for carving. Such stones are usually
strong and durable.
(iii) Density: Denser stones are stronger. Light weight stones are weak. Hence
stones with specific gravity less than 2.4 are considered unsuitable for
(iv) Appearance: A stone with uniform and attractive colour is durable, if grains
are compact. Marble and granite get very good appearance, when polished.
Hence they are used for face works in buildings.
(v) Strength: Strength is an important property to be looked into before selecting
stone as building block. Indian standard code recommends, a minimum
of 3.5 N/mm2 for any building block.
Table 22.214.171.124shows the crushing strength of various stones. Due to
non-uniformity of the material, usually a factor of safety of 10 is used to
find the permissible stress in a stone.
Hence even laterite can
be used safely for a single
storey building, because in such
structures expected load can hardly give a
stress of 0.15 N/mm2. However in stone masonry buildings care should
be taken to check the stresses when the beams (Concentrated Loads) are placed
on laterite wall.
Crushing strength of common building stones
Name of Stone :
Crushing Strength in
Trap 300 to 350
Basalt 153 to 189
104 to 140
Marble 70 to 210
(vi) Hardness: It is an important property to be considered when stone is used
for flooring and pavement. Coefficient of hardness is to be found by
conducting test on standard specimen in Dory’s testing machine. For road works coefficient of hardness should
be at least 17. For building works stones with coefficient of hardness less
than 14 should not be used.
(vii) Percentage wear: It is measured by attrition test. It is an important property
to be considered in selecting aggregate for road works and railway
ballast. A good stone should not show wear of more than 2%.
(viii) Porosity and
Absorption: All stones have pores and hence
absorb water. The reaction of water with material of stone cause disintegration.
Absorption test is specified as percentage of
water absorbed by the stone when it is immersed under water for 24 hours. For a
good stone it should be as small as possible and in no case more than 5.
(ix) Weathering: Rain and wind cause loss of good appearance of stones. Hence
stones with good weather resistance should be used for face works.
(x) Toughness: The resistance to impact is called toughness. It is determined
by impact test. Stones with toughness index more than 19 are preferred
for road works. Toughness index 13 to 19 are considered as medium tough and
stones with toughness index less than 13 are poor stones.
(xi) Resistance to Fire: Sand stones resist fire better. Argillaceous materials, though
poor in strength, are good in resisting fire.
(xii) Ease in Dressing: Cost of dressing contributes to cost of stone masonry to a
great extent. Dressing is easy in stones with lesser strength. Hence an
engineer should look into sufficient strength rather than high strength while
selecting stones for building works.
(xiii) Seasoning: The stones obtained from quarry contain moisture in the pores.
The strength of the stone improves if this moisture is removed before
using the stone. The process of removing moisture from pores is called
Requirements of Good
The following are the requirements of good building stones:
(i) Strength: The stone should be
able to resist the load coming on it.
Ordinarilly this is not of primary concern since
all stones are having good strength. However in case of large structure, it may
be necessary to check the strength.
(ii) Durability: Stones selected should be capable of resisting adverse effects
of natural forces like wind, rain and heat.
Hardness: The stone used in floors and pavements should
be able to resist abrasive forces caused by movement of men and
materials over them.
Toughness: Building stones should be tough enough to sustain
stresses developed due to vibrations. The vibrations may be due to the
machinery mounted over them or due to the loads moving over them. The stone
aggregates used in the road constructions should be tough.
Specific Gravity: Heavier variety of stones should be
used for the construction of dams, retaining walls, docks and harbours. The
specific gravity of good building stone is between 2.4 and 2.8.
(vi) Porosity and Absorption:
Building stone should not be porous. If it is porous rain water enters into the
pour and reacts with stone and crumbles it. In higher altitudes, the freezing
of water in pores takes place and it results into the disintegration of the
(vii) Dressing: Giving required shape to the stone is called dressing. It
should be easy to dress so that the cost of dressing is reduced. However
the care should be taken so that, this is not be at the cost of the required
strength and the durability.
(viii) Appearance: In case of the stones to be used for face works, where
appearance is a primary requirement, its colour and ability to receive
polish is an important factor.
(ix) Seasoning: Good stones should
be free from the quarry sap.
should not be used for 6 to 12 months after quarrying. They are allowed to get
rid of quarry sap by the action of nature. This process of removing quarry sap
is called seasoning.
(x) Cost: Cost is an important consideration in selecting a building
material. Proximity of the quarry to building site brings down the cost
of transportation and hence the cost of stones comes down.
However it may be noted that not a
single stone can satisfy all the requirements of a good building stones, since
one requirement may contradict another. For example, strength and durability
requirement contradicts ease of dressing requirement. Hence it is necessary
that site engineer looks into the properties required for the intended work and
selects the stone.
To certain the required
properties of stones, the following tests can conducted:
(i) Crushing strength
(ii) Water absorption
(iii) abrasion test
(iv) Impact test
(v) Acid test.
Stones are used in the
following civil engineering constructions:
(i) Stone masonry is
used for the construction of foundations, walls, columns and arches.
(ii) Stones are used
(iii) Stone slabs are
used as damp proof courses, lintels and even as roofing materials.
(iv) Stones with good
appearance are used for the face works of buildings. Polished marbles and
granite are commonly used for face works.
(v) Stones are used for
paving of roads, footpaths and open spaces round the buildings.
(vi) Stones are also
used in the constructions of piers and abutments of bridges, dams and retaining
(vii) Crushed stones
with graved are used to provide base course for roads. When mixed with tar they
form finishing coat.
(viii) Crushed stones
are used in the following works
also: (a) As a basic inert material in
(b) For making artificial stones and building blocks
(c) As railway ballast.