building materials1_architecture_Classification of rocks, Sources, Seasoning, Quarrying of stones, Dressing, Characteristics of stones, Testing of stones, Common building stones and their uses. Masonary and paving. Stone veneering, preservation of stones Deterioration of stones, Durability, Preservation, Selection of stones, Artificial stones.

1. STONES
General classification of materials
 Cement (binding) materials : lime, cement, mortar, etc
 Protective materials: paints, varnishes, plaster, etc and
 Solid materials: stones, bricks, iron, timber, etc.
Classification of rocks
 The building stones obtained from the rocks are classified in the following three ways;
o Geological classification
o Physical classification
o Chemical classification
Geological classification
 According to this classification, rocks are of 3 types:
o Igneous rocks
o Sedimentary rocks
o Metamorphic rocks
Igneous rocks
 The molten or pasty rocky material present inside the earth’s portion is known as ‘Magma’.
 This magma occasionally tries to come out on the earth’s surface through cracks or weak
portions.
 The rocks which are formed by the cooling of magma are known as the ‘Igneous rocks’.
 The igneous rocks are recognized in the following 3 classes:
o Plutonic rocks
o Hyabassal rocks
o Volcanic rocks.
Plutonic Rocks
 Rocks formed due to the cooling of magma at a considerable depth from earth’s surface are
‘Plutonic rocks’.
 The cooling is slow & the rocks posses coarsely grained crystalline structure.
1

2. STONES
 These rocks are commonly used in building industry.
 Granite is the leading example of this type of rock.
Hypabassal Rocks
 Rocks formed due to cooling of magma at a relatively shallow depth from the earth’s surface
are ‘Hypabassal rocks’.
 The cooling is quick & hence, the rocks posses finely grained crystalline structure.
 Dolerite is an example of this type of rock.
Volcanic Rocks
 Rocks formed by the pouring of magma at the earth’s surface are ‘Volcanic rocks’.
 The cooling is very rapid & these rocks posses extremely fine grain in structure.
 They sometimes contain some quantity of glass which is a non-crystalline material.
 Basalt is an example of this type of rock.
Sedimentary Rocks
 These rocks are formed by the deposition of products of weathering on pre-existing rocks.
 The products of weathering are carried away from their place of origin by agents of
transport, such as frost, rain, wind, flowing water, etc.
 Following four types of deposits occur;
o Residual deposit: Some portion of the products of weathering remains at site of
origin. These are ‘Residual deposit’.
o Sedimentary deposit: Insoluble products of weathering are carried away in
suspension is deposited & these form the sedimentary deposit.
o Chemical deposit: Products of weathering carried away in suspension are deposited
by physio-chemical processes such as evaporation; precipitation, etc give rise to
chemical deposits.
o Organic deposits: Products of weathering carried away & deposited by agency of
organisms are known as organic deposit.
 Examples of sedimentary rocks are gravel, sandstone, limestone, gypsum, lignite, etc.
Metamorphic Rocks
2

3. STONES
 These rocks are formed by the change in character of the pre-existing rocks.
 Igneous & sedimentary rocks, change character when subject to great heat & pressure.
 This process is known as ‘Metamorphism’.
 The mineral composition & texture of a rock are in equilibrium with its surrounding in a
system.
 Increase in heat & pressure, upsets this equilibrium & metamorphism occurs.
 In this process, the original mineral constituents become unstable due to heat & pressure &
get converted into new environment around.
 However, changes produced by weathering & sedimentation are ‘not’ included in
metamorphism.
 Three agents of metamorphism are heat, pressure & chemically acting fluids.
 Pressure can be uniform or directed.
o Uniform – solids & liquids
o Directed – only for solids
 Following 4 types of metamorphism occur with the combinations of heat, uniform pressure &
directed pressure.
o Thermal Metamorphism: Heat is the pre-dominant factor in this type of
metamorphism.
o Cataclastic Metamorphism: Metamorphism brought about by directed pressure
only, at the surface of earth as the temperature is low.
o Dynamo-Thermal Metamorphism: Rise in temperature with increase in depth
combines heat with stress that brings about changes in rock. Such metamorphism is
known as ‘dynamo-thermal metamorphism’.
o Plutonic Metamorphism: Stress is effective only up to a certain depth &
metamorphic changes at great depths are brought about by uniform pressure & heat.
Such metamorphism is known as ‘plutonic metamorphism’.
Physical Classification
 This classification is based on general structure of rocks.
 Rocks are of 3 types;
o Stratified rocks
3

4. STONES
o Unstratified rocks, and
o Foliated rocks
Stratified Rocks
 These rocks possess planes of stratification or cleavage & can be easily split along the
planes.
 Eg. Sedimentary rocks.
Unstratified Rocks
 Rocks are unstratified
 Structure may be crystalline granular or compact granular.
 Eg. Igneous rocks
Foliated Rocks
 Rocks have a tendency to split in a definite direction only.
 It is common in metamorphic rocks.
Chemical Classification
 This classification is known as ‘Scientific’ or ‘Engineering’ classification.
 3 types are;
o Siliceous rocks
o Argillaceous rocks
o Calcareous rocks
Siliceous Rocks
 In these rocks, silica predominates.
 Rocks are hard & durable & are not easily affected by weathering agents.
 Eg. Granites, Quartzite, etc.
Argillaceous Rocks
 In these rocks, argil or clay predominates
4

5. STONES
 Rocks may be dense & compact or may be soft.
 These stones are hard & durable but brittle.
 Eg. Slates, Laterities, etc.
Calcareous Rocks
 Calcium carbonate predominates
 Durability depends upon the constituents present in the surrounding atmosphere.
 Eg. Limestone, Marble, etc.
Sources of stones
 The stones are obtained from rocks.
 A rock represents a definite portion of earth’s surface.
 It is not homogeneous & has no definite chemical composition & shape.
 Two types are;
o Monomineralic – contains only one mineral (eg. Limestone, Halite known as Rock
salt)
o Polymineralic – contains several minerals.
 A ‘mineral’ – substance having definite chemical composition & molecular structure.
 It is formed by natural inorganic processes & such minerals, when combine, form rocks of
various types.
 Properties of rocks are governed by properties of minerals in the structure.
Rock forming minerals
 Few natural minerals form the bulk of rocks & these minerals are called ‘rock-forming
minerals’.
 Commonly found minerals in Igneous rocks are;
o Augite:
 It is also called Pyroxene.
 Resembles hornblende but is heavier than it.
 Forms octagonal crystals & changes to chlorite by hydration.
5

6. STONES
o Chlorite:
 Derived from decomposition of augite, biotite & hornblende.
 Green in colour.
o Feldspar:
 Many varieties, common – orthoclase, microline & plagioclase series.
 Orthoclase – whitish, grayish or pinkish in colour.
 Straight splitting mineral with tabular crystals & well-defined spaces.
 If in abundance, rocks disintegrate easily.
 Microline – deep green or flesh-red colour.
 Found along with orthoclase.
o Hornblende:
 Heavy, strong & durable, but brittle
 Colour – dark green or black
 Glassy luster & frequently occurs as 6 sided crystals having the appearance
of hexagons.
 Changes to chlorite when exposed to weather.
 Essential component of igneous rocks.
o Mica:
 Silicate of aluminum with potassium.
 Occurs in thin transparent laminate or plates
 Two types – Muscovite & Biotite (occur separately or simultaneously).
 Muscovite – white mica or potash mica
 It has light colour or colourless
 Biotite – black mica
 Contains iron & when exposed to weather turns to chlorite & loses elasticity.
o Olivine
6

7. STONES
 Colour – black, olive – green or yellow colour.
 Colourless if found in thin sections.
 Frequently changes to serpentine.
o Plagioclase:
 Series of feldspar – sodium aluminum silicate known as ‘albite’ to calcium
aluminum silicate known as ‘anorite’.
 It is multiple twinning & is an oblique splitting mineral.
o Quartz:
 Crystalline form of silicate usually colourless.
 Sometimes colour – brownish, pink or yellow due to presence of metallic
oxides in small quantities.
 Weather proof & resistant to acid except hydrofluoric acid.
 Common sand – variety of quartz
 Transparent crystal – rock crystal
 Compact translucent mass of quartz – rock crystal.
 Compact translucent mass of quartz – hornstone.
o Serpentine
 Resembles chlorite
 Colour – pale green or yellow
 Massive appearance
 Following are the commonly found minerals in the Sedimentary rocks;
o Calcite
 Chief constituent of sedimentary rocks but rarely found in igneous rocks.
 It is calcium carbonate CaCo3 & gives out carbon-di-oxide Co2 when attacked
by mineral acids.
 Generally colourless, but with presence of impurities may be yellow, brown or
red colour.
 Available in various shades.
7

8. STONES
o Magnesite:
 Occurs rarely in nature, chemical composition is MgCo3.
 It is harder & less soluble in water than calcite.
o Dolomite:
 It is available in various shades.
 Crystals are brittle, but stronger & heavier than calcite.
 Insoluble in water & its chemical composition MgCo3.CaCo3 – bicarbonate of
magnesium & calcium.
o Glauconite:
 It has no definite crystal formcolour – varies from yellow to green
 Insoluble in acids & ordinary water.
o Limonite:
 It has an earthy appearance.
 Colour – varies from yellow to reddish brown.
 Insoluble in water but soluble in acids.
o Gypsum:
 It is hydrated sulphate of calcium.
 Chemical composition CaSo4.2H20
 White in pure state but with impurities, it is tinted grey, reddish, yellowish or
black colours.
 Crystalline substance with poor solubility in water.
o Anhydrate:
 It is an anhydrous variety of gypsum.
 Chemical composition – CaSo4
 Colour – varies from reddish – white to grey.
 In contact with water for long-time, gets converted to gypsum with slight
increase in volume.
8

9. STONES
Texture of structure of a rock
 The arrangement of minerals forming a rock is known as its ‘texture’ or ‘structure’.
 Following are the different types of texture;
o Compact crystalline: Fine grains or particles are held together in a compact
crystalline form. Eg. Marble, Quartise, etc.
o Conglomerate: Grains are round & different sizes. They are cemented together by
some binding materials.
o Foliated: Arrangement of minerals is in the form of parallel layers.
o Glassy: Like glass without hiany crystal.
o Granular crystalline: Crystals are of similar size & are separate. Held together by
binding materials. Eg. Sandstone, Gneiss.
o Pisolitic: Grains are bigger in size (as large as peas)
o Porous granular: Grains are in the form of irregular minute particles. Rock of such
texture is not durable.
o Porphyritic: Crystals of one or more minerals are large & predominant.
o Vesicular: Indicated by small irregular cavities on rock surface.
Fracture of a rock
 The type of surface obtained, when a rock is broken, indicated its fracture.
 Fractured surface are mostly irregular & the fracture of a rock determines its texture.
 Following are the different types;
o Conchodial: Presents a set of concentric rings (e.g.) quartz, flint, etc. Corresponds
to glassy texture.
o Earthy: Resembles earth (e.g.) chalk
o Even: Fracture surface is more or less plane & denotes a crystalline texture.
o Fibrous: Fracture surface is in the form of fibers. (e.g.) asbestos.
o Hackly: Rough & broken surface with sharp edges.
o Uneven: Fracture surface is rough due to minute elevations & depressions. It
indicated granular texture.
9

10. STONES
Uses of stone
 Stones have been used in construction of buildings since ancient times.
 They form a basic material for cement concrete & bricks.
 Following are the various uses of stone;
o Structure: Used for foundations, walls, columns, lintels, arches, roofs, floors, damp-
proof structures, etc.
o Face-work: Adopted to give massive appearance to the structure. Walls are made of
brick & facing is of stones of desired shades. This is known as ‘Composite Masonry’.
o Paving: Cover floors of buildings, such as residential, commercial, industrial, etc.
Also adopted to form paving of roads, footpaths, etc.
o Basic material: Stones are disintegrated & converted to form a basic material for
cement concrete, murum of roads, calcareous cements, artificial stones, hollow
blocks, etc.
 Miscellaneous: Stones are also used for;
o Ballast for railways
o Flux in blast furnace
o Blocks in construction of bridges, piers, abutments, retaining walls, light hoses,
dams, etc.
 Stones are gradually losing their popularity as building material for the following reasons:
o Dressing of stones – tedious, laborious & time-consuming.
o Desired strength & quality are not easily available, esp. in plain areas.
o R.C.C & steel have proved to be stronger, less bulky, more durable & suitable for
present day construction.
o Structures constructed of stones cannot be easily designed as R.C.C or steel
structures.
Natural bed of stones
 Building stones are obtains from rock that have a distinct plane of division along which
stones can split easily.
 This plane is known as ‘Natural bed of stone’.
 For sedimentary rocks, the natural bed lies along the planes of significance. &
10

11. STONES
 For Igneous rocks, the natural bed is of little significance & is difficult to determine.
 Natural beds of stone can be detected by pouring water & examining the direction of layer
(with the help of magnifying glasses, if required).
 With respect to natural beds, the stones are placed in different situations as;
o Arches: In stone arches, stones are placed with their natural beds radial.
o Cornices, String courses: Stones are partially unsupported in such areas & hence
should be placed with direction of natural beds, vertical. For corner stones, stones
without natural beds should be adopted.
o Walls: Stones should be placed in walls with the direction of natural bed, horizontal.
Tests for stones
 Following are the tests for different properties of stones;
Acid test:
 A sample stone weighing 0.50N to 1.0N is taken & placed in a solution of hydrochloric acid
for 7 days.
 The solution is agitated at intervals & if its edges are sharp & free from powder – good
building stone.
 If edges are broken & powder is formed on surface, it indicates presence of calcium
carbonate – CaCo3, - has poor weathering quality.
 This test is usually carried out on sandstones.
Attribution test:
 Used to determine the resisting power of stones, used in road construction.
 Samples of stones of size 60mm & weight 50N are put in both cylinders of Deval’s attrition
test machine.
 Diameter of cylinders is 200mm & 340mm, resp.
 The cylinders are closed & at angle of 30° with horizontal.
 Cylinders are rotated for 5 hours at rate of 30 RPM
 Then the contents are taken out & passed through sieve of 1.50mm mesh & quantity of
material required is weighed.
 Percentage wear = loss in weight x 100.
11

12. STONES
Initial weight
Crushing test
 Used to determine compressive strength.
 Sample stone of size 40 x 40 x 40mm cube is finely dressed.
 3 specimens of such samples are used & are to be placed in water 72 hours prior to the
crushing strength.
 The load bearing surface is covered with POP or 5mm thk. Plywood & load is applied axially
in a crushing test machine.
 Crushing strength = Maximum load at which sample crushes
Area of the bearing faces of the specimen.
Crystallization test
 4 cubes of 40mm sizes are dried for 72 hours & weighed.
 Then they are immersed in 14% solution of Na2So4 for 2 hours, dried at 100°C & weighed
again.
 The difference in weight is noted & the process is repeated at least 5 times.
 Each time, the difference in weight is noted & expressed as a % of original weight.
 Freezing and Thawing test
 Specimen of stone is immersed in water for 24 hours & then placed in a freezing mixture at
-12°C for 24 hours.
 It is then thawed or warmed at atmosphere temperature in shade, away from wind, sun rays,
rain, etc.
 The procedure is repeated several times & behavior of stone is carefully observed.
Hardness test
 To determine hardness of stone.
 From the sample stone, a cylinder of 25mm ø & height 25mm is taken & weighed.
12

13. STONES
 It is placed in Dorry’s testing machine & pressed with a pressure of 12.5 N & rotated at
speed of 28 R.P.M.
 Coarse sand is sprinkled during rotation.
 After 1000 revolutions, specimen is taken out & weighed.
 Coefficient of harness = 20 – loss in weight in gm
3
Microscopic test
 Thin sections of stones are subjected to microscopic examinations, for the following
o Average grain size
o Existence of pores, fissures, veins & shakes
o Mineral constituents
o Nature of cementing materials
o Presence of any harmful substance
o Texture of stone, etc.
Smith’s test
 Presence of soluble matter in a sample stone
 Few chips or pieces of stones are placed in glass tube & water is filled in the tube.
 After an hour, it is vigorously shaken or stirred.
 If water is clear – stone is durable & free of soluble matter.
 If water is dirty – soluble earthy & mineral matter is present.
Water absorption test
 From sample of stone, cube weighing 0.50N is prepared & its weight is recorded.
 The cube is then immersed in distilled water for 24 hours & then removed from water & its
surface is wiped with damp cloth & weighed again.
 The cube is suspended freely in water & weight is recorded.
 Water is boiled & cube is kept in boiling water for 5 hours & then weighed after wiping
surface.
13

14. STONES
 The values obtained are then calculated to determine the % of water absorption of stone.
Qualities of a good building stone
 Following are the qualities or characteristics of good building materials.
o Crushing strength:
 Should be greater than 100N/mm2
o Appearance:
 Should be uniform colour, free from clay holes, spots of other colour bands,
etc.
 Face work: Light coloured stone of uniform colour preferred.
o Durability:
 Should be durable.
 Factors contributing to durability are: chemical composition, texture,
resistance to atmosphere & location.
 Stones to be arranged in a structure, such that, the natural bed is
perpendicular to the direction of pressure.
o Facility of dressing
 Stones – easily carved, moulded, cut & dressed.
 However, it’s in opposition to its strength, durability & hardness & hence to be
properly correlated in stone. (This property of dressing to be correlated with
other factors).
o Fracture:
 Should be sharp, even, and bright & clear with grains well cemented together.
 Dull, chalky & earthly fracture of stone – early decay.
o Hardness:
 Greater than 17 – stone used for road work.
 Between 14 to 17 – medium hardness &
 Less than 14 – poor hardness, not used for road works.
o Percentage wear: In attrition test,
14

15. STONES
 Wear is less than 3% - stone not satisfactory.
 Equal to 3% - stone just toreable.
 More than 3% - good building stone.
o Resistance to fire
 Shape of stone to be retained when exposed to fire.
 Free quartz expands suddenly at temperature less than 600°C.
 Limestone with heat till 800°C, beyond it is burnt.
 Sandstone with silicates resists fire.
 Argillaceous stone – poor strength, but resist fire.
o Seasoning
 Stones obtained fresh from quarry contain some moisture known as ‘quarry
sap’, which makes the stone soft.
 Hence, it is easy to work for dressing, carving, etc.
 The stones are then dried or seasoned for a period of 6 to 10 months before
used for structural work.
o Specific gravity
 Heavy stones – more compact & less porous & can be used for construction
of dams, weirs, retaining walls, docks, harbor, etc.
 Light weight stones are preferred for dams, roof coverings, etc.
o Texture
 Compact fine crystalline structure free of cavities, cracks or patches of soft or
loose material as they would be strong & durable.
o Toughness index: In Impact test –
 Toughness below 13 – stone is not tough
 Between 13 to 19 – stone is moderately tough
 Exceeds 19 – stone has high hardness
o Water absorption
 Stones should not absorb water more than 0.6 weight after 24 hours.
15

16. STONES
o Weathering
 It should be capable of withstanding various atmospheric effects such as rain,
frost, wind, etc.
Stone Quarrying
 Process of taking out stones from natural rock beds is known as ‘quarrying’.
 This is different from ‘mining’. In a mine, operations are carried out under the ground at
great depth & in a quarry; operations are carried out at ground level in exposed condition.
Site for quarry
 Availability of tools, power, materials & labour.
 Availability of site for dumping refuse.
 Proximity of transportation facilities.
 Drainage of quarry pit.
 Absence of permanent structures in nearby areas but availability of clean water.
 Geological data of the kind of rock at site.
 Quantity & quality of stones likely to be obtained.
Important conditions
 Examination of rock surface: No cracks & fissures should be present & planes for splitting
along should be identified.
 Layout: Layout of various stages of quarrying operation.
 Men & Machines: Proper co-ordination of both.
 Removal of top surface structural stability
Methods of quarrying
 Quarrying with hand tools.
 Quarrying with channeling machines.
 Quarrying by blasting.
Quarrying with hand tools
 Done in 3 ways:
16

17. STONES
o Digging or excavating
o Heating
o Wedging
 Digging or Excavating: Stones are excavated or dug by suitable tools as pick-axes,
hammers, shovels, chisels, etc.
 Heating: Top surface of rock is heated by pilling heap of fuel over it & setting a steady fire.
Due to heat & unequal expansion, the rock splits with dull bursting sound. It is then removed
using suitable instruments.
 Wedging:
o If rock surface contains cracks, steel wedges are placed in it & driven by hammers.
The rock surface splits & stone is removed using suitable instruments.
o If cracks are absent, they are artificially created using plug & feathers.
o Holes are drilled on the surface & a plug with feathers is placed.
o Plugs are driven in by hammers, which forces the rock to split.
o If rock is soft, wooden plugs can be used soaked in water. When wood swells cracks
occur on the surface of rock. It is employed for stones as laterite, marble, limestone,
sandstone, etc. – costly stratified rocks & comparatively soft & is preferred to
blasting, wherever possible.
Quarrying with Channeling Machine
 Channeling machines driven by steam, compressed air or electricity are used to make
vertical grooves or channels on the rock mass of sizes = length 2.4m, width 50mm – 75mm
& depth 2.4m – 3.7m.
 Channels are made around the block that needs to be split from rock mass & horizontal
holes are drilled beneath the block & then wedges are driven into holes to break loose from
its bed.
 Process is employed for marbles, limestone & soft sandstones.
 Possible to separate very large blocks from rocks.
Quarrying by Blasting:
 Explosives are used to convert rocks into small pieces of stones.
17

18. STONES
 This method is employed for quarrying hard stones, having no fissures or cracks & its main
purpose is to loosen large masses of rocks.
 Stones obtained are used for aggregate for concrete, road metal, ballast in railways, etc.
Tools for quarrying
 Process of blasting is important with respect to stone quarrying.
 Following tools are required in the process of blasting;
o Dipper: It is used to drill a hole to required depth.
o Jumper: It is used to make blast holes & is effective in boring nearly vertical holes.
o Priming Needle: It is used to maintain a hole for insertion of fuse after the hole is
filled with explosive & tamped earth. It is thin copper rod pointed at one end.
o Scrapping tool: It is used to scrap dust of crushed stone from blast holes. It is an
iron rod with circular plate on one end & a lop at other end to facilitate handling.
o Tamping bar: It is used to ram or tamp material while refilling blast holes. It is a
heavy brass rod of 10mm to 15mm dia. & tapers a little at the end.
Materials for blasting
 Detonators:
o It is a contrivance whose explosions initiate that of another.
o It is a copper cylinder of dia. 6mm & length 25mm, closed at one end & projecting
fuse at other end.
o It is used when dynamite is adopted as explosive.
o Detonators are fired either by fuse or electric spark.
 Explosives: Blasting powder & dynamite together are used as explosives.
o Blasting powder – also known as gun powder is a mixture of charcoal, salt petre &
sulphur.
o Dynamite consists of 25% sandy earth saturated with 75% of nitro-glycerin & is in the
form of a thick paste sold in cartridges.
 Fuses:
o These are used to ignite the explosives.
18

19. STONES
o They are in the form of a small rope of cotton coated with tar & a continuous thread
of fine gun powder.
o For electric firing, patented electrical fuses are used.
Process of blasting
 Blasting is carried out by hand drilling as follows:
 Blast holes of required depth & diameter are made using jumpers, dippers & scrapping
spoons.
 Water is added in small quantity at intervals to make the rock soft & convert dust to paste
which is then removed with scrapping spoons & blast holes are cleaned by rotating a small
iron rod with a rag tied at its end.
 Gun powder or dynamite is then placed inside the dried hole at the bottom & a priming
needle, a thin copper rod is place coated with grease.
 The remaining portion of the blast hole is filled in layers of dry sandy clay, moorum or ant-hill
earth & rammed hard each time, by a brass tamping bar.
 When tamping is done, the priming needle is frequently turned so that it can be removed
easily later.
 When tamping is complete, the needle is pulled out slowly, leaving a narrow hole which is
again filled with gun powder or dynamite.
 A fuse is then inserted in the hole & is kept projecting outside the hole for a length of about
600mm to 900mm.
 This forms a link between the fuse at top & charge of explosive at the bottom.
 The free end of the fuse is fired with a match or electricity.
 Using electricity has the following advantages;
o Ensures safety
o Saves time & labour
o Economical
o Useful for firing under water or in wet places.
o Avoid accidents & no danger of misfire.
o Blocks of small sizes are obtained.
Precautions in blasting
19

20. STONES
 Failure of explosion: Sometimes explosives fail. In such cases a new hole is drills close to
the previous hole (but not too close) & the process is repeated. Closeness of holes can
result in simultaneous blasting, causing accidents.
 Line of blasting: Gases formed during explosion try to escape through fissures, cracks,
faults or bedding planes, but if they cannot escape, they follow the line of path which offers
least resistance.
o Such a line is known as line of least resistance or LLR.
o LLR plays an important role in determining the quantity of explosive required in the
process of blasting.
 Needle and Tamper: These should be made of copper, brass or bronze but not steel as it
causes a spark when struck on the surface of rock, leading to premature explosion &
serious accidents.
 Notice of blasting: Notices & visible signs of red flags should be placed around the area of
blasting & fixed hours of blasting operations should be made known to public.
 Retreat to a distance: Whistles & sirens to be given for safety of workers & fuse adopted
for explosion should give time for retreating.
 Seepage of water: If water is entering the blast hole, the explosive should be placed in thin
iron plate or water proof paper.
 Skilled supervision: Work of blasting should be entrusted only to trained & experienced
persons.
 Storing: Explosives should be stored in specially constructed building known as ‘Magazine’
or ‘Store house’ with the following precautions;
o Torches should be used in case of power failure.
o Outsiders should not be permitted & authorized persons must wear magazine shoes
or shoes with no nails.
o Detonators should be placed separately away & all other explosives should be kept
in separate boxes.
o Magazine should be located away from residential areas, fuel storage areas, etc. &
firing & smoking should be strictly prohibited with 50m radius around the magazine.
o Loose or open wiring should be avoided in a magazine & explosives inside should be
handled gently.
o Under no circumstances, should any one approach the magazine during a thunder
storm.
20

21. STONES
o The magazine should be protected from lightning & lighting conditions, one at each
end of the magazine should be provided.
Dressing of stone
 Stones cut into suitable sizes & with suitable surfaces, after being quarried is known as
‘dressing of stone’ & is carried out for the following purposes;
o To get desired appearance from stone work.
o To make transport easy & economical from quarry.
o To take advantage of trained local men near the quarry
 Dressing can be divided into 2 types;
o Quarry dressing
o Site dressing
 At quarry place, the stones are first dressed roughly, as it is possible to get cheap labour,
sort out stones for different works, irregular & rough portions of stones are removed & also
facilitates easy transportation, stones can be dressed easily due to quarry sap & natural bed
of stones can be made prominent.
Types of finishes
 Axed finish: Surfaces of hard stones such as granite are dressed by means of an axe.
 Boasted or droved finish: Boaster – a chisel having an edge of width 60mm, is used to
make horizontal, vertical or inclined non-continuous parallel marks on the stone surface.
 Chisel – drafted margins: Margins, either square, pitched or chamfered are made to obtain
uniform joints in stone work.
 Circular finish: Surface of stone is made round or circular.
 Dragged or Combed finish: A drag or comb – piece of steel with a number of teeth is
rubbed on the surface of soft stones in all directions.
 Furrowed finish: A margin of 20mm width is sunk on all edges of stone & the centre portion
is projected for 15mm with a number of horizontal or vertical grooves of 10mm width.
 Moulded finish: Surface of stone can be moulded in any shape for appearance of work by
hand or machine.
 Hammer-dressed finish: Stones are made square or rectangular roughly by means of a
Waller’s hammer.
21

22. STONES
 Plain finish: Surface of stone is made approximately smooth with a saw or chisel.
 Polished finish: Surface of stones as marbles, granites, etc. can be polished either by hand
or machine.
 Punched machine: Depressions are made on the surface of stone as hollows & ridges
using a punch.
 Reticulated finish: A margin about 20mm wide is made on the edges of the stone &
irregular sinking are made on the inside space with a pointed tool to give a net-like
appearance.
 Rubbed finish: A piece of stone is rubbed on the surface or with a suitable machine with
the help of water & sand.
 Scabbling finish: Irregular projections are removed with a scabbling hammer & thus stones
are roughly dressed.
 Tooled finish: Stone surface is finished by means of a chisel & parallel continuous
horizontal, inclined or vertical lines.
 Self-faced or Rock-faced or Quarry-faced finish: Stones obtained from quarry have a
smooth surface & can be directly placed at work.
 Sunk finish: Surface is sunk below original levels as wide grooves, chamfers, etc.
 Vermiculated finish: Similar to reticulated finish, only difference being, the sinking is more
curved & gives a worm-eaten appearance.
Deterioration of stones
 Stones exposed to atmospheric & external agencies, cause their deterioration.
 Following are the causes;
o Alternate wetness & drying: Subjected to rain, water, frost, dew & the dried by
sunshine alternately.
o Frost: Moisture freezes in very cold places inside the pores of stones & causes the
stone to split due to increase in volume.
o Impurities in atmosphere: Impurities act on carbonate of lime & cause deterioration
of stone.
o Living organisms: Organisms make holes in stones & also secrete organic acids
thus weakening the stones.
o Movements of chemicals: Stones when placed above, minerals transfer due to rain
water etc. & cause decay.
22

23. STONES
o Nature of mortar: Mortar as binding material may cause disintegration to stone.
o Rain water: Two types of action – physical & chemical.
 Physical – alternate wetness & dryness
 Chemical – gases absorbed by rain water – CO2 & H2S.
 Temperature variations: Alternate expansion & contraction of stone due to increase and
decrease in temperature.
 Vegetable growth: Creepers & certain trees attract moisture & keep stone surface damp &
try to expand.
 Wind: Fine particles suspended in wind strike against surface of stone when forcefully blown
causing decay of stones.
Retardation of decay of stones
 Compact siliceous stones: Sandstone for external use & limestone or calcareous
sandstones with open textures to be avoided for external work. Preferable dense crystalline
texture.
 External rendering: Pointing & plastering to be done on the surface at the time of
construction.
 Joints: Solid structure without hollows or cavities.
 Natural bed: Stones placed in position with natural bed.
 Qualities of stones: Well-dressed stones instead of rough stones.
 Seasoned stones: Stones should be seasoned before use as they contain quarry sap.
 Size of stones: Large stones to be adopted as no. of joints are lessened.
 Washing with water: Surface of stone to be cleaned regularly.
Preservation of stones
 Ideal preservation should have the following properties;
o Should not allow moisture to penetrate
o Should not develop objectionable colour.
o Economical, non-corrosive, harmless, effective for a long-time & application on stone
surface is easy.
Types
23

24. STONES
 Coal tar: Preserve stone, but develops objectionable colour & absorbs heat. Thus not
adopted generally.
 Linseed oil: Can be raw or boiled. Raw requires frequent renewal but does not change
colour of stone. Boiled stays long but surface of stone becomes dark.
 Paint: Changes original colour of stone & applied under pressure for deep penetration.
 Paraffin: Used alone or with neptha, change colour of stone.
 Solution of alum & soap: Alum & soap (soft) dissolved in a liter of water & applied as
preservative.
 Solution of baryta: Barium hydroxide (OH2) applied as preservative.
Artificial stone
 These are also known as ‘Cast stones’ or ‘Reconstructed stones’.
 The procedure for making an artificial stone is as follows;
o The natural stone is crushed into 6mm sizes & stone dust is removed.
o A mixture of stones of sizes 3mm to 6mm, less than 3mm & cement is mixed in
proportion of 1½ :1½:1.
o Necessary colour pigment is added for desired colour.
o Water is added to this & all materials are mixed well.
o The mixture is then placed in special moulds & is allowed to harden.
o Artificial stone is ready in block form & polishing is done if required.
o White cement can be used in place of ordinary cement.
Forms of Artificial stone
 Cement concrete: Mixture of cement, fine-aggregate, coarse aggregate & water. It may be
cast-in-situ or pre-cast.
 Mosaic tiles: Pre-cast concrete tiles with marble chips at top surface, available in different
shades are ‘Mosaic tiles’.
 Terrazzo: Mixture of marble chips & cement. Used for temples, bathrooms, residential
buildings, etc.
Advantages:
 Cavities to convey pipes, electric wires, etc. can be kept in artificial stones.
24

25. STONES
 Grooves for fixing various fittings can be cast in them.
 Can be cast as a single piece or any desired shape. Hence trouble of getting large blocks
for lintels, beams, etc is avoided.
 It is stronger than natural stone & is cheap & economical.
 It is durable & can resist deterioration & disintegration of atmospheric agencies.
 Natural bed is absent & hence can be laid in any direction.
25