BUILDING STONE

Introduction :The earth’s crust is composed of rocks.

Rock is a mineral mass of a more or less uniform composition. It may consist of a single mineral (monomineralic) or of several minerals (polymineralic). Monomineralic rocks are quartz sand,

pure gypsum, and magnesite Polymineralic rocks are granite, basalt,

and porphyries

Natural rock materials are widely used for building purpose owing to their universal occurrence and physical and mechanical properties.

Rocks are the main source of material for the manufacture of mineral binding materials, such as gypsum, lime, cement and of artificial rock materials, eg.,brick, glass, items for concrete and mortar.

Classification of Rocks : The origin and conditions of rock

formation predetermine their chemical and mineralogical composition, crystalline structure and texture.

The three major classification are based on the following aspects :

(1) Geological or genetic classification (2) Physical classification (3) Chemical classification

(1) Geological or genetic classification

According to the geological classification, rocks are subdivided into three large groups, igneous rocks, sedimentary rocks, and metamorphic rocks.

(1) Igneous rocks : Cooling and hardening of

molten magma result in the formation of igneous rocks. Depending on the rate of cooling the sizes of crystals are formed.

Granite, syenites, diorites and gabbros have large crystals, while basalts, rhyolites and andesites have small crystals.

Igneous rocks are generally very hard.

(2) Sedimentary rocks : Transportation agents like wind, water and ice may move the loose weathered rock material and deposite them in the form of layers called sediments. Such sediments when subjected to heavy pressure undergo compaction and cementation, resulting in the Sedimentary rocks. Limestone, dolomite, shale, sandstone, etc., are sedimentary rocks

(3) Metamorphic rocks : Sedimentary rocks

and to some extent igneous rocks when subjected to changes brought about by the combination of heat, pressure and plastic flow ( called metamorphism) undergo changes in the structure, Texture and mineral composition, and this results in the formation of metamorphic rocks. Gneiss, schist, slate, marble, etc. are metamorphic rocks.

(2) Physical classification The basis for such a classification is the

physical properties of rocks, the manner and arrangement of different particles and mass forming a stone. They classified as follows:

(1) Foliated rocks(2) stratified rocks (3) Unstratified rocks

Foliated rocks :These rocks shows definite paeallel arrangement of minerals showing a tendency to split in a specific direction. Examples : metamorphic rock like gneiss, schist

Stratified rocks :Stratified structure is formed due to the splitting of parallel layers of sedimentary rocks. They exhibit distinct layers which can be separated. The plane of separation is called as a cleavage plane. Examples : Limestone, slate, and sandstone

Unstratified rocks : They are granular or crystalline structure and become solid and cooling. They do not show any sign of strata.Examples : igneous rocks like granite, basalt, etc.

(3) Chemical classification The presence of chemical constituents in the rocks is

the basis for their type of classification. they are as follows :(1) Argillaceous rocks(2) Siliceous rocks(3) Calcareous rocks Argillaceous rocks : In these rocks clay and alumina is the main constituents. Examples of the aegillaceous rocks are slate, laterite, etc.

Siliceous rocks:In these silica is the main constituent. The presence of the silica in the free state is called sand, and in the combined state is s silicate. Rocks containing silica in the free state are harder, and those found in the combined form are likely to be disintegrated. Examples of the silicate rocks are sandstone, quartzite, etc. Calcareous rocks Calcium carbonate or lime is the main constituents in these rocks. They are readily acted upon by dilute HCL Examples are limestone, marble, etc.

Properties of good building stone

Different civil engineering construction use stone. It is necessary to find their suitability under different condition. The following properties need to be examined before their use.

(1) Appearance and colour : Stones must look good in appearance

and be of uniform colour. Such a quality is essential for stone to be used for decoration work. Light coloured stones are preferred as they resist weathering action in a better way. Stones with iron oxide should not be used as the presence of iron oxide disfigures the stones and brings about disintegration.

(2) Strength : Stones are used as a

compression member and should have sufficient compressive strength. In general, all stones possess a reasonable degree of strength. The crushing strength of stone should be greater than 100 N/mm^2. igneous rocks have a strength of around 100 N/mm^2 and some of the metamorphic rocks also possess these strengths. But sedimentary rocks have a lower sterngth.

(3) Weight : in general, good building stones

should have a high weight to resist higher compressive forces. Good building stones must have a specific gravity greater than 2.70 . A heavy stone possess more compactness and less porosity.

(4) Hardness and Toughness : Stones must be

hard and tough so that they can resist wear and tear. Hardness is assessed by scratching and toughness by hammering. A good building stone should have a wearing resistance less than 3%, and if it is more than 3% it is not satisfactory. Stones used for road work should be hard to resist wear and tear.

(5) Porosity and Absorption : All stones

possess porosity. Stones that have a porosity over a certain percentage are unsuitable for building purposes. The presence of a higher percentage of pores may absorb rain, which may deteriorate the stone. A good stone should not absorb water more than 0.6% by weight. It must be capable of withstanding effects of atmosphere. If stones ina cold cli ate absorb water, they may freeze and even slt.

(6) Compactness : A good stone have a

compact, fine, crystalline structure and must be strong. A compact stone is capable of withstanding the effect of external agencies effectively.

(7) Fineness of grain : Stones that are fine

grained are suitable for moulding purposes. Such stones are easily carved and dressed. Non-crystalline structures stones are likely to disintegrate under the action of natural agencies

(8) Resistance to fire : Stones must be fire

resistant, i.e., they must retain their shape when subjected to fire. Limestone resists fire up to about 800 degree C. Sandstone can resist fire in a better way. Although argillaceous stones per poor in strength, they are highly fire resistant.

(9) Durability : Stones must be durable.

Basically, stones that have their natural bed perpendicular to direction of pressure are durable. Durable stones are those which are compact, homogeneous, acid resistant and have negligible water absorption.

(10) Dressing : dressing is the act of shaping

a stone for decorative purpose or for other purposes. For this, the stone should possess uniform texture and softness so that they may be easily dressed. Hard stone can’t be dressed

Types of building stones :(1) Granite : it is a deep-Seated igneous rock, hard,durable and available in different colours. It has high crushing strength &capable of sustaining highweathering.

(2) Basalt & trap : basalt and trap are also of igneous origin. These are effective solid rocks which have been formed on the earth’s surface in the absence of pressure by rapid cooling of the magma which also carries crystals of various minerals. These are hard, tough and durable and are available in different colours

(3) Limestone and chalk : These are sedimentary rocks which have been formed of remnants of seaweeds and living organisms consolidated and cemented together. They are easy to work and contain a high percentage of calcium carbonate.

(4) Sandstone : this is another form of sedimentary rock formed by the action of mechanical sediments. It shows a sandy structure which is low in strength and easy to work with the dress. This is available in different colours.

(5) Laterite : this is a metamorphic rock and is sandy clayey stone. It is porous and soft. It can be cut easily into blocks and contains a high percentage of iron oxide.

(6) Gneiss : it is a metamorphic rock which can be easily split into thin slab and easy to work on.

(7) Marble : it is a metamorphic rock which can be easily cut with a saw and can be curved.

(8) Slate : It is also a metamorphic rock which is black in colour and can be split easily.

(9) Gravel : It is available in river beds in the form of pebbles and is of different shape.

(10) Quartzite : it is a metamorphic rock which is hard, brittle and crystalline. It is difficult to work with and is very durable.

Uses of common building stone For foundation, walls, columns, arches,

lintels, roofs, floors, etc. For facing work of masonry. For railway as ballast. For concrete and road construction as

coarse aggregate For bridges as floors, piers, abutments,

retaining wall, etc. For lighthouses and dams.

Useful Building Stones In India

GraniteGranite is used for stone columns , road metal, ballast for railways, etc. It is found in Karnataka,Maharashtra,Rajasthan,Punjab,kerala. Sandstone

Sandstone is used for building and ornamental purposes and also as road metal . It is found in M.P., Rajasthan ,Tamilnadu etc.

-:Granite

Sandstone:-

Limestone It is used for flooring, roofing,pavements and in general building construction.It is found in Punjab Maharashtra,Andhra Pradesh,etc. Gneiss

It is used for flooring and pavement and not for major purposes because of its weakness.It is found in Karnataka,Gujarat and Tamilnadu. Marble

It is used for ornamental purposes,flooring,facing works,etc.It is found in Rajasthan,Gujarat and Andhra Pradesh.

-:Limestone

Gneiss:-

Marble:-

Quarrying Of Building Stones

Quarrying is the process by which stones are obtained from rock beds. Quarry is the place from which the stone is obtained.

Methods Of Quarrying1.DiggingIn soft rocks, stones are merely obtained by digging with the help of hand tools.like,chisels,pick-axes,hammers,etc.

2.HeatingThis method is adopted by burning certain kinds of fuels and the exposed surface of the portion of the rock to be separated .On burning several hours continuously due to unequal expansion of the rock, the rock gets separated from the mass with a dull noise.3.WedgingSoft stratified rocks can be removed by wedging as there rocks are in the form of layers and are easy to split. Soft rocks are removed with the help of pick axes an crow bars. Limestones, Marble, Slate are removed by this simple method.

4.BlastingThis technique is employed for quarrying hard and compact rocks. Blasting is done In some stages. Holes are made with steel bar with a knife-edged ends called jumpers or drilling machine. The drilled holes are charged with an explosive Of suitable capacity. Tempting of explosives is done before firing in order to prevent the blasting within the hole itself. The fuse is fired carefully. During the explosion, masses of stones around the hole are removed. A properly packed explosive shall produce a dull sound followed by displacing of the mass of rock around it.

Dressing Of StonesGenerally the stones obtained from quarrying have a rough surface and are irregular in shape. The process of bringing stones to a regular finish is known as dressing. The purpose of dressing are as follows:1.To set the stones in a regular shape and appearance.2.To prepare the stones for a suitable site for easy handling and transport.3.To secure proper bedding in stone masonry. Two types of dressing are in use, Quarry dressing Site dressing.

Durability Of StoneDurability of stones depends on the environment at which they are constructed. For proper durability assurance, it is necessary to know the agencies which deteriorate stones.Deteriorating Agencies Of Stones:1.RainRain is one among the main causes for wetness on stones. This wetness is dried by the sun. The process of wetting and drying causes deteriorating of stones.2.ClimateIn hot climate there are frequent changes in temperature which results in deterioration. SimilarlyStones exposed to cold climate causes freezing of

Water in pores resulting in the expansion, which causes splitting of stones.3.WindWind loaded with grit and dust strikes the stones and causes wear of the stones. Also moisture penetrate into the pores causes dampness resulting in deterioration.4.Vegetation GrowthVegetation growth along the cleavages of joints of stones release certain acids by the roots and thereby cause deterioration.5.ChemicalsChemicals of different kinds move and react due to the usage of different stone such as limestone and sandstone, thus causing deterioration.

6.Living organismsLiving organisms sometimes form In the joints of stones and cause instability to the structure . Further, these holes provide room for the accumulation of moisture and thereby deteriorate the stones.

Preservation of StonesPreservation of stones is intended to protect the structure against the action of weathering agents and also to protect the good appearance of the face work.This are the following ways to preserve the stones:1.Voids existing in the pores are filled properly.2.By coating with suitable oils like coal tar,linseed oil etc.3.By avoiding the moisture into the surface of the stones.4.Growth of plants on the joints of stones should be prevented.5.Building materials which are inactive with stones should be used.

Selection of stones for various works

1.General building worksStones used for foundation, walls and superstructure.Stone with high mechanical strength and the pleasant colors are widely used, such as sandstones.2.Building exposed to high windStones with a high crushing strength and the presence of silica in addition to hardness should be preferred, as such building are constructed near the sea or location where more wind prevails.

3.Building in industrial areasBuildings are mostly subjected to polluted atmosphere which may contain harmful gases, acids and moisture.These elements leads to damage, Hence stones that could sustain the effect of acidity and smoke on them are preferred.4.Building exposed to heat and fireStones that have high fire-resisting properties or stones which are free from calcium carbonate can resist fire.so,this type of stone can be used in buildings which are frequently susceptible to fire.5.Facing and architectural itemsFacing slabs and stones ,parts of stairs and landings ,parapets and guard rail are made of slabs split from natural stone and worked on.

6.Road metals and railways ballastsRoad metals and railway ballasts are subjected to high compression abrasion. Thus stones selected for such purposes should be able to resist thrust, must be strong and highly durable. Granite and quartzite preferred for such purposes.

TESTS ON BUILDING STONES

Buildings Stones must be tested to assess their properties to use for various purposes. Some Tests are simple which can be conducted in the field and some can be tested only in a laboratory. Accordingly they are grouped as • Field Tests• Laboratory Tests

Introduction

Simple Tests that can be performed on the stone because they are relatively simple. These include: A• Absorption Test• Smith’s Test• Toughness Test• Field Hardness Test• Acid Test• Crystallization Test

Field Tests

The test is carried out as follows: i. From the sample of stone, a cube weighing about 50gm is

prepared. Its actual weight is recorded as W1  gm. ii. Cube is then immersed in distilled water for a period of 24 hrs. iii. Cube is taken out of water and surface water is wiped off with

a damp cloth. iv. It is weighed again. Let the weight be W2 gm. v. Cube is suspended freely in water and its weight is recorded.

Let this be   gm. vi. Water is boiled and cube is kept in boiling water for 5 hours. vii. Cube is removed and surface water is wiped off with a damp

cloth. Its weight is recorded. Let it be  gm. From the above observations, values of the following properties

of stones are obtained.

Absorption Test

Percentage absorption by weight after 24 hours = 

Percentage absorption by volume after 24 hours = 

Volume of displaced water =  Percentage porosity by volume =  Density =  Specific Gravity =  Saturation Coefficient = 

This test is performed to find out the presence of soluble matter in a sample of stone. Few chips or pieces of stone are taken and they are placed in a glass tube. The tube is then filled with clear water. After about an hour, the tube is vigorously stirred or shaken. Presence of earthy matter will convert the clear water into dirty water. If water remains clear, stone will be durable and free from any soluble matter.

Smith’s Test

Rough Test without any rigid specification or procedure.

The stones is struck by a hammer to gauge the toughness of the stone. Force required to break the stone reflects the toughness of the stone

Toughness Test

Field Hardness Test Hardness is the resistance of a stone to

indentation, rebound or scratch. It is tested by a pen knife with the aid of

Moh’s scale of hardness.

Minerals Moh’s Scale Hardness test

Talc 1 easily scratched with the thumb-nail

Gypsum 2 scratched by the thumb-nail

Calcite/ Marbles 3not scratched by thumb-nail but easily cut by knife

Fluorite 4can be cut by knife with greater difficulty than calcite

Apatite 5 can be cut only with difficulty by knife

Orthoclase/ Feldspar 6can be cut with knife with great difficulty on thin edges

Quartz 7 not scratched by steel, scratches glass

Topaz 8  Sapphire/ Corundum 9  Diamond 10

Here, a sample of stone weighing about 50 to 100 gm. is taken. It is placed in a solution of hydrophobic acid having strength of one per cent and is kept there for seven days. Solution is agitated at intervals. A good building stone maintains its sharp edges and keeps its surface free from powder at the end of this period. If the edges are broken and powder is formed on the surface, it indicates the presence of calcium carbonate and such a stone will have poor weathering quality. This test is usually carried out on sandstones.

Acid Test

4 cubes of stone with dimension 40mm are taken. Stones are dried for 3 days and weighed. Then stones are immersed in 14% solution of Sodium Sulphate (Na2SO4) for 2 hours. After this stones are dried at 100 degree Centigrade and weighed. Difference in weight is noted .Process of drying, weighing, immersion and reweighing is repeated at least 5 times. Each time, change in weight is noted and it is expressed as a percentage of original weight.

PERCENTAGE OF WEAR SHOULD NOT EXCEED 2% FOR GOOD STONE.

Crystallization Test

These Tests are complex and require to be done in laboratories:• Attrition Test• Crushing Test• Impact Test• Laboratory Hardness Test• Microscopic Test• Freezing and Thawing Test

Laboratory Tests

This test is done to find out the rate of wear of stones, which are used in road construction. The results of the test indicates the resisting power of stones against the grinding action under traffic.

The following procedure is adopted:

i. Samples of stones is broken into pieces about 60mm size.

ii. Such pieces, weighing 5kg are put in both the cylinders of Devil’s attrition test machine. Diameter and length of cylinder are respectively 20cm and 34 cm.

iii. Cylinders are closed. Their axes make an angle of 30 degree with the horizontal.

iv. Cylinders are rotated about the horizontal axis for 5 hours at the rate of 30 rpm.

v. After this period, the contents are taken out from the cylinders and they are passed through a sieve of 1.5mm mesh.

vi. Quality of material which is retained on the sieve is weighed. vii. Percentage wear worked out as follows: Percentage wear = 

Attrition Test

Samples of stone is cut into cubes of size 40x40x40 mm. sizes of cubes are finely dressed and finished. Maximum number of specimen to be tested is three. Such specimen should be placed in water for about 72 hours prior to test and therefore tested in saturated condition.

Load bearing surface is then covered with plaster of Paris of about 5mm thick plywood. Load is applied axially on the cube in a crushing test machine. Rate of loading is 140 kg/sq.cm per minute. Crushing strength of the stone per unit area is the maximum load at which the sample crushes or fails divided by the area of the bearing face of the specimen.

Crushing Test

This test is carried out to determine the toughness of stone. This test requires an 'Impact Testing Machine'. In this test stones are filled in test cylinder of diameter 25 mm and height 25 mm. The cylinder is placed on machine and steel hammer of weight 20 N is allowed to fall on the specimen in cylinder. The height of first fall is 1 cm, height of second fall is 2 cm and so on. The height at which specimen breaks is recorded. If specimen breaks at 'n cm' then 'n' is the toughness index of stone.

Impact Test

For determining the hardness of a stone, the test is carried out as follows:

i. A cylinder of diameter 25mm and height 25mm is taken out from the sample of stone.

ii. It is weighed. iii. The sample is placed in Dorry’s testing machine and it is

subjected to a pressure of 1250 gm. iv. Annular steel disc machine is then rotated at a speed of 28

rpm. v. During the rotation of the disc, coarse sand of standard

specification is sprinkled on the top of disc. vi. After 1000 revolutions, specimen is taken out and weighed. vii. The coefficient of hardness is found out from the following

equation: Coefficient of hardness = 

Laboratory Hardness Test

The sample of the test is subjected to microscopic examination. The sections of stones are taken and placed under the microscope to study the various properties such as• Average grain size• Existence of pores, fissures, veins and shakes• Mineral constituents• Nature of cementing material• Presence of any harmful substance• Texture of stones etc.

Microscopic Test

Stone specimen is kept immersed in water for 24 hours. It is then placed in a freezing machine at -12˚C for 24 hours. Then it is thawed or warmed at atmospheric temperature. This should be done in shade to prevent any effect due to wind, sun rays, rain etc. this procedure is repeated several times and the behaviour of stone is carefully observed.

Freezing and Thawing Test

Types:• Cement Concrete Blocks• Artificial Marble• Terrazzo• Mosaic Tiles• Reconstructed Stone• Bituminous Stone

Artificial Stones

Constituents• Cement• Fine Aggregates• Coarse Aggregates• Water

Cast in situ or in Molds Can be precast with steel to be RCC

blocks

Cement Concrete Blocks

Constituents• Sand• Portland/Gypsum/Magnesite cements

Method 2:• 60:20:15 plaster in Powder, Pulverized

Marble,Potash Sulphate with 5% solution of glue and water

Mostly used in France

Artificial Marble

Constituents• Marble Chips• White Cement• Pigment

Precast or in situ Used in Residential

Buildings,Bathrooms,etc

Terrazzo

Precast Tiles Upper Surface made of Marble Chips Available in Different Sizes and Colours

Mosaic Tiles

Made From Debris of limestone quarries by Crushing

Mixed with Lime made from dolomite and heated in a closed retort up to 980˚C to drive out CO2

Slaked, Mixed with water and consolidated into blocks under Pressure.it is then dried and CO2 is admitted until Carbonization is Complete

Reconstructed Stone

Diorite and other Granite Stones are impregnated with prepared tar to form bituminous stones

Preferred where noiseproof,dustproof,wearproof stone surfaces are needed

Bituminous Stone

Can be used in areas where natural stone is costly or unavailable

Desired Shape and size is obtained easily Can be made in situ thus saving dressing and

transport cost Practically Defect Free Cavities can be made for wiring or plumbing

easily Weatherproof Strength is Design Based More Durable

Advantages of Building Stone

THANK YOUvatsal dalal

from,pandit deendayal petrolium university