building stones ii

Building Stones-II

Some common building Stones

• Igneous rocks by virtue of their texture and minerals present in them have the ability to take very good polish and thus are become increasingly popular for face work .

Granite

Granite• Granite is a plutonic igneous rock because it is

formed due to solidification of magma atgreater depth. It is holocrystalline and leucocraticrock because it is complete crystalline and lightcolored rock.

Minerals present in granite

• Granite is composed of only primary minerals.Among these, feldspar and quartz occur asessential minerals and common accessoryminerals are such as hornblende, biotitic.

Granite

Granite

Structure

• Granite is compact, dense, massive and hardrock. But mural joints occur in some, dividing therock into number of rectangular blocks,thereby facilitating the quarrying processes.

Texture

• Granites typically exhibit an interlocking,coarse grained texture. Granites are usuallyequigranular. But some shows inequigranular,textures and are called granite porphyries.

Granite

Appearance of Granite

• Granite is generally medium to coarsegrained and grayish or pinkish in color.

Mode of Occurrence and relative abundance

• Granite rock occur in the form of very largeigneous bodies such as batholiths, stocks,often they occur as cores of mountainsranges and are thus related to mountain-building activity.

Granite

Granite

Physical properties of Granite

• Granite is massive, unstratified and dense,therefore it is very strong and competent

• Granite has an interlocking texture, which keepsminerals firmly held and this cohesion contributesgreater strength.

• Granite is either equigranular or has porphyritictexture.

• Since granite is massive and formed from melt itis neither porous nor permeable. So nosaturation or percolation by water is possible.


• Granite is very rich in silica; therefore it is very

much resistant to decay

• Presence of mural joint permit easy quarrying

• Presence of rift and grain permit easy dressing.

• Granites have the ability to take superb polish, and

hence are becoming increasingly popular for face

works of construction.

• Granites offer reasonable fire and frost resistance,

because minerals are not many and these rocks are

free from fractures.

Basalt

Basalt

• The term basalt was first used by pliny to refer a black,

ferruginous rock. Now the term is applied to very fine

grained, black volcanic rock in which plagioclase feldspar

and mafic minerals occur approximately in equal amounts.

Minerals

• Basalt is a simple mixture of Labradorite, augite(essential)

and iron oxide. It is similar to dolerite in mineral content.

Biotitic and hornblendes are the other rare accessory minerals.

Structure and texture

• Vesicular and amygdal structures are the most common in

basalt. Columnar structures and flow structure are also

observed in some cases.

Basalts

Basalts

Availability and mode of Occurrence

• Basalts are the most abundant among volcanic rocks. Theirquantity is five times greater than all other volcanic rocks puttogether. They occur as flat or slightly inclined lava flow.

Properties and Uses

Massive basalts are highly durable and the strongest. This isbecause not only they are compact, hard and tough but alsomore fine grained than dolerite. For this reason basalts areextensively used as building stones.

As a road metal, the basalts are excellent for macadam andbitumen roads. They are hard, tough and wear-resistingand have good binding properties.

Limestone

Limestone

• Among the sedimentary rocks, in the order ofabundance, limestone rank third, next to shalesand sandstones. These comprises 5 % of allsedimentary rocks occurring on the earth’ssurface.

• Limestone are typically non-detrital rocks. Theyare formed either chemically, due to precipitationof calcium carbonate from surface water. Ororganically, due to accumulation of hard partof organisms

Limestone

Limestone

• In hand specimens, limestones show different

colors like white, gray, buff, yellow and black.

• If the limestone have formed out of chemical

precipitation, they are extremely fine grained.

In case of organic, limestone have formed out

of chemical precipitation, they are extremely

fine grained. In case of organic, limestone, the

grain size may vary depending on the type of

organisms responsible for its formation.

Limestone

Limestone

Types of limestones

• Massive compact fine grained limestones withgrey or any other light color are common innature the porous types are yellowish, brownishetc.

• The other important types are

• Chalk, stalactites, stalagmites and drip stones,travertine, kankar, fossiliferous or shelllimestone, flaggy limestone, lithographiclimestone, magnesium limestone, argillaceouslimestone, siliceous limestone.

Limestone

LimestonePorosity and permeability• Limestones are the most deceptive and most

unpredictable rocks in terms of porosity andpermeability. This is because of the inherent characterof limestone, that is getting corroded by carbondioxide, bearing water at anytime. But inside theymay have solution cavities and solution channels ofvarying magnitudes. Highly irregular and uneventopography formed this way in limestone region isknown as Karst topography.

• Thus the range of porosity and permeability isunreasonable large in limestone. Therefore they areeither one of the best or worst aquifer in nature.

Limestone

Civil Engineering and Other Uses

• Massive and compact limestones are

reasonable competent to support civil

engineering structures. They are suitable as

road metal, railway ballast and as construction

material but may not be very durable.

Further if hollow, their load-bearing

strength also will get reduced.

Limestone

Marble

• The term marble is derived from marmore “ashining stone”. Like quartzite, marble is also aparametamorphic rock. It is a calcareousmetamorphic rock formed out of the thermalmetamorphism of limestone. Though it is notvery hard or strong it is the most valuable rockoccurring in nature. Its value is due to its pleasantcolor, good appearance, easy workability,charming translucency and the availability totake brilliant polish. It is also valuable because itis not abundantly available in nature.

Marble

Marble

• Marble shows the following properties

• Color: Some marbles show uniform colorthroughout the rock. Pure marble is milkywhite in color. Pleasant shades of green, yellow,brown, blue or grey color may also occur.

• Grain Size: Fine medium or coarse grained, butthe rock is equigranular.

• Texture and structure: Marble shows a typicalgranulose structure. This is because calcite,which is neither platy nor prismatic, is the mostpredominant mineral of the rock.

Marble

Marble

• Hardness: Marble is relatively soft and is easily scratched

with a glass piece or penknife. For this reason, marble can be

conveniently cut mechanically.

• Appearance: When a hand specimen of polished marble is

turned around, a twinkling appearance is noticed because

the surface of the rock passes through cleavage planes, it is

reflected giving a twinkling appearance.

• Translucency: Pure white marble are reasonably

translucent, which is an additional virtue of marble.

• Mineral Present: Just as quartz is the most predominant

mineral constituent of quartzite, so is calcite in marble.

Marble

Properties and Uses of Civil

Engineering Importance• Occurance: As a geological formation, marble is found in

the form of thick or thin beds in association with othermetamorphic rocks like gneiss, schists and slate.

• ‘as already mentioned, marbles are well known for theirbeautiful colors, pleasing appearance and easyworkability. Being denser and less porous, it is of course,stronger than limestone. Marbles occurring in nature arequarried, dressed and used as building stones fortemples or other construction. Marbles provide aestheticbeauty and a pleasing appearance to the construction. Theyare used in innumerable ornamental, decorative andmonumental works where carving, engraving andpolishing etc are involved.

Marble

Sandstones

Sandstones

• Among sedimentary rocks, sandstones arevery abundant and are next only to shales inthis respect, they represent nearly 15 % ofthe sedimentary rocks of the earth’s crust.These are very common clastic rocks made upof sand and are described as arenaceous rocks.Unlike conglomerates, sandstones arestratified and sometimes fossiliferous too.

Sandstones

Sandstones

• Sand grains in sandstone are mostly quartz, Inaddition to these the other minerals are mica, magnetiteand feldspar.

• Nature of Sand Grains and Cementing Materials

• Based on the size of sand grains the sandstones may becoarse grained, medium grained or fine grained. Butgenerally the sand grain in any sandstones will benearly of the same size.

• The sand grain present may be rounded or surroundedor angular in shape.

• Sandstones occur in different colors such as white, red,yellow grey and green. The color of sand grain is dueto cementing material.

Sandstones

Sandstones

Porosity Permeability and Uses

• By virtue of their mode of formation, like

conglomerates, sandstones also generally

porous and permeable. The porosity of

sandstones is dependent on the size and shape

of the sand, Further the degree of cementing

also contribute to the porosity. Therefore

sandstones vary considerable in their porosity

and permeability.

Sandstones

• From the civil engineering point of view,however, careful study is necessary beforeconsidering a rock as competent or incompetent,useful or useless. When sandstone isconsiderably porous and permeable i.e.. whenthe degree of cementation is less, it will notmake up a good rock. & if the sand stone are wellcemented and if the grains are angular and quartzin composition, the siliceous sandstone are thebest and highly satisfactory for all civilengineering purpose.

Sandstones

Gneiss

Gneiss

• Among different metamorphic rocks, gneiss ismore widespread and abundant than others.

• Gneiss is a general name given to anymetamorphic rock which shows a gneissosestructure. In many cases, gneisses are derivedfrom granites. Hence, the minerals composition,grain size, color, etc, will be more or lesssimilar both in granite and gneisses. For thisreason, it is commonly referred to as granitegneiss.

Gneiss

Gneiss• A few details of its physical description are as follows

• Diagnostic character: Foliation Present

• Color: different shades of gray and pink, but generallypale colored.

• Grain size: Medium to coarse grained

• Texture and structure: Generally equigranular, butsometimes porphyroblastic. Foliation i.e.. alignmentof minerals is characteristically seen.

• Minerals Present: Feldspar and quartz usually makeup the bulk of a gneiss.

Gneiss

Gneiss

Origin

• Gneisses are usually formed out ofdynamothermal metamorphism of granite,sandstones and conglomerates, etc. Amongthese, granite gneiss is far more abundant thanall others.

Occurrence

• Due to close mineralogical and otherresemblance, granite gneisses may be treated asvarieties of granites themselves.

Gneiss

• As gneiss is a silica-rich rock, it is durable

• By virtue of mineralogical similarity to granite,gneisses also have pleasing color

• Gneiss is reasonably non-porous and impermeable,contributing to its strength.

• The gneissose structure with its alternating bands ofcontrasting colors on polishing, produces a very goodappearance.

• The foliation, to some extent, improves theworkability of gneiss.

• The occurrence of gneiss in plenty, in many places,makes it an important building stone or material

Gneiss

Laterite

• It is a Sedimentary rock composed of mostly of oxides of aluminiumwith varying amounts of oxide of iron.

• Texture and Structure

• The rock is formed from chemical decomposition of alkaline igneousrocks by leaching of some components. This results in Spongy structureand porous texture.

• Building Properties

• The Laterites are light to dark red in color depending upon thequantity of iron oxide in their composition. They are poor incompressive strength, which varies from 20- 30 kg/cm2.

• Laterite are used only in ordinary construction and mostly as road metalrather than building stone.

• Indian Occurrence

• Latterite are found in Maharashtra, Madhya Pradesh, Bihar, Orissa,and also in some southern states like Andhra Pradesh, Madras, and Kerala.

Laterite

Slate

• Slate is a dense, fine grained, argillaceous,parametamorphic rock. It has the uniquecharacter of slaty cleavage. It is formed out ofdynamic or regional metamorphism of shale. Byvirtue of its cleavage character. It is formed outof dynamic or regional metamorphism of shale.By virtue of its cleavage character, it splits easilyinto very thin sheets or slabs of considerable size.Extreme fine grained size, absence of reactionwith acid, slaty cleavage and shining on surfacesare diagnostic character of slate.

Slate

• Physical properties of slate are as follows

• Color: Slate usually exhibit uniform color. Generally,they are black or dark grayish black. But other colorslike brown, red, green and grey and yellow occurs.

• Grain Size: Slate is very dense looking and extremelyfine grained. Individual grains are too fine to be seenfrom the naked eye.

• Texture: Foliation is clearly visible through constituentminerals are fine and unrecognizable. The layers ofshale which are differently colored appear as ribbons orbands in slaty formation in fields.

Slate

• Bedding and fossil content: Some slate retaintheir bedding or lamination character of shaleas a relict feature. Fossil may occur rarely butsuch fossil are often distorted and squeezed out oftheir original shape.

• Hardness: Slates are relatively soft whencompared with other metamorphic rocks.

• Minerals Present: Slates are mainly made up ofsecondary mica and quartz other mineralswhich may occur are biotite, talc, feldspar etc.

Slate

Origin

• The majority of slates are the result of dynamic

metamorphism of argillaceous sediments. A

few slates may also be formed from altered

basic igneous rocks.

Properties and Uses of Civil

Engineering Importance

• Slates are dense, fine grained, impermeable andrelatively resistant to decay. However, sinceslates are soft and incompetent, they cannotwithstand great loads. So they are not suitablefor foundation purposes. Due to cleavagecharacter and softness, they split easily. Hencethey cannot be used as building stone. But sinceslates are impermeable and can be split into thinbut big slab of uniform thickness, they can beconveniently used for roofing, flooring, mantleand shingles etc. they can also be used asshelves.

Qualities Required In Stones

1. Strength

• For ordinary types of stone-houses, any

good rock being traditionally used for the

same purpose will normally possess

sufficient strength to bear usual loads. But

engineer must satisfy himself about all the

strength parameters only after through testing

in accordance of codes.


• Compressive Strength

• It is the main quality of a building stoneexpressed as the maximum load per unit areaat which the stone starts breaking.

• This property can be easily tested in a civilengineering laboratory on the UniversalTesting Machine ( U.T.M)

• The compressive strength of most commonlyused stones has been found to be 280 – 2800kg/cm2


Traverse Strength

• It is the resistance offered to a bending

loads. In the case of building stones it is to

be evaluated only when the stone is to be

used as a beam or lintel. This property is

commonly determined as modulus of rupture R

the R value for various stones vary between

20 – 300 kg/ cm2


Shear Strength

• Stones of good quality are often used as

piers and columns, especially in

monumental buildings. In Such Situations,

the stone is to withstand shear type of loads.

Hence it must posses sufficient strength.

• The shear strength of common buildings

stones lies between 70 – 160 kg/ cm2


2. Hardness

• “Hardness of stone may be defined as its capacity toresist scratching or abrasion”

• The hardness of stones depend on mineralcomposition. The significance of this property lies inits resistance to wear and tear during its use inwhere rubbing action due to natural agencies or byartificial causes such as in flooring is involved thusstones facing the prevalent sand laden winds in an areashould be chosen with great care as soft stones may beworn out most easily and quickly then expected.


3. Toughness

• Is a property related to both hardness and

strength. It is defined as the capacity of

stones to withstand the impact loads.

• Thus stones to be used in foundations under

heavy machines when vibration may be a

common phenomenon may not only be hard

and strong but very tough also.


4. Water Absorption

• Building Stones are liable to come in contactwith water used in foundation and exteriorwalls. Ideally, they must not absorb moisturebecause can become cause of many troubles.Water absorption may be defined as ‘Quantity ofwater absorbed by a stone till saturation’ waterabsorption is especially significant when a stoneis used in foundations in cold climate wherefreezing temperature is a common phenomenon.


• In such situations water within the pores may

freeze and exerts disintegrating stresses.

Disintegration of stones by freezing water is

known as frost action. And this process may

spoil porous stones used on outer surface or

as costly buildings unless they are protected

from rains.


5. Appearance

• Stones are available in almost all colors from milkwhite to blood red to pitch black. Naturally,appearance of a stone for a building becomes animportant factor for selection.

• Taj mahal at agra was constructed with white marblealthough red and green or pink marble are available.For red fort in Delhi, the red color sand stone was usedto indicate royalty.

• Aesthetically light color are preferred in the exteriorof the building. Appearance have no significancewhen the stone is used in obscure positions such asin foundations.


6. Workability

• Stones when obtained from their natural place of

occurrence- the outcrops are quite irregular

masses. They require a lot of work on them before

they can be converted to appropriate shapes for used

in construction. Shapes required may vary from

ordinary rectangle to square block of small sizes.

The process of giving a proper shape dimension

and surface finish to a raw stone before it is fit for

use in construction is called dressing .


• It has been observed that all the stones cannotbe dressed or worked easily. The cost ofdressing stones per block may become animportant factor in selection of stones.

• Igneous rocks like basalt and granites arevery difficult to dress and polish. Marbleand limestone however are comparativelysoft and can be given any shape, finish andpolish at comparatively low cost.

Qualities required in Stones

6.Durability

• It denotes the period in years for which a stonemay stand practically unaltered after beingused in construction,

• A durable stone must

• Withstand load

• Must keep the original appearance

• Must resist the effect of cold and heat

• Must not suffer deterioration and decomposition bygases and surrounding industries.

Qualities required in Stones

• Obviously the durability of stone does not depend ona single property but rather a set of propertiesdiscussed above.

It may be summarized that a stone will be durable when :

• It has high strength for designed loads

• It has uniform close packed and dense structure withvery low absorption value

• It is made up of vey hard and resistant mineralconstituents

• It is resistant to chemically reactive gases such assulphur dioxide, carbon dioxide etc.

Deterioration and Preservation of

Stones

• Stones, like all other materials used in

construction, deteriorate with time. Some

undesirable changes are likely to develop in

them after years of exposure to natural

agencies like wind, water, and temperature.

Appearance gets definitely affected.

Strength qualities may not be easily affected

with time, but when they do, the durability

and safety of the building get endangered.


Stones


Stones

Causes of Deterioration

• There may be either physical or chemical or

both in nature.

Physical Causes

• Among these, the frost action, temperature

effect and the rubbing action of winds may

be quite significant.


Stones


Stones

(i) Frost Action

• In Cold Humid Climates, porous stones may

absorb moisture from atmosphere quite easily.

When this happens in winters, water within the

pores freezes and expands exerting tensile

stresses from within. This nature slow and steady

process, called frost action is repeated winter after

winter. Frost action is capable of Splitting and

Spalling on the surface of Stone.

Frost Action


Stones(ii) Temperature Changes

• Stones like all other materials expand on heating andcontract on cooling. Their Coefficient of expansion, is ofcourse negligible when considering on short term basis. Butwhen considered for many scores of years and especiallywhen stone are made of different minerals havingdifferent expansion and contraction coefficients someminor stresses do develop within the stone exposed toheating action of the sun.

• The Surface of stones start getting affected, apparentlyinsignificantly in the beginning. The effect deserves dueconsideration when stone are used in arid region on theexterior portion


Stones


StonesWind Action

• Strong winds rich in sand and dust particles act asvirtual sand papers. These are capable of polishing ofstones when they have a uniform texture and composition.But when the stones are made up of mineralsconstituents of different hardness, the soft mineralsconstituents of different hardness, the soft minerals getpolished more and more and may be gradually removedby pitting. The adjoining mineral may also fall apart onlosing the grip. Hence a process of slow physicaldisintegration starts on the surface of the stone exposed towind action.

• Wind action is a powerful scabbing process in areas ofstrong winds lying on the borders of deserts.

Wind Action


StonesChemical Causes

• The atmospheric moisture and some of the atmospheric gasesand vapors emanating from the industries are quite harmful formany types of stones exposed to their direct attack.

• (i) Water Vapors

• Water on chemical combination with atmospheric carbondioxide makes carbonic acid. This acid has mild corrosive actionon some stones. Thus it can slowly attack and eat up the strongest ofrocks

• (ii) Limestone and marbles

• Are both composed of calcium carbonate ( CaCO3). InIndustrial towns where SO3 vapors are emanated from manyindustrial chimneys, they mix with atmospheric moisture andmake an injurious sulphuric acid. The acid reacts with carbonateof the stone converting that into a sulphate and in the processtarnishing the surface of the stone.


Stones


Stones

• The so hot debated controversy of threat

deterioration to the marbles used in Taj

Mahal from the sulphate emanation Mathura

Refinery are based on the this basic fact.

Preservation of Stones

• It is quite possible to protect the stone from quickdeterioration by adopting one or more of thefollowing methods:

Careful Selection

• While selecting stones in a given area, a generalassessment about the weathering resistance of thestone can be formed from quarries, old exposure orfrom the stones used in the buildings. If a stone hasshown too much deterioration at those places, it islikely to deteriorate in a similar manner when used in abuilding construction in a new building. Hence it maynot be selected for use in similar situation exposed toweather.

Careful Selection


• Similarly, if a stone is to be used in an alreadyestablished or proposed industrial town, itscomposition must be given due consideration.Limestone, marbles and dolomites, all carbonatedrocks, are likely to deteriorate fast, especially onexposed parts. We should prefer use of siliceousstones like sand stone and quartzite instead.

• If the area has strong winds and located close todeserts, we should select only fine textured stoneshaving uniform composition and good hardness.E.g. quartzites instead of granites.


(ii) Careful Construction

• While constructing a stone house , in part or complete, a set ofprecautions can increase the life and beauty of the building to aconsiderable extent.

• Such as:

• Stones of proper size and shape should only be used with a mortar ofmatching quality so that no open spaces are left for moisture and gases toseep or get in.

• No ledge of stone should be left projecting out as it may act as agathering place for water during rains.

• Use of different stones in alternate layer or even in the same layershould be avoided. Homogeneity in the stone construction is considered abetter policy.

• Only well seasoned stones be used in construction, when stratified,their bedded planes should be given proper consideration while placingthem in load bearing position.


(iii) Application of preservatives.

• When a stone has already been used and there is a risk of its

deterioration because of environmental conditions, a preventive measure

may be taken by applying some well known preservative on it.

• A preservative is a oil or a paint or a solution which when applied on a

stone protects it from the direct attack of some deteriorating agency.

A really effective preservative must be

• Easily applicable

• Easily penetrating

• Unleachable

• Economical

• Further the preservative must not change the natural appearance of

the stone and produce odd smell


• A large number of preservative are available for preventingthe deterioration of stones. The following are mentionedbelow

Linseed oil

• It is used both in cold and boiled form. Boiled linseed oilwill change the appearance of stone to a darker shade.

Paraffin

• It is commonly used in the dissolved form in naphtha. Italso interferes with the original color of the stone.

Coal Tar

• It is cheap and effective preservative except it changesthe look of the stone.


Baryta Solution

• It is simply a solution of barium hydroxide and hasbeen found resistant against sulphate attacks onstone surface. It reacts with calcium sulphate formingbarium sulphate, which is more stable and protects thesurface of the stone from further deterioration.

Paints

• When stone deterioration has spoiled theappearance of a stone to a considerable extent, bestcourse would be to cover it with a paint. It will stopfurther deterioration and also improve the look.

Artificial Stones

Definition

• It is a stone like mass made by mixing together crushedstone pieces with cement and water in presence ofcoloring pigments .

Types

• Artificial stone in the broadest since of the term, may bebest called a type of cement concrete, this can be madein various shapes and in different composition. Thecomponent of artificial stones are decided by the engineerand pre-mixed proportions with cement and water. Afterthrough mixing, the paste is filled in proper moulds andallowed to set in. Thereafter they are removed andplaced on plain protected surface for curing andhardening.

Artificial Stones

Artificial Stones

• Grooves, cavities and hollow can be providedin the stone as desired at the molding stage.

• Terrazzo and Mosaic are the simple andcommon variety of artificial stones. In terrazzo,it is marble in the form of chips that is the mainmaterial used with the cement mix for making thestone.

• In the Case of tiles, it is the top surface of thenormal cement concrete in which marble chipsare spread uniformly during the castingprocess.

Terrazzo and Mosaic

Artificial Stones

Uses

• Artificial stones have the general propertiesand appearance of natural stones to someextent. These have the advantage that thesecan be casted and cured at the place of theiruse and in the any desired shape. Moreover,these stones often can be given any desiredpolish. For these reasons artificial stones areused in buildings to give decorative looks.

Artificial Stones

References

• Building Construction : Dr B.C. Punmia

• Civil Engineering Material : Prof. Singh

• Internet Web Sites

Thanks…