STONES:STONES:The stones which are suitable for theconstruction of the structures such asretaining walls, abutments, dams,barrages, roads etc are known asbuilding stones. Building stones shouldpossess enough strength and durability.Stones have been considered as one ofthe popular building material from theolden days due to their availability inabundance from the natural rocks.
COMMON USES OF BUILDING STONE:It is used in foundations of buildings,It is used in construction of dams, barrages, etc,In its crushed (powdered form) it is used as artificialsand,It is used as raw material for manufacturing of cement,In its broken form it is used as material for constructionof road and railway tracks,It is used as decorative material in buildings,It is also used as parts of buildings such as lintels andarches, etc,It is also used as thin slabs for building roofing,It is also used for ornamental works in buildings,In its broken form it is in the manufacturing of concrete,
CHARACTERISTICS OFGOOD BUILDING STONES:There are so manycharacteristics of good buildingstones, but some importantcharacteristics are given below.
(1) Hardness:Hardness denotes several qualities ofstones such as resistance to cutting andresistance to abrasion ( rub with eachother). Specially stones are used in case ofroads and railway tracks. To check thehardness of stones various tests areconducted in the laboratories. The moreimportant tests to check the hardness isLoss Angles Abrasion test. It depends uponthe nature of its constituent minerals.
(2) Durability:Durability is the power of stone to resistatmospheric and other external effects.It depends upon:Chemical composition,Physical structure,Resistance to weathering effects,Place where it is usedStone which contain silicates will be durablethan those stone which contain calcareoussubstances.
(3) Porosity and Absorption:Stone can hold water in two waysEither through porosity or absorptionFor building purposes, the better stones are thosewhich are less porous because they will absorbless moisture. Porous stones damaged easily.(4) Decomposition:Gases and acids in rain water dissolve someconstituents of stone and cause the stone decay.(5) Disintegration:In cold countries water freezes and expands andthus disintegrates the stones.
Reliability:When exposed to fire stone should be reliable (goodin quality).Weight:This is an important characteristic of stone. Itdepends upon the type of structure of stone in whichwe shall use.E.g. we shall use heavy stones in the construction ofthe dams, bridges, etc.Strength:It is power of stone to sustain pressure or resistanceto crushing force.Average crushing strength of stone is 3 tons persquare inch.
Appearance and color:Highly colorful stones are preferredfor architectural purpose but thoseare soft and thus less durable.Therefore, lighter stones arepreferred than to darker ones.Physical Strength:Crystalline structures are moredurable than non-crystalline structurestone.
Seasoning Qualities:A good building stone should have goodseasoning qualities. All the stones contain somemoisture which is known as quarry sap stones.The period 3-6 months are enough forseasoning.Fire resistance:A good building stone should be fire resistant.Some stones such as basalt and trap resist firevery well but some varieties of igneous andmetamorphic stones are very weak against fire.
EXAMINATION AND TESTING OFSTONES:It is very important to examine the stonebefore its selection for any particulartype of engineering structure. For thispurpose various types of tests are to beconducted to find out the suitability ofstone for engineering structure. Thereare so many tests but some importantamong them are as follows.
(1) Crushing test:For this test 04 cubic cm finely dresseddifferent samples of stones are used.Their type is made flat and horizontal andcovered with plaster of Paris. They aretested in a compression testing machine.The load must be applied axially and thechanges in the blocks at thecorresponding load are recorded. Theblocks or samples which bear more loadsare to be selected.
(2) Crystallization or weathering test:For this test 04 cubic cm different samplesof stones are first weighed and thenimmersed in a 14 % solution of sodiumsulphate (NA2SO4) at room temperature fortwo hours and dried at 1000C . They areagain weighed. This process of weighing,immersing in salt solution, drying and re-weighing is repeated for 10 to 15 times. Astone which is not much affected by saltsolution is supposed to have very goodweathering properties.
(3) Porosity and Absorption test:To ascertain the relative qualities ofdifferent stones, they are immersed inwater for 24 hours and the amount ofwater absorbed by each specimen isnoted. Greater absorption of water bythe stone means that it is porous andcan not resist weathering forces well.The test specimen which absorbs thesmallest amount of water is the best.
(4) Attrition test:This is the test to check the wear and tearof stone. To conduct this test differentangular pieces of stones are weighed andcharged into a cylindrical drum along withthe iron blocks provided. The drum is thenrotated at the rate of 30 to 33 rmp. About100 to 150 revolutions are made and the %age of wear is noted. The machine usedmay be Devals attrition machine. The stonewhich ears less is considered to be thebest.
(5) Acid test:This is the best test to find out the action ofacids on the stone. For this test about 50 to100 grams sample of stone is immersed in asolution of 1 % HCl or H2SO4 for about aweek. The sample being agitated (pressed,disturbed) at intervals. If the edges of stoneare retained and there is no deposition ofany loose particles on the surface, itindicates that the stone is good other wiseweak and bad.
(6) Smith’s test:This test is carried out to find out whether thespecimens possess crystalline structure.Small stone chips are kept for about half anhour in a glass of water filled to one third. Theglass containing the specimens and water ismoved quickly by giving it a circular motionwith the hand. If the specimen gives outearthy matter and water gets milkyappearance, it shows that the stone particlesare not properly cemented together.
(7) Hardness test:This test is conducted to find out theresistance of stone to abrasion. Thesample piece of stone is cleaned andrubbed by piece of rubbingmaterial/paper. The rubbed face of thestone is examined through a microscope.If marks of rubbing are visible, it showsthat the stone is soft and it can not beused for roads, pavements, etc.
(8) Fire test:For very important buildings, fireresistance of stone is also examined. Forthis test a small hut or a wall panel ofstone is built. One side of it is subjectedto 9500C and the behaviour of the stoneunder fire is studied. If the cracksdeveloped are deep. Then it should notbe used for important buildings.
(9) Microscopic test:This is a geological test in which a thin slice ofthe sample is examined through themicroscopic to determine the followingphysical properties of stone.The texture of the stone.The nature of the building materials/stones.The size, shape and nature of the individualgrains or crystals.The kind and nature of the mineral present.The presence of pores, if any.
DETERIORATION OF STONES:Deterioration of stone is the process of their breakingor their decay. Atmospheric agencies such as:rain,temperature,wind,frost, and living organisms, etcare responsible for their deterioration and theseagencies bring about physical and chemical changes inthe stones and disintegrate them. So, the stones whichcan resist the effect of all these agencies are said to bedurable. Some preservative materials which are usedto preserve the stones from deterioration are:coal tar, linseed oil, barium hydrate solution, alum soapsolution (mixture of alum and soft soap).By applying some of above preservative materials,stones can be preserved from the decaying.
CLASSIFICATION OF ROCKS (STONES) ORVARIETIES OF STONES:There are three main classes of rocks.(1) CHEMICAL CLASSIFICATION:Chemically stones are stones are classified intothree groups.(i) Argillaceous Rocks:Argillaceous or clay stones are those stones whichcontain (alumina Al2O3) (clay) as principalconstituent. These stones are less durable stones.All clay stones belong to this group.The examples of argillaceous rocks are Slate,Laterite, etc.
(ii) Silicious Rocks:The stones which contain (Silica SiO2) as principalconstituent are called silicious rocks. These stonesare durable stones.The examples of silicious rocks are granite, Quartziteand Sand stone etc.
• (ii) Calcareous Rocks:• The stones which containcalcareous material (CaCO3) asprincipal constituent are calledcalcareous rocks. They alsocontain some proportion ofsiliceous and clay matter.• The examples of calcareous rocksare marble stone and lime stone,etc.
(2) PHYSICAL CLASSIFICATION:Physically rocks are classified as:(i) Stratified Rocks:The rocks which are split into thin slabs orlayers easily are called stratified rocks. Allsedimentary rocks are essentially stratifiedand metamorphic rocks may be eitherstratified or unstartified depending upon itsparent rock.The examples of stratified rocks are Slate,Sand stone and Lime stone.
• (ii) Unstratified Rocks:• These rocks do not show sign ofstratification and can not be easily splitinto thin slabs or layers are calledunstratified rocks. All igneous rocks areessentially unstratified and metamorphicrocks may be either stratified orunstartified.• The examples of unstratified rocks areGranite, Basalt and Lime Trap.
• (3) GEOLOGICAL CLASSIFICATION:• Geologically stones are stones areclassified into three groups.• (i) Igneous or Primary Rocks:• These are primary rocks which are formedfrom molten magma. They representdifferent structural features dependingupon the condition of solidification andcomposition. Generally igneous rocks arestrong and durable.
(ii) Sedimentary or Secondary Rocks:• These are secondary rocks and areformed by the denudation and depositionof previously existing rocks due toweathering actions. Water (rain) is themost powerful and principal weatheringagent. The other destructive agents arefrost, winds and chemical actions. Thedestructive agents break up the surface ofearth which gets further broken up whencarried down by rains and rivers. Whenthe velocity of water in the rivers those
• (iii) Metamorphic or Tertiary Rocks:• Rocks which are formed due tometamorphic action of pressure or internalheat or by both (or) alteration of originalstructure due to heat and excessivepressure) are called Metamorphic Rocks.• Examples: Marble etc.
• QUARRYINFG OF STONES:• Stones are extracted from natural rocks indifferent sizes. The various methods whichare involved in the extraction of stonesfrom rock beds are collectively termed as“Quarrying of Stones”.• Open part of the natural rock from whichuseful material is obtained is known asquarry.• For this purpose particular rock is
• Methods of quarrying:• It is depending upon the rock and purposefor which it is to be used.• Commonly two methods are used forquarrying.• (1) Quarrying by digging• (2) Quarrying by blasting
• (1) Quarrying by digging:• This is done by three methods.• (a) By driving steel wedges intofissures:• Fissures, cracks, planes of cleavages areall weak points in the rock and by takingthe advantage of these weak points, steelwedges are driven in these naturalfissures or cracks, so that rock splitseasily.
• (b) By drilling artificial line of holes:• Some times line of holes (in rows) isdrilled with the help of chisel and hammer.Thus, the solidity of rock mark is dividedinto small portions and artificial fissuresare made. Steel wedges are driven inthese artificially made fissures. Then allthe wedges are hammered simultaneouslyand consequently the rock cracks alongthe face of holes.
• (c) By swelling hard wooden pegs:• Some times hard wooden pegs are drivenin either natural or artificially madefissures and are kept soaked with water.And in this way rock is splitted.•
• (d) Quarrying by blasting:• When the rock is very hard and unfissuredthen quarrying is done by blasting. Blastingis the process of loosening the hard andclosely packed material with the help ofexplosive materials. Various explosiveswhich are used for blasting purposes are:• Gun powder or black powder• Dynamite• Cordite Detonator• Fuses
But mostly two explosives are used whichare gun powder and dynamite. Where gunpowder is the mixture of potassium nitrate,charcoal and sulphur and dynamite is themixture of nitroglycerine.There are four main operations are involvedin blasting.•Boring hole in the rock•Charging with the explosives•Tamping•Firing.
• DRESSING OF STONES:• Dressing of stones is a process in whichtheir surfaces are prepared to a form, fit tobe used for any constructional purpose.Dressing is according to the type of workand demand.• Purpose of Dressing:• To give them good looking.• To provide horizontal and vertical joints inthe masonry.• To make them fit, to be used for particular
• Methods of DressingRough dressing Fair dressingOR• Dressing at quarry siteDressing at construction site•• Scabbling Hammering Self faced,quarry faced Chisel TooledFluted Pointed• OR
• (1) ROUGH DRESSING OR DRESSINGAT QUARRY SITE:• There are three main methods of roughdressing, which are a sunder:• (i) Scabbling:• In scabbling only irregular angels aretaken off with a scabbling hammer andtherefore that dressing is called scabbling.• (ii) Hammer Dressing:
• (iii) Self faced, quarry faced (OR) Rockfaced Dressing:• In this type of dressing, stone are onlysplitted into either as face stones or ascorner stones and nothing special is done.
• (2) FAIR DRESSING OR DRESSING ATBUILDING SITE:• There are four main methods of Fairdressing, which are a sunder:• (i) Chiseled Dressing:• About one inch width on all the four sidesof the exposed surfaces of the stones ischiseled to give them a betterappearance. This work is done with thehelp of chisel made of cast iron.
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