Building Stones PDF

BUILDING STONES  CLASSIFICATION OF ROCKS Rocks Geological Physical Chemical Igneous Stratified Argillaceous Sedimentary Un-Stratified Siliceous Metamorphic Foliated Calcareous  GEOLOGICAL COMPOSITION -Igneou...

BUILDING STONES  CLASSIFICATION OF ROCKS Rocks Geological Physical Chemical Igneous Stratified Argillaceous Sedimentary Un-Stratified Siliceous Metamorphic Foliated Calcareous  GEOLOGICAL COMPOSITION -Igneous rocks (primary, un-stratified, eruptive) – cooled down molten volcanic lava (magma). Basalts and granites. – Sedimentary rocks (aqueous, stratified) – gradually deposited disintegrated rocks. Sand stones and lime stones. – Metamorphic rocks – transformed due to great heat and pressure. Granite to gneiss, lime stone to marble, shale to slate.  Examples of geological types of rocks 1.Igneous rock Vesicular basalt Red granite 2.SEDIMENTARY ROCK Limestone Sand stone 3.METAMORPHIC ROCK Gneiss Marble  PHYSICAL COMPOSITION ∞Stratified Rocks ∞Un-stratified Rocks ∞Foliated Rocks 1. Stratification is the layering that occurs in most sedimentary rocks and in those igneous rocks formed at the earth’s surface, as from lava flows and volcanic fragmental deposits. The layers range from several millimeters to many meters in thickness and vary greatly in shape. Strata may range from thin sheets that cover many square kilometers to thick lens-like bodies that extend only a few meters laterally. Rocks Having distinct layers which are separable. Cleavage Plane for split is easily visible. Example: Slate, Sandstone, Limestone. 2. Un-stratified describes rocks which are not completely stratified, and is applied to massive rocks, such as granite, porphyry, etc. and also to deposits of loose materials, such as the glacial till which occur in masses without layers or strata. Cannot be easily stripped into slabs. No sign of distinct strata. Example: Granite, basalt, trap. 3. Foliated repetitive layering in metamorphic rocks. It is any penetrative planer fabric present in metamorphic rocks. They have a tendency to split up only in a definite direction. Also known as S-taconite in sheared rock masses. Example: the bands in genesis.  Chemical Composition ► Siliceous – These are rocks mainly containing sand or silicates (SiO2). Consisting of quartz, sand, Granite, Basalt, etc. ► Argillaceous – These are rocks mainly containing Alumina (Al2 O3 ) and clay as the main components. Consisting of Clay minerals like slate and Laterite. ► Calcareous – Rocks containing Calcium Carbonate and Line. Consisting of Limestone, Marble and Dolomite.  QUARRYING OF STONES Quarrying: An art of extracting from the rock beds stones of different varieties used for general building work and broken stones for roads and concrete work, etc. quarrying is the only process/operation involved in production of natural stones. The open part of useful stones from the useful stone is obtained. Quarry: The place from stone is obtained by digging or blasting etc.  Selection of Quarrying Sites When selecting quarrying sites the following conditions are necessary: Sufficient Quality Proper transportation facilities Cheap local labour No problems of drainage of rain water Location of permanent structures in site of dumping refuse.  Methods of Quarrying Digging or Excavating Method - Stones occurring as detached nodules may be dug using manual methods like crowbars, etc. Heating Method – Rock surface is heated for several hours resulting into unequal expansion and crushing of rock into small pieces. The intermediate layer is heated electrically and the expansion separates it from the other two. Wedging Method - Layered rock is split at cleavage or seam using steel wedges and pins. In case of soft rocks, dry wood pegs are hammered into holes and water is poured over them. The wood swells and exerts pressure causing rocks to along the lines of the holes. The wastage is minimum and the slab of required size and shape can be quarrised. Blasting Method - Hard and compact rock is blasted out using explosives techniques comprising boring, charging, tamping and firing. Tramping – Tramping should be done very carefully otherwise the explosives fires back in the hole. Since the line of least resistance (LLR) is the shortest distance. From explosives in the hole to nearest rock face,  Methods of Quarrying Blasting Method Quarrying Tools Precaution to be taken during quarrying: Blasting should not be carried out in late evening or early morning. Blasting should be made public with sufficient time allowed to retire to safe distance. 200 m radius danger zone should be marked with red flags. First aid should be made available. Proper record of number of charges prepared, fired and exploded to account for misfires. Explosive should be handled carefully. Detonators and explosive should not be stored and kept together. Cartridges should be handled with rubber gloves. Maximum of 10 bore holes should be exploded at a time and that too successively and not simultaneously.  Explosives to be used in quarrying To meet the various conditions of quarrying, almost every class and grade of explosive is used. The explosives in general are: granulated powder containing 5 – 15 % of nitroglycerine ‘straight’ nitroglycerine dynamites ranging in range from 15 – 60% of nitroglycerine low freezing dynamites rated according to their equivalent percentage of strength with the ‘straight’ nitroglycerine ammonia dynamites rated in a similar way. In recent ways blasting with gelatin, gelatin dynamites, ammonium nitrate powders containing nitro- substitution compounds, chlorate powers and the so-called nitro-starch powders have been introduced in a small way in quarry operations.  Dressing of stone Pitched faced dressed – 2.5 cm edges dressed and made square Hammer dressed, hammer faced, quarry faced or rustic faced – dressed like a brick with 2.5 cm rough edges for use in masonry Rock faced and chisel drafted – chisel draft of 2.5 cm along edges Rough tooled – edges and corners made perfect square. Punched dressed – rough tooled improved up to 2 mm Fine tooled – fair smooth surface for ashlar masonry Dressed Stone Surfaces  Methods of dressing and polishing of stones  The stone are being dressed and polished so that we can preserve a completed stone work.  The stone is being dressed and polished by the following:  Linseed oil- raw linseed oil is light in color while boiled linseed oil is dark and hence discolor the stones.  Solution of alum and soap- they are dissolved in water and can be applied on the stone to act as a protective coating. Solution of barium hydroxide (baryta)- if the decay is calcium sulphate, then the treatment is effective. Paraffin- used alone or dissolved in naphtha as a paint medium. However it may changes the color of the stone. Paint- painting preserves the stone but changes the color of the stones. The paint should not react with the stone. Coal tar- even though it is listed as a preservative, it is a highly objectionable material to be used as it completely changes the color of the stone. It may not also suit some types of stones.  Artificial stones Definition - Building material made with cement, sand and natural aggregates of crushed stone for use in place of natural stone Properties Made with white cement, sand and natural aggregates of crushed stone Molded into most intricate forms Cast into any size Reinforced to desired higher strength Desired coloring may be achieved Desired finish may be achieved ► Concrete block - Cast in molds for steps, window sills, masonry work, etc. ► Ransom stone - Soda silicate plus cement for decorative flooring ► Victoria stone - Granite pieces immersed in soda silicate for two months ► Bituminous stone - Provide noise, wear and dust resistant stone surfaces  Imperial stone - Crushed granite plus cement, molded, steam cured Artificial marble - Pre-cast or cast-in-situ. Portland gypsum cement and sand. Cast blocks treated with magnesium fluorite, washed, paper wrapped, machine emery ground, polished and finally rubbed with ball of wool moistened with alum water Garlic stone - Iron slag and cement mixture molded into flag stones, surface drains, etc.  Advantages of artificial stones: 1. They can be cast as per the architectural requirements. Stones of any shapes and size can be obtained easily. 2. They can be made economical. Large concrete blocks are more economical than the natural stone blocks. 3. As natural bed is absent, placing them is more convenient than the natural stones and needs less supervision. Natural stones should be placed with their bed in compression. 4. No defect or cavity will be present as compared to natural stones. Hence, they are more durable. 5. They can be made in places where deposition of natural stones are not available as broken stones can be easily transported.  Tests on Rocks Selection of Sample for Tests A truly representative sample of grade of stone should be selected Sample may be selected from quarried stone or natural rock Separate samples weighing at least 25 kg each shall be collected from differing strata Test pieces for toughness or compressive strength test shall be at least 10.0 x 12.5 x 7.5 cm in size Test pieces shall be free from seams or fractures In case of field stones and boulders separate samples shall be selected of all classes of stones based on visual inspection 1.Simple Field Tests. Physical Tests On  Water Absorption Test: It is used to determine the presence of pores and extent of fluid absorption. Stones. This test should be done on all stones. In this test you put a sample of rock weighing about 50gm in distilled water and find the water absorbed in 24 hours. It should not exceed more than 0.6 %.  Smith’s Test: This test is used to determine the deterioration of stones when submerged in water. A sample of water is placed in a glass vessel and vigorously stirred and kept submerged for at least 24 hours. If the water becomes cloudy, the stone is good and durable. If the water turns muddy then the stone contains earthy substances. Some very consolidated stones look like simply slump under water in this test. We need to insure that all stones we use pass this test.  Toughness test: The test is to check the resistance to abrasion. Toughness is indicated by resistance to hammering. Hit the stone with a hammer and find how though it is to break with the hammer.  Moh’s scale of hardness test: A useful method of describing strength of stones is in terms of the hardness of the stone and it is done by scratching the surface of the stone with a pen knife and classify the hardness by Moh’s scale of hardness. – 1 Talc, scratched easily by thumb nail – 2 Gypsum, scratched by thumb nail – 3 Calcite, scratched not by thumb nail but by knife – 4 Fluorite, cut by knife with difficulty – 5 Apatite, cut by knife with difficulty more than 4 – 6 Orthoclase, cut by knife with great difficulty – 7 Quartz, not scratched by steel, scratches glass – 8 Topaz – 9 Sapphire – 10 Diamond  Acid test: This test is used to confirm the presence of poorly withering calcium carbonate articles in sandstone. The test is done by placing a cube of the stone weighing about 50 to 100 gm in 1% HCL acid for about 7 days. A good building stone should be free of powder formation on the surface of the cube and the sharp edges should not be broken up after the above immersion. This is basically to test weather resistance. Crystallization test: This test is to test the durability or weathering quality. A sample of stone immersed in solution of sodium sulphate and dried in an oven at 100 degree Celsius. The procedure is repeated five times and the loss if weight and the presence of cracking are noted. The ideal stone should not have any defect formed and the loss in weight should be minimal. 2.Laboratory Test  Attrition Test: Also know as abrasion test, determines the rate of wear of stones used in road construction. This is carried out in Deval’s attrition testing machine. Test details: 60 mm size pieces of sample stone weighing 50 N placed in two 200 mm and 340 mm cylinders of machine Cylinders rotated for 5 hours @ 30 rpm Contents sieved through 1.5 mm sieve, and material retained is weighed Percentage wear = loss in weight/initial weight x 100 Crushing Test: This test is used in finding the comprehensive strength of a stone cube 10mm in size in a compression testing machine. The rate of loading used is 140 kg per cm square per minute. Maximum load at which specimen crushes is the crushing strength per unit area (N/mm²) Freezing and Thawing Test: this test is useful in regions where the temperature can drop below freezing point. It consists of keeping a sample of stone immersed in water for 24 hours, then freezing the mixture at -12 °C. The sample is then thawed in shade at room temperature. Procedure repeated several times and behavior is noted.  Hardness test: This test is different from attrition test because here we use the Dorry’s testing machine. A cylinder od 25 mm of the rock is rubbed against a steel disc sprinkled with coarse sand. The sample is given a pressure of 1.25kg. After 1000 revolutions, the loss in weight is determined. Coefficient of hardness = {20 – (loss in weight in gms)}/3  Impact test: This test is for aggregates in concrete that undergoes impact as in runways in airports. Materials passing through 12.5 mm and retained as 10 mm are filled in the standard cylinder in three layers, each layer tamped with 25 strokes of an iron rod. A hammer weighing 14 kg is dropped from a height of 380 mm 15 times and the resulting material is sieved through a 2.36 mm I.S. sieve. The percentage fine is the aggregate impact test value. It should not be more than 45% for aggregates for concrete for ordinary use and not more than 30% for aggregates for concrete for runways and pavements. For Indian aggregates, it ranges from 15 to 30%. Blow height First blow – 1 cm Second blow – 2 cm Third blow – 3 cm nth blow – n cm nth blow breaking the sample has toughness index value as n  Microscopic test: In this test, thin sections of the stone are taken and placed under the microscope to study its grain size, mineral constituents and presence of harmful materials. Mineral constituents Texture of stone Average grain size Nature of cementing material Existence of fissures, pores, veins and shakes