Module 1 Notes 18cv34 PDF

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Building Materials and Construction

Module 1`

Module-1 Building Materials: Stone as building material; Requirement of good building stones, Dressing of stones, Deterioration and Preservation of stone work. Bricks; Classification, Manufacturing of clay bricks, Requirement of good bricks. Field and laboratory tests on bricks; compressive strength, water absorption, efflorescence, dimension and warpage. Cement Concrete blocks, Autoclaved Aerated Concrete Blocks, Sizes, requirement of good blocks. Timber as construction material. Fine aggregate: Natural and manufactured: Sieve analysis, zoning, specify gravity, bulking, moisture content, deleterious materials. Coarse aggregate: Natural and manufactured: Importance of size, shape and texture. Grading of aggregates, Sieve analysis, specific gravity, Flakiness and elongation index, crushing, impact andabrasion tests.

1.1

Introduction

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Materials which are required for construction of buildings are referred as building materials. Building materials are classified into three types Natural Materials: - These are naturally occurring materials namely wood, stone, mud or clay etc. Artificial materials: - These are man-made materials namely bricks, cement, glass & steel. Composite materials: - These are combination of two or materials namely concrete, plywood etc.

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1.2

Objective

• To study different types of building materials used for construction of buildings 1.3

Stones

Introduction Stones are naturally occurring building materials which is widely use in construction of buildings. Nowadays it has become an important source of aggregate (coarse & fine) for manufacturing concrete. Most of the historic monuments that remain even today are made of stones. These are permanent in nature and prices go up if you change the shape and texture of stone. Sources of stone are rock which is not homogeneous in nature, no definite chemical composition and shape. Therefore we can conclude, stones are one of the important building materials that all the Civil Engineers should be familiar with it.

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CLASSIFICATION OF ROCKS: Building stones are obtained from rocks occurring in nature and classified in three ways. Geological classification Physical classification Chemical classification

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I. Geological Classification: According to this classification, the rocks are of the following types. Igneous rocks: Rocks that are formed by cooling of Magma (molten or pasty rocky material) are known as igneous rocks. Examples: Granite, Basalt and Dolerite etc. Sedimentary rocks: these rocks are formed by the deposition of production of weathering on the pre-existing rocks. Examples: gravel, sandstone, limestone, gypsum, lignite etc. Metamorphic rocks. These rocks are formed by the change in character of the pre-existing rocks. Igneous as well as sedimentary rocks are changed in character when they are subject to great heat and pressure. Known as metamorphism. Examples: Quartzite, Schist, Slate, Marble and Gneisses.

Physical Classification: This classification based on general structure of rocks. According to this, the rocks are classified into three types a. Stratified Rocks: These rocks possess planes of stratification or cleavage and such rocks can be easily split along these planes Ex: sedimentary rocks b. Unstratified rocks: The structure may be crystalline granular or compact granular. Examples: Igneous rocks and Sedimentary rocks affected by movements of the earth. c. Foliated Rocks: These rocks have a tendency to split up in a definite direction only. Ex: Metamorphic rocks. Chemical Classification: According to this classification rocks are classified into three types. a) Siliceous rocks: In these rocks, silica is predominating. The rocks are hard; durable and not easily effected by weathering agencies. Ex: Granite, Quartzite, etc. b) Argillaceous Rocks: In these rocks, clay predominates. The rocks may be dense and compact or may be soft. Ex: slates, Laterites etc. c) Calcareous rocks: In these rocks, calcium carbonate predominates. The durability to these rocks will depend upon the constituents present in surrounding atmosphere. Ex: Lime Stone, marble etc. S No 1 2 3 4 5 6

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Rock type Igneous

Sedimentary

Building Stone Basalt Diorite Granite Syenite Limestone Sandstone

2

Crushing Strength ( N/mm ) 150 – 185 90 – 150 75 – 127 90 – 150 54 64

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7 8 9

Metamorphic

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Shale Gneiss Slate

0.20 – 0.60 206 – 370 75 - 207

USES OF STONES: 1. Structure: Stones are used for foundations, walls, columns, lintels, arches, roofs, floors, damp proof course etc. 2. Face works. Stones are adopted to give massive appearance to the structure. Walls are of bricks and facing is done in stones of desired shades. This is known as composite masonry. 3. Paving stones: These are used to cover floor of building of various types such as residential, commercial, industrial etc. They are also adopted to form paving of roads, foot paths etc. 4. Basic material: Stones are disintegrated and converted to form a basic material for cement concrete, mo rum of roads, calcareous cements, artificial stones, hallow blocks etc. 5. Misalliances: Stones are also used for (i) ballast for railways (ii) flux in blast furnace (iii) Blocks in the construction of bridges, piers, abutments, retaining walls, light houses, dams etc. QUALITIES OF A GOOD BUILDING STONE: The following are the qualities or requirements of a good building stone. 1. Crushing strength: For a good building stone, the crushing strength should be greater than l000kg per cm2 (100 N/mm2). 2. Appearance: Good building stone should be a uniform colour, and free from clay holes, spots of other colour bands etc. capable of preserving the colour for long time. 3. Durability: A good building stone should be durable. The factors like heat and cold alternative wet and dry, dissolved gases in rain, high wind velocity etc. Affect the durability. 4. Fracture: For good building stone its fracture should be sharp, even and clear. 5. Hardness: The hardness greater than 17 treated as hard used in road works. It is between 14 to 17, less than 14 is said be poor hardness. 6. Percentage wear: For a good building stone, the percentage wear should be equal to or less than 3 percent. 7. Resistance to fire: A good building stone be fire proof. Sandstone, Argillaceous stone resists fire quite well. 8. Specific gravity: For a good building stone the specific gravity should be greater than 8.7 or so. 9. Texture: A good building stone should have compact fine crystalline structure should be free from cavities, cracks or patches of stuff or loose material. 10. Water absorption: For a good building stone, the percentage absorption by weight after 24 hours should not exceed 0.60. 11. Seasoning: Stones should be well seasoned before putting into use. A period of about 6 to 12 months is considered to be sufficient for proper seasoning. 12. Toughness Index: Impact test, the value of toughness less than 13 – Not tough, between 13 and 19 – Moderate, greater than 19- high.

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ENGINEERING ASPECTS OF STONES: A building may be defined as a sound rock that can be safely used in construction. Stone masonry is an engineering art that is preserved in many historical building in all parts of the world and in developing countries where it represents affordable and cost-effective housing construction. The following are the qualities of stone which made it as an engineering material: 1. High compressive strength 2. Less absorption of water 3. Resistance to abrasion 4. Hard and tough 5. Less porosity 6. Durable 7. Economical when quarry site is nearer 8. Available in different colours and shades 9. Gives massive appearance to structure 10. Provide stable foundation to structure CHARACTERISTICS OF GOOD STONES: In selecting a stone for engineering work the following characteristics should be looked into. 1. It should be strong hard and durable to withstand the deteriorating action of rough weather. 2. It should have pleasing uniform colour and fine grained compact texture. 3. It should remain unaffected by smoke and atmospheric acids. 4. It should be free from cracks cavities, flaws, decay or patches of soft material. 5. The surface of a freshly broken stone should be sharp, clean and bright with uniformity of colour and texture. 6. The specific gravity of stone should not in any case be less than 2.7. 7. It should be crystalline and homogeneous structure. 8. It should not absorb more than 0.60percent of its weight of water after 24hours of immersion. 9. It should be seasoned. 10. It should be easily workable. 11. It should stand fire well for some time without serious injury. 12. It should be easily obtainable and economical. ADVANTAGES OF DRESSING THE STONES: The following are the advantages of dressing 1. Dressed stones call be transported easily & economically. 2. Dressed stones can be used for stone masonry works, ornamental works. 3. Dressing of stones at quarry site reduces the cost of labour (as it is possible to get cheap labour at quarry site). 4. Accumulation of wastes at the site gets reduced. RYMEC,Ballari.

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FACTORS AFFECTING THE SELECTION OF A TYPE OF DRESSING The following are the factors which affect the selection of type of dressing of stone • The architectural effects desired • The position of stone and its function in the structure • The atmospheric considerations TYPES OF DRESSING: The different types of surface dressing or surface finish of stones are discussed below: 1. Scabbling dressing The dressing in which irregular projections of the queried stone are removed by means of a scabbling hammer is called scabbling dressing. This is usually done at quarry. The stones thus dressed roughly are called scabbled stones, and the surface finish provided in this way is termed as scabbling finish. 2. Hammer dressing The dressing in which the stones are made roughly square or rectangular by means of a mason's hammer is called hammer dressing. The stone blocks are simply made square to enable the mason-to provide proper joints in the masonry work. 3. Rough tooled dressing The dressing in which projections from the surface of the stone block arc removed by means of chisels until no portion of the dressed surface is more than 10mm from a straight edge placed on it is called rough tooled dressing or one-line dressing. The stones thus dressed are called rough tooled or one line dressed stones and the surface finish provided in this way is known as rough tooled finish. This type of dressed stones generally used for coursed rubble masonry. 4. Tooled dressing The dressing in which all the projections from the surface of stone blocks are removed by means of chisels until no portion of the surface is more than 3 mm from a straight edge placed on it, is called tooled dressing. This type of dressed stones used for superior type of coursed rubble masonry.

Fig.1.Hammer and Tooled dressed surface 5. Furrowed finish The surface of the exposed face is finished by making a number of vertical and horizontal grooves about 10 mm wide. 2 cm wick margin is also made around the edges or the exposed face. 6. Reticulated finish

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In this finishing 2.cm wide margin, chamfered at 45° is marked on the edges and irregular depressions are developed on the enclosed space of the exposed face. Fig.2 Furrowed and Reticulated finish

7. Vermiculated finish This finish appears just like worm eaten surface. It is similar to reticulated finish except that depressions in this surfacing are more curved and good looking in appearance. 8. Finely punched dressing The dressing in which all the projections from the surface of a stone block are removed by means of pointed tools or a punch giving a clotted appearance is called finely punched dressing. This type of dressing is usually specified to give architectural appearance to the masonry work. Fig3. Punched and Polished surface

9. Cut stone dressing The dressing in which all the projections from all the faces or a stone block are removed by means of a sharp chisel, rend ring the surface free of chisel marks is called cut stone dressing. This type of dressed stones used for ashlar masonry. 10. Rubbed dressing The dressing in which a perfectly smooth surface finish is obtained by grinding or rubbing a cut stone by hand or by machine is called rubbed dressing. This type of dressed stone used for ashlar masonry. 11. Polished dressing The dressing in which the rubbed stone surfaces are polished by manual labour, using sand and water pumice stone etc. or by means of a rubbing machine is called polished dressing.

Deterioration of stones The stones with exposed faces are acted upon by various atmospheric and external agents so as to cause their deterioration. Following are the cause for deterioration of stones. 1) Alternative wetness and drying: The stones are made wet by various agencies such as rain, frost, dew etc. Such wet surface is dried by sunlight. It is found that stones subjected to such alternate wetness

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and drying wears out quickly. 2) Frost: In hill stations or very cold places, the moisture present in the atmosphere is deposited in the pores of stones. At freezing point, this moisture freezes and it expands in volume which causes the splitting of stone. 3) Impurities in atmosphere: The atmosphere contains various impurities which have adverse effects on stones. For instance, the acids and fumes are predominant in industrial areas. These impurities acts on carbonates of lime and causes deterioration. 4) Living organisms: Some living organisms like worms an bacteria act upon stones and deteriorate them. The organisms make holes in stones and thus weaken them. They also secrete organic acids which have a corrosive effect on stone minerals. 5) Movement of moisture: If stones of different variety such as limestone and sandstone are used side by side in the same structure, the chemicals formed by the action of atmospheric agents on one stone may move to the other and cause deterioration of both stones. 6) Nature of mortar: The nature of mortar used as a binding material in stone masonry may be such that it may react chemically with any one of the constituents of stones and thus it may lead to the disintegration of stones. 7) Rain water: The action of rain water on stones is two-fold – physical and chemical. The rain wets the surface of stone and it is dried by sunlight. Such alternate wetness and drying results in the disintegration of stones. This is the physical action of water. The rain water, as it descends through the atmosphere to the surface of earth, absorbs carbon dioxide (CO2), hydrogen sulphide (H2S) and other gases present in the atmosphere. These gases acts adversely on stones and they cause decay of stones. This is the chemical action of rain water. 8) Temperature variations: the rise of temperature results in expansion of stones. The fall of temperature causes contraction of stones. If rise and fall of temperatures are frequent, the stones are easily deteriorated because of the setting up internal stresses. 9) Vegetative growth: The creepers and certain trees develop on stone surface with their roots in joints between stones. Such roots attract moisture and keep the stone surface damp. At the same time they try to expand. Such actions accelerate the decay ofstones. 10) Wind: The wind contains fine particles of dust. If is blowing with high velocity, such particles will strike against the stone surface and thus the stones will be decayed. The wind also allows rain water to enter pores of stones with force. Such water on freezing expands and split the stones.

Preservation of stones The decay of building stones of inferior is to some extent prevented if they are properly preserved. For this purpose, the preservatives are applied on the stone surfaces. An ideal preservative has the following properties: 1. 2. 3. 4. 5. 6.

It does not allow moisture to penetrate the stone surface. It does not develop objectionable color. It hardens sufficiently in order to resist the atmospheric agents. It is easily penetrated in stone surface. It is economical It is non-corrosive and harmless. RYMEC,Ballari.

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7. It remains effective for long time after drying. 8. Its application on stone surface is easy. The choice of a preservative depends on chemical composition and location of structure. Following are the preservatives which are commonly adopted to preserve the stone: (i) Coal tar: If coal tar is applied on stone surface, it preserves stone. But the color of coal tar produces objectionable appearance and surface coated with color tar absorbs heat of the sun. Hence this preservative is not generally adopted because it spoils the color of the stone. (ii)Linseed oil: This preservative may be used either as raw linseed oil or boiled linseed oil. The raw linseed oil does not disturb the original shade of stone. But it requires frequent renewal, usually once in year. The boiled linseed oil lasts for a long period, but it makes the stone surface dark. (iii) Paint: An application of paint on stone surface serves as a preservative. The paint changes the original color of the stone. It is applied under pressure, if deep penetration is required. (iv) Paraffin: This preservative may be used alone or it may be dissolved in neptha and then applied on stone surface. It changes the original color of tone. (v) Solution of alum & soap: The alum and soft soap are taken in proportion of about 0.75N and 0.5N respectively and they are dissolved in a liter of water. This solution when applied on stone surface it acts as preservative. (vi) Solution of baryta: A solution of barium hydroxide Ba(OH)2 when applied on stone surface acts as preservative. This is used when the decay of stone is mainly due to calciumsulphate. Ba(OH)2 + CaSO4 = BaSO4 + Ca(OH)2

The barium sulphate id insoluble and it is least affected by atmospheric agents. Ca(OH)2 absorbs CO2 from atmosphere and forms CaCO3 which adds to the strength to the stones

BRICKS Bricks are obtained by moulding clay in rectangular blocks of uniform size and then by drying and burning these blocks. As bricks are of uniform size, they can be properly arranged, light in weight and hence bricks replace stones. COMPOSITION OF BRICKS: • Composition – Following are the constituents of good brick earth. • Alumina: - It is the chief constituent of every kind of clay. A good brickearth should contain 20 to 30 percent of alumina. This constituent imparts plasticity to earth so that it can be moulded. If alumina is present in excess, raw bricks shrink and warp during drying and burning. • Silica-A good brick earth should contain about 50 to 60 percent of silica. Silica exists in clay either as free or combined form. As free sand, it is mechanically mixed with clay and in combined form; it exists in chemical composition with alumina. Presence of silica prevents crackers shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks. Durability of bricks depends on the proper proportion of silica in brick earth. Excess of silica destroys the cohesion between particles and bricks become brittle.

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