Lec 1 bricks - BUILDING CONSTRUCTION MATERIALS PDF

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BUILDING CONSTRUCTION MATERIALS...

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LECTURE #01

Bricks Bricks are blocks of tampered clay molded to suitable shapes and sizes while it is still in plastic condition, dried in the sun and burnt. Classification Bricks are broadly classified Into Two Categories 1) Sun Dried Bricks Or Kacha bricks 2) Burnt bricks or Pucca bricks 1) Sun dried bricks These bricks after moulding have been dried in the sun and are used in the construction of temporary and cheap structures. These types of bricks should not be used at places of heavy rains. 2) Burnt bricks or Pucca bricks These are of the following four types a) First class bricks  These are well burnt bricks of uniform color.  These are free from cracks.  Scratch with finger nails leaves no mark  These do not absorb more than 20% of their weight of water  The crushing strength should not be less than 105kg/cm2  When struck with each other give a sharp metallic ringing sound  These are free from nodules of free lime Uses: used in face work of structures not to be plastered Used in flooring and reinforced brickwork b) Second class bricks These are as hard and well burnt bricks as the first class but may be somewhat irregular in shape or size and may have slight rough surface. The crushing strength of this brick-type should be above 70 kg/cm2. These bricks don't absorb more than 22% water of its own weight after 24 hours immersion in fresh water. These bricks may have hair cracks and their edges may not be sharp and uniform. Uses: used in unimportant situations or in places where the masonry is to be plastered. Used as brick ballast in RCC work and in lime concrete. BY Engineer Asghar Hussain Shah

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LECTURE #01 c) Third Class Bricks:  These are under burnt bricks ,  these are soft  These have lighter color  These emit a dull sound when struck against each other  It doesn't absorb more than 25% water of its own weight when immersed 24 hours in fresh water.  Crushing strength of this type is more than 35 kg/cm2?. Uses: these are used in temporary constructions not subjected to heavy loads or too heavy rains d) Over Burnt Bricks: These are over burnt bricks that are being near the fire in the kiln get fused and lose their shape Uses: Used in the foundations of structures Used as aggregate for concrete Used as road metal Nomenclature of cut bricks I. Nomenclature based on brick size Frequently, the Builder must cut the brick into various shapes. The most common shapes are shown in figure .They are called half or bat, three-quarter closure, quarter closure, king closure, queen closure, and split. They are used to fill in the spaces at corners and such other places where a full brick will not fit. The six surfaces of a brick are called the cull, the beds, the side, the end, and the face, as shown

BY Engineer Asghar Hussain Shah

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ii. Nomenclature based on climatic conditions This type of classification divides brick into grades according to the probable climatic conditions to which it is to be exposed. GRADE SW is brick designed to withstand exposure to below-freezing temperatures in a moist climate like that of the northern regions of our country. GRADE MW is brick designed to withstand exposure to below-freezing temperatures in a drier climate than that mentioned in the previous paragraph. GRADE NW is brick primarily intended for interior or backup brick. It may be used exposed, however, in a region where no frost action occurs, or in a region where frost action occurs, but the annual rainfall is less than 15 in. Standard Tests of Bricks BY Engineer Asghar Hussain Shah

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LECTURE #01 Burnt clay bricks are subjected to the following tests a) Test for compressive strength (crushing strength) b) Test for water absorption c) Test for efflorescence a) Test for compressive strength (crushing strength) The brick specimen is immersed in water for 24 hours. The frog of the brick is filled flush with 1:3 cement mortar and the specimen is stored in damp jute bag for 24 hours and then immersed in clean water for 24 hours. The specimen is placed in compression testing machine with 6 mm plywood on top and bottom of it to get uniform load on the specimen. Then load is applied axially at a uniform rate of 14 N/mm2. The crushing load is noted. Then the crushing strength is the ratio of crushing load to the area of brick loaded. Average of five specimens is taken as the crushing strength. b) Test for water absorption Brick specimens are weighed dry. Then they are immersed in water for a period of 24 hours. The specimen are taken out and wiped with cloth. The weight of each specimen in wet condition is determined. The difference in weight indicates the water absorbed. Then the percentage absorption is the ratio of water absorbed to dry weight multiplied by 100. The average of five specimens is taken. Water absorption=w2-w1/w1 *100 Where w1=weight of dry brick W2=weight of wet brick after 24 hours immersion in water c) Test for efflorescence Efflorescence is a fine, white, powdery deposit of water-soluble salts left on the surface of masonry as the water evaporates. These efflorescent salt deposits tend to appear at the worst times; usually about a month after the building is constructed, and sometimes as long as a year after completion. Place the brick specimen on its end in a glass dish containing water to a depth of 25 mm in a well-ventilated room. After all the water is absorbed or evaporated again add water for a depth of 25 mm. After second evaporation observe the bricks for white/grey patches. The observation is reported as ‘nil’, ‘slight’, ‘moderate’, ‘heavy’ or serious to mean (a) Nil: No patches BY Engineer Asghar Hussain Shah

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LECTURE #01 (b) Slight: 10% of area covered with deposits (c) Moderate: 10 to 50% area covered with deposit but unaccompanied by flaking of the surface. (d) Heavy: More than 50 percent area covered with deposits but unaccompanied by flaking of the surface. (e) Serious: Heavy deposits of salt accompanied by flaking of the surface. Qualities of Good Bricks The qualities of good bricks are as listed below: Colour Colour should be uniform and bright. Shape Bricks should have plane faces. They should have sharp and truly right angled corners. Texture Bricks should have fine, dense and uniform texture. A fractured surface should not show fissures, cavities, loose grit and unburnt lime. Size Bricks should be of standard size as prescribed by the standard code. Soundness Bricks should give a metallic sound when struck with a hammer or with another brick. Strength Crushing strength of bricks should be as high as possible. The Indian Standard code does not permit the use of any brick with crushing strength of less than 55kg/cm2. A field test for strength is that when dropped flat from a height of 0.9m to 1m on a hard ground, the brick should not break into pieces. Water absorption After immersing bricks in cold water for 24 hours, water absorption of bricks should not be more than 20 per cent by weight. Efflorescence Bricks should not show white patches when soaked in water for 24 hours and then allowed to dry in shade. White patches are due to the presence of sulphates of calcium, magnesium, sodium and potassium, and they keep the masonry permanently in a damp and wet condition. Thermal conductivity Bricks should have low thermal conductivity so that buildings built with them are cool in summer and warm in winter. Sound insulation BY Engineer Asghar Hussain Shah

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LECTURE #01 Heavier bricks are poor insulators of sound while light weight and hollow bricks provide good sound insulation. The strength and sound insulation properties of bricks contradict each other. Hence, bricks with unnecessarily too high strength (heavy bricks) need not be used. Fire resistance Fire resistance of bricks is usually good. In fact sometimes bricks are used to encase steel columns as a measure of fire protection. Defects in bricks Over burning of bricks: Bricks should be burnt at temperatures at which incipient, complete and viscous vitrification occur. However, if the bricks are over burnt, a soft molten mass is produced and the bricks lose their shape. Such bricks are not used for construction works. Under burning of bricks: When bricks are not burnt to cause complete vitrification, the clay is not softened because of insufficient heat and the pores are not closed. This results in higher degree of water absorption and less compressive strength. Such bricks are not recommended for construction works. Bloating: This defect observed as spongy swollen mass over the surface of burnt bricks is caused due to the presence of excess carbonaceous matter and sulphur in brick-clay. Black core: When brick-clay contains bituminous matter or carbon and they are not completely removed by oxidation, the brick results in black core mainly because of improper burning. Efflorescence: This defect is caused because of alkalis present in bricks. When bricks come in contact with moisture, water is absorbed and the alkalis crystallize. On drying grey or white powder patches appear on the brick surface. Chuffs: The deformation of the shape of bricks caused by the rain water falling on hot bricks is known as chuffs Spots: Iron sulphide, if present in the brick clay, results in dark surface spots on the brick surfaces. Such bricks though not harmful are unsuitable for exposed masonry work. Brick earth Composition: For the preparation of bricks, clay or other suitable earth is moulded to the desired shape after subjecting it to several processes. After drying, it should not shrink and no crack should develop. The clay used for brick making consists mainly of silica and alumina mixed in such a proportion that the clay becomes plastic when water BY Engineer Asghar Hussain Shah

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LECTURE #01 is added to it. It also consists of small proportions of lime, iron, manganese, sulphur, etc. The proportions of various ingredients are as follows: Silica 50 to 60% Alumina(clay) 20 to 30% Lime 10% Magnesia less than 1% Ferric oxide(iron oxide) less than 7% Alkalis less than 10% Functions of various ingredients of brick earth Silica: It enables the brick to retain its shape and imparts durability, prevents shrinkage and warping. Excess of silica makes the brick brittle and weak on burning. A large percentage of sand or uncombined silica in clay is undesirable. However, it is added to decrease shrinkage in burning and to increase the refractoriness of low alumina clays. Alumina: Alumina absorbs water and gives plastic property. If alumina is present in excess of the specified quantity, it produces cracks in brick on drying. Clays having exceedingly high alumina content are likely to be very refractory. Lime: lime normally constitutes less than 10 per cent of brick earth. Lime in brick clay has the following effects: 1. Reduces the shrinkage on drying. 2. Causes silica in clay to melt on burning and thus helps to bind it. 3. In carbonated form, lime lowers the fusion point. 4. Excess of lime causes the brick to melt and the brick loses its shape. 5. Red bricks are obtained on burning at considerably high temperature (more than 800°C) and buff-burning bricks are made by increasing the lime content. Magnesia: Magnesia rarely exceeding 1 per cent affects the color and makes the brick yellow, in burning; it causes the clay to soften at slower rate than in most case is lime and reduces warping. Iron oxide: Iron oxide constituting less than 7 per cent of clay, imparts the following properties: 1. Gives red color on burning when excess of oxygen is available and dark brown or even black color when oxygen available is insufficient; however, excess of ferric oxide makes the brick dark blue. 2. Improves impermeability and durability. 3. Tends to lower the fusion point of the clay, especially if present as ferrous oxide. 4. Gives strength and hardness. Different types of bricks: BY Engineer Asghar Hussain Shah

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LECTURE #01 Facing Brick Facing brick are intended for use in both structural and nonstructural masonry, including veneer, where appearance is a requirement. Hollow Brick Hollow brick are used as either building or facing brick but have a greater void area. Most hollow brick are used as facing brick in anchored veneer. Hollow brick with very large cores are used in reinforced brickwork and contain steel reinforcement and grout. Building Brick Building brick are intended for use in both structural and nonstructural brickwork where appearance is not a requirement. Building brick are typically used as a backing material. Thin Brick Thin veneer brick have normal face dimensions but a reduced thickness. They are used in adhered veneer applications. Paving Brick Paving brick are intended for use as the wearing surface on clay paving systems. As such they are subject to pedestrian and light or heavy vehicular traffic. Glazed Brick Glazed brick have a ceramic glaze finish fused to the brick body. The glaze can be applied before or after the firing of the brick body. These brick may be used as structural or facing components in masonry.

Block • A concrete block is primarily used as a building material in the construction of walls. • A concrete block is one of several precast concrete products used in construction • Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design. • A concrete block is primarily used as a building material in the construction of walls. • A concrete block is one of several precast concrete products used in construction • Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design.

BY Engineer Asghar Hussain Shah

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LECTURE #01 In addition to the basic components, the concrete mixture used to make blocks may also contain various chemicals, called admixtures, to alter curing time, increase compressive strength, or improve workability. Types of concrete block • Dense aggregate blocks (heavyweight) – suitable for load-bearing external walls. • Lightweight aggregate blocks – internal load-bearing walls and non-loadbearing partitions (Lightweight concrete blocks are made by replacing the sand and gravel with expanded clay, shale, or slate.) Blocks size • The shapes and sizes of most common concrete blocks have been standardized to ensure uniform building construction. • 8-by-8-by-16 block, with the nominal measurements of 8 in (20.3 cm) high by 8 in (20.3 cm) deep by 16 in (40.6 cm) wide. This nominal measurement includes room for a bead of mortar, and the block itself actually measures 7.63 in (19.4 cm) high by 7.63 in (19.4 cm) deep by 15.63 in (38.8 cm) wide. •

BY Engineer Asghar Hussain Shah

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LECTURE #01

Standard types of blocks • Stretcher. A stretcher block is the most commonly used block in construction. It is laid with its • Corner. A corner block is used for corners at simple window and door openings. • Double Corner or Pier. A double-corner or pier block is used for constructing piers pilasters or for any other purpose where both ends of the block would be visible. • Bull Nose. A bull-nose block serves the same purpose as a corner block, but it is used where round corners are desired. • Jamb. A wood-sash jamb block is used with a stretcher and a corner block around elaborate window openings. The recess in the block allows room for the various casing members, as in a double hung window. • Most Common Block. The most common concrete block is the hollow, load-bearing stretcher block, which is 8 by 8 by 16 inches nominal size, but 7 5/8 by 7 5/8 by 15 5/8 inches actual size. The heavyweight load-bearing stretcher block weighs from 40 to 50 pounds. Tiles: Tiles are thin slabs used for covering roofs, for flooring or for making drains and may be formed of a) Brick earth burnt in kilns and b) concrete BY Engineer Asghar Hussain Shah

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LECTURE #01 Brick earth used for manufacturing tile is more pure and is prepared more thoroughly than the one used for manufacturing bricks. Tiles, being thinner require careful burning. Manufacturing of tiles: Various operations involved in the manufacture of tiles are: i) Preparation of clay ii) moulding iii) drying and iv) burning i) Preparation of clay: Clay to be used for manufacturing tiles needs to be prepared more intimately. The clay should have no pebbles or grit. For ordinary tiles the clay may be ground finely in the crushing mill and then intimately mixed in a pug mill. For superior tiles the clay is finely ground and then mixed with sufficient quantity of water in a tank. The solution is then allowed to stand quietly in the tank resulting in the sittling of heavy coarse particles. Water containing fine clay in solution is drained off to other tanks where it is allowed to dry leaving the clay ready for moulding. ii) Moulding: three common methods for moulding are: Moulding by wooden patterns: tiles that do not have a uniform section throughout their length are moulded on wooden patterns. The tile is first moulded flat and when it has become a little dry then it is pressed round a wooden pattern to give the desired shape. Moulding on a potter’s wheel: tiles having perfectly circular shapes are conveniently moulded on a plotter’s wheel. Tiles with diameters varying with their lengths can also be very conveniently moulded on the potter’s wheel. Moulding by mechanical means: this method is applicable when the tile to be moulded has a uniform section throughout their lengths. In it the prepared clay is forced under pressure through an opening having the same cross-section as that of tile. The tile is then cut to the desired length with a fine wire. iii) Drying: Great care has to be exercised in the drying of tiles. In the initial stages these should not be subjected to the action of direct sun or strong winds otherwise because of resulting quick drying the tiles are likely to crack and warp. These should be dried in the shade. iv) Burning: the burning should be done carefully so as to avoid cracking and warping. The burning has to be done gradually and if the tiles are being burnt in the same kiln then the upper part of kilns, where the heat is less, is reserved for tiles as those are thinner and require lesser heat. Ceramic tiles: Solid concrete block is also becoming popular, especially in the northern part of KPK or Azad Kashmir because of the unavailability of brick kiln and high cost of brick imported from other part of the country. The blocks are manufactured in BY Engineer Asghar Hussain Shah

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LECTURE #01 small factories in semi-automatic machines. The different sizes of blocks produced are 12 x 8 x 6 inch (30.5 x 20.3 x 15.2 mm), 12 x 8 x 5 inch (30.5 x 20.3 x 12.7 mm) and 12x 8 x 4 inch (30.5 x 20.3 x 10.1 mm) (length x width x thickness). Earthquake Reconstruction and Rehabilitation Agency (ERRA) construction guideline-2006 recommends 12 x 8 x 6 inch (30.5 x 20.3 x 15.2 mm) concrete block for the construction of building.

BY Engineer Asghar Hussain Shah

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