5/1/2015 6:01 PM CE-115 Civil Engineering Materials3 Comparison of Stones and Bricks Stone –Natural material –Heavier –High dressing cost –Costly except in hilly areas –Less porous, good for hydraulic structures –Greater strength –Better heat conductor –Weather resistant –Superior quality stone is monumental and decorative Bricks –Manufactured from clay –Lighter –Moldable to any shape –Cheaper except in hilly areas –More porous, needs water proof treatment –Reasonable for normal loads –Poor heat conductor –Needs pointing and plastering –Architectural effect is achievable
5/1/2015 6:01 PM CE-115 Civil Engineering Materials5 Clay Products –Bricks –Tiles –Fire clays and fire bricks –Terracotta –Earthenware –Clay pipes Bricks –Block of tampered clay or ceramic material molded to desired shape and size, sun dried and if required burnt to make it strong, hard and durable
5/1/2015 6:01 PM CE-115 Civil Engineering Materials6 Bricks Commonly it is rectangular in shape –Length = twice width of brick + thickness of mortar –Height = multiple of width of brick –Usual size available in Pakistan is 8¾ x 4¼ x 2 ¾ inches to make it 9 x 4.5 x 3 inches with mortar –Indian Standard size 19 x 9 x 9 cm and 19 x 9 x 4 cm to make it 20 x 10 x 10 cm and 20 x 10 x 5 cm with mortar Bricks are most common form of structural clay products; others being tiles, pipes, terracotta, earthenware, stoneware, porcelain, and majolica
5/1/2015 6:01 PM CE-115 Civil Engineering Materials7 Historical Development Began as low walls of stones or caked mud Sun-dried bricks - With the availability of fire became burnt bricks Invention of kilns made mass production of bricks easy Limestone turned into lime mortar replaced mud as mortar In Mesopotamia, palaces and temples were built of stone and sun-dried bricks in 4000 B.C. The Egyptians erected their temples and pyramids of stones by 3000 B.C. By 300 B.C., Greeks perfected their temples of limestone and marble Romans made the first large-scale use of masonry arches and roof vaults in their basilica, baths and aqueducts
5/1/2015 6:01 PM CE-115 Civil Engineering Materials8 Historical Development Medieval and Islamic civilizations perfected masonry vaulting to a high degree of development - Islamic craftsmen built palaces, markets, and mosques of bricks and often faced them with brightly glazed tiles Europeans built fortresses and cathedrals using pointed vaults and flying buttresses In America and Asia other cultures were building with stones During industrial revolution, machines were developed to quarry and cut stones, mould bricks, and speed the transportation of these materials to site of building Portland cement came into wide use and this enabled the construction of masonry building of greater strength and durability
5/1/2015 6:01 PM CE-115 Civil Engineering Materials9 Historical Development Late in 19th century tall buildings were built, of steel and reinforced concrete (pored into simple forms), economically Development of hollow concrete forms in 19th century averted the extinction of masonry as a building material - Cavity wall, developed by the British during the earlier part of the 19th century also contributed to the survival of masonry as a building material This facilitated the introduction of thermal insulation High strength mortars, high-strength masonry units, and complex shapes of masonry units extended the use of masonry for buildings
5/1/2015 6:01 PM CE-115 Civil Engineering Materials10 Historical Development Through the mid-1800s –Primary Building Materials Late 1800s –New Products Developed –Ended Masonry’s Dominance 20th Century Developments –Steel Reinforced Masonry –High Strength Mortars –High Strength Masonry Units –Variety of Sizes, Colors, Textures & Coatings
5/1/2015 6:01 PM CE-115 Civil Engineering Materials11 Adobe Spanish-American name applied to sun-dried brick and to the clay soil from which the brick is made Adobe soil is composed of very fine mixture of clay, quartz, and other minerals Adobe soil has great plasticity when moist, but when dry is so coherent that tillage is almost impossible Soil is used combined with straw, molded and baked in sun for 7 to 14 days Used in regions of low rainfall and dampness
5/1/2015 6:01 PM CE-115 Civil Engineering Materials12 Civil Engineering Uses Construction of exterior and interior walls, partitions and boundary walls Construction of piers, abutments Construction of footings Construction of miscellaneous load bearing structures
5/1/2015 6:01 PM CE-115 Civil Engineering Materials13 Classification of Bricks Bricks Sun Dried Katcha Un Burnt Burnt Pucca PracticeUsageFinishManufactureBurningStrength
5/1/2015 6:01 PM CE-115 Civil Engineering Materials14 Classification of Bricks Sun Dried, Un-burnt or Kacha Bricks –After molding dried in sun, and are used in the construction of temporary structures which are not exposed to rains. Burnt or Pucca Bricks –Burnt in an oven called kiln to provide strength and durability
5/1/2015 6:01 PM CE-115 Civil Engineering Materials15 Classification of Burnt Bricks Burnt Bricks Practice 1 st Class 2 nd Class 3 rd Class 4 th Class Usage Common Brick Facing Brick Engg Brick Finish Sand Faced Rustic Manufacture Hand Made Machine Made Burning Pale Bricks Under Burnt Body Bricks Well Burnt Arch Bricks Over Burnt Strength Class A Class B Classes 350 to 35
5/1/2015 6:01 PM CE-115 Civil Engineering Materials16 Classification of Burnt Bricks Field Practice First Class Bricks –Thoroughly burnt, deep red, cherry or copper color –Straight edges, square corners, smooth surface –Free from flaws, cracks, stones and nodules –Uniform texture & ringing sound –No scratch marks with fingernails –Water absorption 12-15% of dry weight in 24 hours –May have only slight efflorescence –Crushing strength not less than 10.5 N/mm 2 –Recommended for pointing, exposed face work, flooring and reinforced brick work
5/1/2015 6:01 PM CE-115 Civil Engineering Materials17 Classification of Burnt Bricks Field Practice Second Class Bricks –Small cracks and distortions permitted –Water absorption 16-20% of dry weight allowed –Crushing strength not less than 7.0 N/mm 2 –Recommended for all hidden work and centering of RBC Third Class Bricks, Pilla Bricks –Under burnt, Soft and light colored producing dull sound –Water absorption 25% of dry weight –Recommended for temporary structures Fourth Class Bricks, Jhama, Khingar –Over burnt and badly distorted in shape and size –Brittle in nature –Ballast of these bricks used for foundation and floors and as road metal
5/1/2015 6:01 PM CE-115 Civil Engineering Materials19 Classification of Burnt Bricks Basis of Usage –Common Brick. General multi-purpose –Facing Brick. Good appearance, color, textured, durable under severe exposure –Engineering Bricks. Strong, impermeable, smooth and hard Basis of Finish –Sand Faced Brick. Textured surface by sprinkling sand inside mold –Rustic. Mechanically textured finish
5/1/2015 6:01 PM CE-115 Civil Engineering Materials20 Classification of Burnt Bricks Basis of manufacturing method –Hand Made. Hand molded –Machine Made. Wire cut, pressed and molded bricks Basis of Burning –Pale Bricks are under burnt –Body Bricks are well burnt in central portion of kiln –Arch Bricks are over burnt. Also called clinker
5/1/2015 6:01 PM CE-115 Civil Engineering Materials21 Comparison of Stones and Bricks Stone –Natural material –Heavier –High dressing cost –Costly except in hilly areas –Less porous, good for hydraulic structures –Greater strength –Better heat conductor –Weather resistant –Superior quality stone is monumental and decorative Bricks –Manufactured from clay –Lighter –Moldable to any shape –Cheaper except in hilly areas –More porous, needs water proof treatment –Reasonable for normal loads –Poor heat conductor –Needs pointing and plastering –Architectural effect is achievable
5/1/2015 6:01 PM CE-115 Civil Engineering Materials22 Ingredients of Good Brick Earth Brick earth is formed by the disintegration of igneous rocks. Potash feldspars, orthoclase or microcline yield clay minerals which decompose to yield kaolinite, a silicate of alumina. On hydration it gives a clay deposit Al 2 O 3. 2H 2 O called kaolin. Alumina or clay20-30% by weight Silica or sand35-50% by weight Silt20-35% by weight Remaining ingredients 1-2% by weight –Lime (CaO) –Magnesia (MgO) –Iron oxides –Alkalis (Sodium potash, etc) Water
5/1/2015 6:01 PM CE-115 Civil Engineering Materials23 Ingredients of Good Brick Earth Silica, Sand – Present as free sand or silicate. Its presence in clay produces hardness, resistance to heat, durability and prevents shrinkage and warping. Alumina – Fine grained mineral compound. Moldable plastic when wet, becomes hard, shrinks, warps and cracks when dry. Lime – Acts as binder for brick particles. Reduces shrinkage when present in small amount, excess causes the brick to melt and lose shape.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials24 Ingredients of Good Brick Earth Magnesia – Provides darker yellow color with iron. Usually less than 1%. Iron Oxide – Helps fusion of brick and provides light yellow to red color to brick. Should not be present as iron pyrites
5/1/2015 6:01 PM CE-115 Civil Engineering Materials25 Ingredients of Good Brick Earth Harmful Substances –Lime in excess or in lumps and pebbles, gravel, etc –Iron Pyrites –Alkalis in excess –Organic Matter –Carbonaceous Materials Additives –Fly Ash – silicates help in strength development –Sandy Loam – controls drying of plastic soil –Rice Husk Ash – controls excessive shrinkage –Basalt Stone Dust – modifies shaping, drying & firing
5/1/2015 6:01 PM CE-115 Civil Engineering Materials26 Operations in Manufacturing of Bricks Preparation of Brick Earth –Un-soiling –Digging –Weathering –Blending –Tempering Molding of Bricks Drying of Bricks Burning of Bricks
5/1/2015 6:01 PM CE-115 Civil Engineering Materials27 Preparation of Brick Earth Un-soiling – Removal of top 20 cm organic matter and freeing from gravel, coarse sand, lime etc Digging – additives spread, soil excavated, puddled, watered and left over for weathering Weathering – heaps left for one month for oxidation and washing away of excessive salts in rain Blending – sandy earth and calcareous earth mixed in right proportions with right amount of water Tempering – kneading of blended soil with feet or with a pug mill to improve plasticity and homogeneity
5/1/2015 6:01 PM CE-115 Civil Engineering Materials29 Manufacturing of Burnt Bricks Molding – giving right shape –Hand molding Ground molding. Molded on sand. No frog in bricks Table molding. Molded on stock boards with frog –Machine molding Plastic method or Stiff-Mud process. Molded stiff clay bar cut by wire into brick size pieces. Structural clay products Dry Press method. Moist powdered clay fed into machine to be molded into bricks. Roof, floor and wall tiles Drying – Removing 7-30% moisture present during molding stage. This controls shrinkage, fuel and burning time. Natural open air driers in shades
5/1/2015 6:01 PM CE-115 Civil Engineering Materials36 Manufacturing of Burnt Bricks Burning Stages –Dehydration (400-650 °C). Water smoking stage in which water from pores driven off –Oxidation (650-900 °C). Carbon eliminated and ferrous iron oxidized to ferric form. Sulphur is removed –Vitrification (900-1250 °C). Mass converted into glass like substance Incipient vitrification. Clay just softens to adherence Complete vitrification. Maximum shrinkage Viscous vitrification. Soft molten mass, loss in shape, glossy structure on cooling
5/1/2015 6:01 PM CE-115 Civil Engineering Materials37 Manufacturing of Burnt Bricks Clamp or Pazawah Burning –Alternate layers of bricks and fuel encased in mud plaster. –Fuel consists of grass, cow dung, litter, wood, coal dust –Brick layer consists of four to five courses of brick –25,000 to 100,000 bricks in three months cycle Kiln Burning –Intermittent kiln. Loaded, fired, cooled and unloaded before next loading –Continuous kiln. Bricks are loaded, fired, dried and cooled simultaneously in different chambers. Example: Bull’s trench kiln and Hoffman’s kiln
5/1/2015 6:01 PM CE-115 Civil Engineering Materials43 Characteristics of Good Bricks Size and shape – uniform size, rectangular surfaces, parallel sides, sharp straight edges Color – uniform deep red or cherry Texture and compactness – uniform texture, fractured surface should not show fissures, holes, grits or lumps of lime Hardness and soundness – not scratch able by finger nail. Produce metallic ringing sound Water absorption – should not exceed 20% wt Crushing strength – not less than 10.5 N/mm 2 Brick earth – free from stones, organic matter
5/1/2015 6:01 PM CE-115 Civil Engineering Materials48 Testing of Bricks Dimension Test. Sample size 50. 20 pieces selected to determine length, width and height tolerances. Compressive strength Test. Sample prepared from smooth, parallel face, brick is soaked 24 hours and stored under damp jute bags for 24 hours followed by further immersion in water for three days. Load applied @ 14 N/mm per minute till failure. Maximum load at failure divided by average area of bed face gives compressive strength.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials49 Testing of Bricks Absorption Test. –24 hours immersion cold water test. Dry bricks oven dried at 105° ± 5° C Room temperature cooled bricks weighed W 1 Bricks immersed in water at 27° ± 2° C for 24 hrs Soaked bricks weighed W 2 Water absorption in % = (W 2 – W 1 )/W 1 x 100 –Five hours boiling water test Oven dried bricks weight W1 Bricks immersed in water and boiled for 5 hours and then cooled down at room temperature in 16-19 hours Cooled down weight as W3 Water absorption in % = (W 3 – W 1 )/W 1 x 100
5/1/2015 6:01 PM CE-115 Civil Engineering Materials50 Testing of Bricks Warping Test. 10 bricks sample is used. –Concave warping –Convex warping Efflorescence Test. Ends of brick kept in 150 mm dia porcelain/glass dish containing 25 mm deep water at 20°–30°C till all water is absorbed –Nilimperceptible efflorescence –Slightdeposit covers area < 10% of exposed area –Moderatedeposit covers exposed area 10% to 50% –Heavydeposit covers exposed area > 50% –Seriousdeposits are heavy and powder or flake away the surface
5/1/2015 6:01 PM CE-115 Civil Engineering Materials51 Defects of Bricks Over-burning. Burnt beyond complete vitrification Under-burning. Burnt less not to cause complete vitrification Bloating. Spongy swollen mass over the surface due to excess carbonaceous matter and sulphur Black Core. Due to bituminous matter or carbon Efflorescence. Grey of white crystallization of alkalis on the surface, due to water absorption Chuffs. Deformation due to rainwater falling or hot bricks Checks or Cracks. Due to lumps of lime getting in contact with water Spots. Dark sulphur spots due to iron sulphides Blisters. Broken blisters due to air entrapped during molding Laminations. Thin lamina produced due to air entrapped in voids of clay
5/1/2015 6:01 PM CE-115 Civil Engineering Materials52 Miscellaneous Clay Products Terracotta. Ornamental, impervious, hard clay –Porous terracotta. Clay plus sawdust or cork –Polished terracotta. Glazed architectural clay Porcelain. High grade, white, zero water absorption and glazed material of clay, kaolin, quartz and feldspar –Soft porcelain –Hard porcelain Stoneware. Colored porcelain with silica and alumina. Flooring tiles Earthenware. Drain pipes, lavatory fittings, light partition walls Majolica. Italian earthenware coated with opaque white enamel, ornamented with metallic colors Glazing –Transparent glazing. Sodium chloride used while burning –Lead glazing. Burned items dipped in lead oxide solution –Opaque glazing. Borax, kaolin, chalk, color, feldspar and lead oxide fired. Resulting molten glass poured in water to give shattered look
5/1/2015 6:01 PM CE-115 Civil Engineering Materials55 Basic Brickwork Terminology Bed Joint Head Joint Course - horizontal layer of brick
5/1/2015 6:01 PM CE-115 Civil Engineering Materials56 Basic Brickwork Terminology Header - Bonds two wythes together Wythe: vertical layer 1 unit thick Soldier - Laid on its end, face parallel Rowlock - laid on face, end visible Stretcher - long dimension horizontal & face parallel to the wall
5/1/2015 6:01 PM CE-115 Civil Engineering Materials57 Joint Color that “Blends” w/ Brick Color
5/1/2015 6:01 PM CE-115 Civil Engineering Materials66 BRICK’S BONDING Stretcher Bond English Bond Flemish Bond Raking Bond English Garden Wall Bond Common / American Bond Flemish Garden Wall Bond Running Bond Herringbone Bond
5/1/2015 6:01 PM CE-115 Civil Engineering Materials67 Flemish Bond Alternate bricks are placed as header and stretcher in every course. Each header is placed centrally between the stretcher immediately above and below. This is not as strong as the English bond at 1 brick thick. Can be successfully applied in cavity wall.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials68 English Bond Alternative courses of headers and stretchers; one header placed centrally above each stretcher. This is a very strong bond when the wall is 1 brick thick (or thicker). One of the strongest brickwork bond patterns.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials69 Stretcher Bond Easiest bond to lay & minimizes the amount of cutting required Originally used for single brick walls, now called 1/2 brick walls it became the obvious choice for cavity walls as less cutting was required.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials70 Raking Bond Herringbone and diagonal bonds can be effective within an exposed framed construction, or contained within restraining brick courses.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials71 English Garden Wall Bond An alternative version of English bond with header courses being inserted at every fourth or sixth course. This is a correspondingly weaker bond. Suitable for free standing wall.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials72 English Garden Wall Bond An alternative version of English bond with header courses being inserted at every fourth or sixth course. This is a correspondingly weaker bond. Suitable for free standing wall.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials73 Common / American Bond A brickwork pattern in which all rows are stretchers, except an eighth row of headers
5/1/2015 6:01 PM CE-115 Civil Engineering Materials74 Flemish Garden Wall Bond In this variant of Flemish bond, one header is placed at every third stretcher
5/1/2015 6:01 PM CE-115 Civil Engineering Materials75 Running Bond Consist of all stretchers No header used in this bond so metal ties are used Cavity wall construction & veneered walls of brick
5/1/2015 6:01 PM CE-115 Civil Engineering Materials76 Herringbone Bond It is a purely decorative bond. It is used in floor and wall panels.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials77 CAVITY WALL “A wall constructed in 2 leaves / skins with a space / cavity between them” “A type of building wall construction consisting of an outer wall fastened to inner wall separated by an air space” FUNCTION To prevent the penetration of rain to the internal surface of the wall
5/1/2015 6:01 PM CE-115 Civil Engineering Materials79 WALL FAILURE Vertical bowing and horizontal bending or collapse of wall is usually caused by the wall not resisting vertical pressures from foundation or upper floors & roofs or horizontal pressures from strong winds and retained earth.
5/1/2015 6:01 PM CE-115 Civil Engineering Materials80 Usual cause for failure of wall are as follows: - Overloading the wall, deflection of beam above the wall will effect the wall below. - Foundation failure - Earthquake - Timber pest damage weakened the timber wall - Poor workmanship (improper brickwork)