Building Material Bricks Lec

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BRICKS
Civil Engineering Materials
Fall Semester 2014
Department of Civil Engineering
Iqra National University Peshawar
Civil Engineering Materials

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Building Materials
• Building stones
• Bricks and clay products
• Cement concrete
• Timber and wood products
• Metals and alloys
• Paints, varnishes, distempers
• Asphalt, bitumen and tar
• Plastics and fibers
• Glass
• Asbestos, adhesives and abrasives

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Bricks and Clay Products

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Clay Products
• 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 more strong, hard and durable

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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, and porcelain

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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

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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

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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

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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

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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

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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

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Classification of Bricks
Bricks
Sun Dried
Katcha
Un Burnt
Burnt
Pucca
Practice Usage Finish Manufacture Burning Strength

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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

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Classification of Burnt Bricks
Burnt
Bricks
Practice Usage Finish Manufacture
1st Class
2nd Class
3rd Class
4th Class
Common
Brick
Facing
Brick
Engg
Brick
Sand
Faced
Rustic
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

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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/mm2
– Recommended for pointing, exposed face work, flooring and
reinforced brick work

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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/mm2
– 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

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Classification of Burnt Bricks
Strength Based
• Classes
– 350 (35 N/mm2) 125 (12.5 N/mm2)
– 300 (30 N/mm2) 100 (10 N/mm2)
– 250 (25 N/mm2) 75 (7.5 N/mm2)
– 200 (20 N/mm2) 50 (5 N/mm2)
– 175 (17.5 N/mm2) 25 (2.5 N/mm2)
– 150 (15 N/mm2)
• Sub Classes
– Subclass A. Tolerance 0.3% in dimensions
– Subclass B. Tolerance 0.8% in dimensions
• Heavy Duty. Compressive strength > 40 N/mm2

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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

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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

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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

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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
Al2O3. 2H2O called kaolin.
• Alumina or clay 20-30% by weight
• Silica or sand 35-50% by weight
• Silt 20-35% by weight
• Remaining ingredients 1-2% by weight
– Lime (CaO)
– Magnesia (MgO)
– Iron oxides
– Alkalis (Sodium potash, etc)
• Water

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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.

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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

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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

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Operations in Manufacturing of Bricks
• Preparation of Brick Earth
– Un-soiling
– Digging
– Weathering
– Blending
– Tempering
• Molding of Bricks
• Drying of Bricks
• Burning of Bricks

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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

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Pug Mill

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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

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Brick Molds

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Table Molding

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Plastic Molding

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Strikes

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Extruded – Wire Cut Extruded – Smooth
Wood Mold
Extruded – Raked

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Method
of Drying
Bricks

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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

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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

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Clamp or
Pazawah

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Intermittent
Kiln

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Hoffman’s
Continuous
Kiln

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Bull’s Trench Kiln

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Bull’s
Trench
Kiln

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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 scratchable by
finger nail. Produce metallic ringing sound
• Water absorption – should not exceed 20% wt
• Crushing strength – not less than 10.5 N/mm2
• Brick earth – free from stones, organic matter

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Special
Forms
of
Bricks
a. Round ended
brick
b. Cant brick
c. Splay brick
d. Cornice brick
e. Compass brick
f. Bull nosed brick
g. Perforated brick
h. Hollow brick
i. Coping brick
j. Plinth level brick
k. Split brick (Queen
closer)
l. Split brick (King
closer)

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Specially Shaped Bricks

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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.

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Testing of Bricks
• Absorption Test.
– 24 hours immersion cold water test.
• Dry bricks oven dried at 105° ± 5° C
• Room temperature cooled bricks weighed W1
• Bricks immersed in water at 27° ± 2° C for 24 hrs
• Soaked bricks weighed W2
• Water absorption in % = (W2 – W1)/W1 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 % = (W3 – W1)/W1 x 100

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Testing of Bricks
• 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
– Nil imperceptible efflorescence
– Slight deposit covers area < 10% of exposed
area
– Moderate deposit covers exposed area 10% to
50%
– Heavy deposit covers exposed area > 50%
– Serious deposits are heavy and powder
or flake away the surface

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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 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

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Brick Masonry
• Brick sides
– Header
– Stretcher
• Brick Bonds
– English
• Brick Masonry Patterns
– Herringbone
– Basket weave
– Flemish

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Basic Brickwork Terminology
Bed
Joint
Head
Joint
Course - horizontal layer of brick

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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

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Joint Color that “Blends” w/ Brick Color

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Concave Joints

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Raked Joints

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Simulated Precast Concrete Lintel
(actually a steel lintel supports the assembly)

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Arch

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