The Time Value of Money

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(No Transcript)
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CONSTRUCTION MATERIALS and CONCRETE
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CONCRETE

• WHAT IS CONCRETE?
• Construction material
• Mixture of portland cement, water, aggregates,
• and in some cases, admixtures.
• The cement and water form a paste that hardens
• and bonds the aggregates together.
• Often looked upon as man made rock.
• Versatile construction material, adaptable to a
  wide variety of agricultural and residential
  uses.
• Strong, durable, versatile, and economical.

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01A0-4D58-AE7D-6F9FD7DE0FF7/0/ConcreteRecycler3.jp
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CONCRETE

• Can be placed or molded into virtually any shape
  and reproduce any surface texture.
• The most widely used construction material in the
  world.
• In the United States almost twice as much
  concrete is used as all other construction
  materials combined.
• The ready-mix concrete producer has made concrete
  an appropriate construction material for many
  applications.

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Composition of concrete

• Water
• Aggregates
• Chemical admixtures
• Cement

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_Concrete_Cracked_by_ivelt_resources.jpg
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WATER

• Good water is essential for quality concrete.
• Should be good enough to drink--free of trash,
  organic matter and excessive chemicals and/or
  minerals.
• The strength and other properties of concrete
  are highly dependent on the amount of water and
  the water-cement ratio.

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AGGREGATES

• Aggregates occupy 60 to 80 percent of the
• volume of concrete.
• Sand, gravel and crushed stone are the
• primary aggregates used.
• All aggregates must be essentially free
• of silt and/or organic matter.

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regate-driveway.jpg
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CHEMICAL ADMIXTURES

• Materials in the form of powder or fluids that
  are added to the concrete to give it certain
  characteristics not obtainable with plain
  concrete mixes.
• In normal use, admixture dosages
• are less than 5 by mass of cement,
• and are added to the concrete at the
• time of batching/mixing.

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CHEMICAL ADMIXTURES

• The most common types of admixtures are
• Accelerators
• - Speed up the hydration (hardening) of the
  concrete. - Typical materials used are CaCl2
  and NaCl.
• Acrylic retarders
• -Slow the hydration of concrete, and are used
  in large or difficult pours.
• - Typical retarder is table sugar, or sucrose
  (C12H22O11).

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CHEMICAL ADMIXTURES

• Air Entraining agents
• -The most commonly used admixtures for
  agricultural concrete.
• -Produce microscopic air bubbles throughout the
  concrete.
• -Entrained air bubbles
• Improve the durability of concrete exposed to
  moisture and freeze/thaw action.
• Improve resistance to scaling from deicers and
  corrosive agents such as manure or silage.

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CHEMICAL ADMIXTURES

• Water-reducing admixtures
• -Increase the workability of plastic or "fresh"
  concrete, allowing it be placed more easily, with
  less consolidating effort.
• -High-range water-reducing admixtures
  are a class of water-reducing admixtures
• Increase workability
• Reduce the water content of a concrete.
• Improves its strength and durability
  characteristics.

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REINFORCEMENT

• Strong in compression, as the aggregate
  efficiently carries the compression load.
• Weak in tension as the cement holding the
  aggregate in place can crack, allowing the
  structure to fail.
• Reinforced concrete solves these problems by
  adding either metal reinforcing bars, steel
  fibers,
• glass fiber, or plastic fiber to carry
  tensile loads.

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CEMENT

• Crystalline compound of calcium silicates and
  other calcium compounds having hydraulic
  properties.
• Considered hydraulic because of their ability to
  set and harden under or with excess water through
  the hydration of the cements chemical compounds
  or minerals

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ent_42_5_N_R.jpg
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CEMENT

• Uses
• Main use is in the fabrication of concrete
  and mortars
• Modern uses
• -Building (floors, beams, columns, roofing,
  piles, bricks, mortar, panels, plaster)
• -Transport (roads, pathways, crossings,
  bridges, viaducts, tunnels, parking, etc.)
• -Water (pipes, drains, canals, dams, tanks,
  pools, etc.)
• -Civil (piers, docks, retaining walls, silos,
  warehousing, poles, pylons, fencing)
• -Agriculture (buildings, processing, housing,
  irrigation)

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CEMENT

• HYDRAULIC CEMENTS
• Hydraulic lime Only used in specialized mortars.
  Made from calcination of clay-rich limestones.
• Natural cements Misleadingly called Roman. It is
  made from argillaceous limestones or interbedded
  limestone and clay or shale, with few raw
  materials. Because they were found to be inferior
  to portland, most plants switched.
• Portland cement Artificial cement. Made by the
  mixing clinker with gypsum in a 955 ratio.

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CEMENT

• Portland-limestone cements Large amounts (6 to
  35) of ground limestone have been added as a
  filler to a portland cement base.
• Blended cements Mix of portland cement with one
  or more SCM (supplementary cemetitious materials)
  like pozzolanic additives.
• Pozzolan-lime cements Original Roman cements.
  Only a small quantity is manufactured in the U.S.
  Mix of pozzolans with lime.

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CEMENT

• Masonry cements Portland cement where other
  materials have been added primarily to impart
  plasticity.
• Aluminous cements Limestones and bauxite are the
  main raw materials. Used for refractory
  applications (such as cementing furnace bricks)
  and certain applications where rapid hardening is
  required. It is more expensive than portland.
  There is only one producing facility in the U.S.

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PORTLAND CEMENT

• Most active component of concrete
• The greatest unit cost in concrete,
• Its selection and proper use are important in
  obtaining most economically the balance of
  properties desired for any particular concrete
  mixture.

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PORTLAND CEMENT

• The production process for portland cement first
  involves grinding limestone or chalk and alumina
  and silica from shale or clay.
• Type I/II portland cements are the most popular
  cements used by concrete producers
• -Type I cement is the general purpose cement
  and most common type. Unless an alternative is
  specified, Type I is usually used.
• -Type II cement releases less heat during
  hardening. It is more suitable for projects
  involving large masses of concrete--heavy
  retaining walls

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Types of Portland cement
Cement type Use
I1 General purpose cement, when there are no extenuating conditions
II Aids in providing moderate resistance to sulfate attack
III When high-early strength is required
IV When a low heat of hydration is desired (in massive structures)
V When high sulfate resistance is required
IA A type I cement containing an integral air-entraining agent
IIA A type II cement containing an integral air-entraining agent
IIIA A type III cement containing an integral air-entraining agent
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PORTLAND CEMENT

• Physical Properties of Portland Cements
• Fineness,
• Soundness
• Consistency
• Setting time
• Compressive strength
• Heat of hydration
• Loss of ignition

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Concrete production

• This process develops physical and chemical
  properties like mechanical strength, low moisture
  permeability, and chemical and volumetric
  stability.
• A properly proportioned concrete mix will
  provide
• Mixing concrete
• Workability
• Curing

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Mixing concrete

• Essential for
• The production of uniform concrete,
• High quality concrete.
• Equipment and methods should be capable
• of effectively mixing

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ts-HZS50.jpg
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Workability

• The ease with which freshly mixed concrete can be
  placed and finished without segregation.
• Difficult to measure but ready-mix companies
  usually have experience in determining the proper
  mix.
• Important to accurately describe what the
  concrete is to be used for, and how it will be
  placed.

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Curing

• Concrete that has been specified, batched,
  mixed, placed, and finished "letter-perfect" can
  still be a failure if improperly or inadequately
  cured.
• Usually the last step in a concrete
• project and, unfortunately,
• is often neglected even by professionals.
• 
  
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Curing

• Curing has a major influence on the properties of
  hardened concrete such as durability, strength,
  water-tightness, wear resistance, volume
  stability, and resistance to freezing and
  thawing.
• Proper concrete curing for agricultural and
  residential applications involves keeping newly
  placed concrete moist and avoiding temperature
  extremes (above 90F or below 50F) for at least
  three days.
• A seven-day (or longer) curing time is
  recommended.

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Curing

• The best curing method depends on
• Cost,
• Application equipment required,
• Materials available,
• Size and shape of the concrete surface.
• Prevent the loss of the mixing water from
  concrete by sealing the surface.
• Can be done by
• Covering the concrete with impervious paper or
  plastic sheets,
• Applying membrane-forming curing compounds.

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Curing

• Begin the curing as soon as the concrete has
  hardened sufficiently to avoid erosion or other
  damage to the freshly finished surface.
• Usually within one to two hours after placement
  and finishing.

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Properties of concrete

• Strength
• Elasticity
• Cracking
• Shrinkage cracking
• Tension cracking

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Strength

• Concrete has relatively
• High compressive strength,
• Low tensile strength
• Fair to assume that a concrete sample's tensile
  strength is about 10-15 of its compressive
  strength
• The ultimate strength of concrete is influenced
  by
• - water-cementitious ratio
• -the design constituents
• - the mixing
• -placement
• -curing methods

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Elasticity

• Function of the modulus of elasticity of the
  aggregates and the cement matrix and their
  relative proportions
• The American Concrete Institute allows the
  modulus of elasticity to be calculated using the
  following equation
• where
• wc weight of concrete (pounds per cubic foot)
  and where
• f'c compressive strength of concrete at 28 days
  (psi)

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Cracking

• All concrete structures will crack to some
  extent.
• Cracks due to tensile stress induced by shrinkage
  or stresses occurring during setting or use

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Shrinkage cracking

• Occur when concrete members undergo restrained
  volumetric changes (shrinkage) as a result of
  either drying, autogenous shrinkage or thermal
  effects.
• The number and width of shrinkage
• cracks that develop are influenced by
• -the amount of shrinkage that occurs
• -the amount of restraint present
• -the amount and spacing of reinforcement
  provided.

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Tension cracking

• Most common in concrete beams where a
  transversely applied load will put one surface
  into compression and the opposite surface into
  tension due to induced bending.
• The size and length of cracks is dependent on
• - The magnitude of the bending moment
• - The design of the reinforcing in the beam at
  the point under consideration.

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Types of concrete

• Regular concrete
• High-strength concrete
• Stamped concrete
• High-performance concrete
• Self-consolidating concretes
• Vacuum concretes
• Shotcrete
• Pervious concrete
• Cellular concrete,
• Cork-cement composites
• Roller-compacted concrete

• Glass concrete
• Asphalt concrete
• Rapid strength concrete
• Rubberized concrete
• Polymer concrete
• Geopolymer or green concrete
• Limecrete
• Refractory Cement
• Concrete cloth
• Innovative mixtures
• Gypsum concrete

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Concrete testing

• Compression testing of a concrete cylinder
• Same cylinder after failure

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pg
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eakageCylinder.jpg
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General test methods

• Compaction Factor Test (Compacting Factor Test,
  Glanville)
• Compaction Test
• Free Orifice Test (Orimet Test)
• K-Slump Tester
• Free Flow Test Methods
• Slump Test
• Modified Slump Test
• Slump Rate Machine
• Kelly Ball Test
• Ring Penetration Test

• Cone Penetration Test
• Moving Sphere Viscometer
• Flow Trough Test
• Delivery-Chute Torque Meter
• Delivery-Chute Depth Meter
• Surface Settlement Test

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Concrete recycling

• increasingly common method of disposing of
  concrete structures
• recycling is increasing due to
• -improved environmental awareness
• - governmental laws
• -economic benefits
• Recycling concrete provides
• -environmental benefits
• -conserving landfill space

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Construction materials

• Asphalt
• Aggregate
• Brick
• Gypsum

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ASPHALT

• Also known as bitumen
• Dark brown to black
• Highly viscous
• Hydrocarbon produced from petroleum distillation
  residue. 
• At least 80 carbon, which explains its deep
  black color.
• Sulphur is another ingredient.
• Primarily used as a sealant for rooftops and a
  durable surface for roads, airport runways,
  playgrounds and parking lots.

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08/05/asfalt.jpg
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ASPHALT

• Asphalt can be separated from the other
  components in crude oil
• By the process of fractional distillation,
  usually under vacuum conditions.

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as/fractional_distillation_column2.jpg
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TYPES OF ASPHALT

• The major types of asphalt used in construction
  are
• Rolled asphalt
• Mastic asphalt.

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ne/rolled.jpg
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A.jpg
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Rolled Asphalt

• Made of aggregate, or solid materials such as
  sand, gravel, or recycled concrete, with an
  asphalt binder.
• Used to make roads and other surfaces, such as
  parking lots, by being applied in layers and
  compacted.
• Different types of rolled asphalt are
  distinguished according to the process used to
  bind the aggregate with the asphalt.

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TYPES OF ROLLED ASPHALT

• Hot mix asphalt concrete (HMAC)
• - Produced at 160 degrees Celsius.
• -This high temperature serves to decrease
  viscosity and moisture during the manufacturing
  process, resulting in a very durable material.
• -HMAC is most commonly used for high-traffic
  areas, such as busy highways and airports.

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ing-repair.jpg
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ROLLED ASPHALT

• Warm mix asphalt concrete (WAM or WMA)
• -Reduces the temperature required for
  manufacture by adding asphalt emulsions, waxes,
  or zeolites.
• -Benefits both the environment and the workers,
  as it results in less fossil fuel consumption and
  reduced emission of fumes.

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Small.jpg
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ROLLED ASPHALT

• Cold mix asphalt concrete,
• -Emulsified in soapy water before mixing it
  with the aggregate, eliminating the need for high
  temperatures altogether.
• -The asphalt produced is not nearly as durable
  as HMAC or WAM
• -Typically used for low traffic areas or to
  patch damaged HMAC.

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ic/images/coldmix.jpg
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ROLLED ASPHALT

• Cut-back asphalt concrete
• -Illegal in the United states since the 1970s,
  but many other countries around the world still
  use it.
• -The least environmentally friendly option,
  resulting in significantly more air pollution
  than the other forms.
• -Made by dissolving the asphalt binder in
  kerosene beforemixing it with the aggregate,
  reducing viscosity while the concrete is layered
  and compacted.

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MASTIC ASPHALT

• Also called sheet asphalt.
• Lower bitumen content than the rolled asphalt.
• Used for some roads and footpaths.
• Used also in roofing and flooring
• .

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MASTIC ASPHALT

• Stone mastic asphalt (SMA), is another variety.
• Becoming increasingly popular as an alternative
  to rolled asphalt.
• Benefits include
• -Anti-skid property
• -The absence of air pockets
• But if laid improperly
• -May cause slippery road conditions.

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PHYSICAL PROPERTIES OF ASPHALT

• Durability
• -  A measure of how asphalt binder physical
  properties change with age.
• - Sometimes called age hardening
• .  - In general, as an asphalt binder ages, its
  viscosity increases and it becomes more stiff and
  brittle.

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PHYSICAL PROPERTIES OF ASPHALT

• Rheology 
• The study of deformation and flow of matter. 
• Deformation and flow of the asphalt binder in HMA
  is important in HMA performance. 
• HMA pavements that deform and flow too much may
  be susceptible to rutting and bleeding, while
  those that are too stiff may be susceptible to
  fatigue cracking. 

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PHYSICAL PROPERTIES OF ASPHALT

• Safety
• Asphalt cement like most other materials,
  volatilizes (gives off vapor) when heated. 
• Flash point.
• For safety reasons, the flash point of asphalt
  cement is tested and controlled.
• Purity. 
• Asphalt cement, as used in HMA paving, should
  consist of almost pure bitumen. 
• Impurities are not active cementing constituents
  and may be harmful to asphalt performance. 

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AGGREGATE

• Collective term for sand, gravel and crushed
  stone mineral materials in their natural or
  processed state
• Roads and highways constitute the largest single
  use of aggregate at 40 percent of the total

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AGGREGATE ORIGINS AND PRODUCTION

• Can either be natural or manufactured
• Natural aggregates are generally extracted from
  larger rock formations through an open excavation
• Manufactured rock typically consists of
  industrial byproducts such as slag (byproduct of
  the metallurgical processing typically produced
  from processing steel, tin and copper)
• Specialty rock that is produced to have a
  particular physical characteristic not found in
  natural rock (such as the low density of
  lightweight aggregate). 

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AGGREGATE PHYSICAL PROPERTIES

• Toughness and abrasion resistance.  Aggregates
  should be hard and tough enough to resist
  crushing, degradation and disintegration from
  activities such as  manufacturing, stockpiling,
  production, placing and compaction. 
• Durability and soundness.  Aggregates must be
  resistant to breakdown and disintegration from
  weathering (wetting/drying) or else they may
  break apart and cause premature pavement
  distress. 

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• Particle shape and surface texture.  Particle
  shape and surface texture are important for
  proper compaction, load resistance and
  workability.  Generally, cubic angular-shaped
  particles with a rough surface texture are best. 
  
• Specific gravity.  Aggregate specific gravity is
  useful in making weight-volume conversions and in
  calculating the void content in compacted Hot
  Mixed Asphalt
• Cleanliness and deleterious materials. 
  Aggregates must be relatively clean when used in
  HMA.  Vegetation, soft particles, clay lumps,
  excess dust and vegetable matter may affect
  performance by quickly degrading, which causes a
  loss of structural support and/or prevents
  binder-aggregate bonding

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GYPSUM

• Occurs in nature as
• - flattened
• - often twinned crystals - transparent
  cleavable masses called selenite.
• May also occur in a silky, fibrous form, in which
  case it is commonly called satin spar.
• Finally may also be granular or quite compact.
• In hand-sized samples.
• Can be transparent or opaque.

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OCCURRENCE GYPSUM

• A common mineral, with thick and extensive
  evaporite beds in association with sedimentary
  rocks.
• Gypsum is deposited in lake and sea water.
• Hydrothermal anhydrite in veins is commonly
  hydrated to gypsum by groundwater in near surface
  exposures.
• Often associated with the minerals halite and
  sulfur.

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USES OF GYPSUM

• Gypsum Board primarily used as a finish for walls
  and ceilings known in construction slang as
  Drywall
• Plaster ingredient.
• A component of Portland cement used to prevent
  flash setting of concrete.

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BRICK

• Masonry unit
• Does not infer any particular material
• About 90 of UK, bricks made from
• some form of clay.
• 8 of UK bricks made of concrete
• crushed rock aggregate and portland
• cement are main constituents.
• 3 of UK of brick made from sand and lime,
• sometimes with the addition of crushed flint.

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l_web.jpg
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REFERENCES

• WEB,http//www.fhwa.dot.gov/infrastructure/materia
  lsgrp/cement.html
• WEB ,http//www.concrete.org/general/fE4-03.pdf
• WEB,http//architecture.arqhys.com/construction/pr
  operties-asphalt.html
• WEB,http//www.cement.org/basics/concretebasics_ag
  gregate.asp
• Standard specification for portland cement
  (AASHTO M 85-89). 1986. AASHTO standard
  specification for transportation materials. Part
  I, Specifications. 14th ed.
• Powers, T. C., L. E. Copeland, J. C. Hayes, and
  H. M. Mann. 1954. Permeability of portland cement
  paste. ACl Journal Proceedings 51 (3)285-98.
• Whiting, D. 1988. Permeability of selected
  concretes. ACI special publication. Permeability
  of concrete SP-108 195-222.
• Tsuji, Y., and N. Miyake. 1988. Chemically
  prestressed precast concrete box culverts.
  Concrete International Design and Construction
  10 (5)76-82 (May).
• Ramachandran, V. S., and R. F. Feldman. 1984.
  Cement science. In Concrete admixtures handbook
  Properties, science, and technology, ed. V.
  Ramachandran, 1-54. Park Ridge, N.J. Noyes
  Publications.

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Thank you for your attention?

• Simple question about our presentation.
• What is the composition of concrete?
• What is the purpose of curing?
• What is the types of asphalt mostly used in
  construction?
• What type of construction material is used for
  lining the kilns?

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Wood An Ancient building Material

• By
• Engr. Dr. Attaullah Shah

SWEDISH COLLEGE OF ENGINEERING AND TECHNOLOGY

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Wood
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Wood and Timber

• Wood is a hard, fibrous tissue found in many
  plants. It has been used for centuries for both
  fuel and as a construction material for several
  types of living areas such as houses, known as
  carpentry.
• In the United Kingdom and Australia, timber is a
  term also used for sawn wood products (that is,
  boards), whereas generally in the United States
  and Canada, the product of timber cut into boards
  is referred to as lumber.
• Throughout history, the unique characteristics
  and comparative abundance of wood have made it a
  natural material for homes and other structures,
  furniture, tools, vehicles, and decorative
  objects.
• Today, for the same reasons, wood is prized for
  a multitude of uses.
• Types
• Wood suitable for buildings Timber
• Woof of fallen tree Rough Timber
• Sawed and finished wood Converted Timber /Lumber
• All wood is composed of cellulose, lignin,
  hemicelluloses, and minor amounts (5 to 10) of
  extraneous materials contained in a cellular
  structure.

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Types of Trees

• Exogenous Trees/ Endogenous
• Exogenous Trees
• Grow in girth and material contained in the bark.
  
• Most of the building wood
• In the form of concentric rings called Annual
  rings
• Normally one rings represents one year growth
• Endogenous Trees
• Grows inwards by adding every year a fresh layer
  of internally
• The older formation are outside
• Flexible and slender and not fit for buildings
• Deciduous/Evergreen Trees
• Shed their leaves each winter Building wood
  mostly
• Evergreen
• Dont shed leaves every winter

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X-section of tree Bark, Wood, Branches, and
Cambium

• Cross section of white oak tree trunk
• (A) outer bark (dry dead tissue)
• outer corky dead part (A), whose thickness varies
  greatly with species and age of trees
• (B) inner bark (living tissue)
• which carries food from the leaves to growing
  parts of the tree
• (C) cambium
• Outer ring between the sapwood and bark
• Lighter, weaker and vulnerable to decay.
• (D) sapwood
• Transmits the sap from roots to branches
• (E) heartwood, (F) pith, and (G) wood rays.

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Sapwood and Heartwood

• Sapwood is located between the cambium and
  heartwood
• Sapwood contains both living and dead cells and
  functions primarily in the storage of food
• In the outer layers near the cambium, sapwood
  handles the transport of water or sap. The
  sapwood may vary in thickness and number of
  growth rings.
• Sapwood commonly ranges from 4 to 6 cm (1-1/2 to
  2 in.) in radial thickness.
• In certain species, the sapwood contains few
  growth rings and usually does not exceed 1 cm
  (1/2 in.).
• As a rule, the more vigorously growing trees have
  wider sapwood. Many second-growth trees of
  merchantable size consist mostly of sapwood.
• .

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• In general, heartwood consists of inactive cells
  that function in either water conduction or food
  storage.
• The transition from sapwood to heartwood is
  accompanied by an increase in extractive content.
• Frequently, these extractives darken the
  heartwood and give species such as black walnut
  and cherry their characteristic color

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Growth Rings

• In most species in temperate climates, the
  difference between wood that is formed early in a
  growing season and that formed later is
  sufficient to produce well-marked annual growth
  rings.
• The age of a tree at the stump or the age at any
  cross section of the trunk may be determined by
  counting these rings.
• However, if the growth in diameter is
  interrupted, by drought or defoliation by insects
  for example, more than one ring may be formed in
  the same season.
• In such an event, the inner rings usually do not
  have sharply defined boundaries and are termed
  false rings.
• Trees that have only very small crowns or that
  have accidentally lost most of their foliage may
  form an incomplete growth layer, some times
  called a discontinuous ring.

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Cross section of pine log showing growth rings.
Light bands are early wood , dark bands latewood.
An annual (growth) ring is composed of an inner
early wood zone and outer latewood zone.
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Cutting and Sawing Lumber
Shrinkage, distortion, and warpage of lumber
depends partially on the way lumber is cut from a
tree. Wood shrinks most in the direction of the
annual growth rings (tangentially) less across
these rings (radially) and very little parallel
to the grain (longitudinally).
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Cutting and Sawing Lumber
Lumber can be cut from a log in two different
ways tangent to the annual rings, called
plain-sawed in hardwoods and flat-grained or
slain-grained in softwoods. Lumber cut radially
to the annual rings is called quarter-sawed in
hardwoods, and edge-grained or vertical-grained
in softwoods.
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Cutting and Sawing Lumber
Lumber is classified as quarter-sawed if the
grain is 45 degrees to 90 degrees to the wide
face and plain-sawed if the grain is 0 degrees to
45 degrees to the wide face.
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Cutting and Sawing Lumber

• Characteristics of plain-sawed lumber include
• Distinct grain pattern,
• May twist, cup, or wear unevenly,
• Tends to have a raised grain,
• Shrinks and swells more in width, less in
  thickness,
• Less waste in cutting, and therefore less
  expensive.

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Cutting and Sawing Lumber

• Characteristics of Quarter-sawed lumber include
• Relatively even grain pattern,
• Wears evenly with less warpage,
• Shrinks and swells more in thickness, less in
  width,
• More waste in cutting and therefore more costly.

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Wood Defects

• Variety of defects that affect the strength,
  appearance, use, and grading of lumber. Defects
  may be natural or caused by manufacturing.
• Wood can be damaged by insects, decayed by
  fungus, and of course, destroyed by fire.

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Wood Defects
Knot branch embedded in a tree and cut through
manufacturing. Shake pitted area sometimes found
in cedar and cypress. Pitched Pocket opening
between growth rings and containing resin.
Check lengthwise grain separation caused by
seasoning. Split lengthwise separation of wood
extending from one face to another. Wane lack of
wood on the edge or corner. Warp shrinkage
distortion of a plane surface, includes---bow,
crook, cup and twist.
NATURAL DEFECTS
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Seasoning of wood

• seasoning is process of drying out timber after
  conversion. (Conversion felled trees are
  converted in sawmills into thick plank sizes).
• Freshly cut wood contains considerable water,
  which amounts to from one-third to more than
  one-half of the total weight.
• The drying of wood before it is processed into
  timber is called seasoning, and is done for a
  number of reasons. Seasoned wood is far more
  resistant to decay than fresh wood

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• it is much lighter and therefore less expensive
  to ship it has much higher heating value, which
  is important if it is to be used as fuel and,
  most important, wood changes in shape during
  drying, and this change in shape should be
  completed before the wood is worked or used.
• Wood may be seasoned either by air-drying or
  kiln-drying. Air-drying takes several months,
  whereas kiln-drying takes a few days. In both
  cases, the wood must be carefully stacked to
  prevent warping, and the rate of drying must be
  carefully controlled.

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Wood Seasoning Methods
Air Seasoning the natural method. Boards are
stacked in the open air with sticks (thin strips
of wood) between them to allow air to circulate.
The stack is raised clear of the ground on piers
and has a roof to protect it from the
weather. The ends of the boards are painted, or
have cleats (wood or metal strips) nailed across
them to prevent the end grain drying more quickly
than the rest of the board, as this causes
splitting (checking).
Advantages. It is cheap and needs little skilled
attention.Disadvantages. It takes 3 to 6 years
to dry.The moisture content can only be reduced
to 15 18 by air seasoning.
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• Kiln Seasoning the artificial method. Boards
  are stacked on trolleys with sticks between them,
  and pushed into a kiln. The kiln is sealed and
  seasoning proceeds in three stages.
• Stage 1. Steam is injected at low temperature to
  force free moisture out of the wood cells.
• Stage 2. Steam is reduced and the temperature is
  increased to dry the wood
• Stage 3. Finally there is a flow of hot, almost
  dry, air.

Advantages. It takes only a few days or weeks
and kills insect eggs in the wood (e.g.
woodworm). It is possible to reduce moisture
content to below 12, making the wood suitable
for use in centrally heated and air-conditioned
buildings
Disadvantages. Kilns are expensive to build and
to run.It needs a more attention and a lot of
skill as incorrect drying will ruin he wood.
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• Water seasoning
• Large logs are immersed in water for 15 days.
• Later dried in the open air.
• Suitable for wood containing more sap.
• Not suitable where strength is required like
  structural uses.
• Most of the fermentable matters removed and wood
  less vulnerable to attacks of worms.
• Chemical seasoning or salt seasoning
• Timber soaked in the solution of urea.
• Later dried in kiln.
• Electric seasoning
• Quick but expensive.
• High frequency AC currents passed in the wood.

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Characteristics of good Timber

• Quality of timber depends on
• Species used, the soil where tree is grown, time
  of felling and methods of seasoning and
  treatment.
• Free of defects like knots, wanes, etc.
• Obtained from hearth of sound treed and sap
  removed.
• Uniform structure and color.
• Narrow annual rings.
• Heavier in weight
• Firm adhesion of fibers.

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Causes of wood decay and preservation

• Wood is naturally a very durable substance. If
  not attacked by living organisms, it will last
  for hundreds or even thousands of years.
• Samples of wood used by the ancient Romans have
  been found virtually in their original condition
  when a combination of circumstances protected
  them against attack.
• The most important of the organisms attacking
  wood are the fungi that cause so-called dry rot,
  which actually occurs only when the wood is damp.
• The sapwood of all trees is susceptible to this
  type of decay, but the heartwood of a few species
  is naturally resistant to these fungi. Walnut,
  redwood, cedar, mahogany, and teak are among the
  well-known woods that are extremely durable
• Other woods are resistant to various types of
  attack. Greenheart and teak are particularly
  resistant to the attack of marine borers, and so
  are often used for underwater construction for
  wharves.
• A number of woods are comparatively resistant to
  termites, including redwood, black walnut,
  mahogany, and several types of cedar.
• In most of these cases, the woods are aromatic,
  and the resistance is probably due to the resins
  and similar chemicals they contain.

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• Wood may be preserved by protecting it chemically
  against deterioration. The most important method
  of treatment has long been impregnation with
  creosote or zinc chloride.
• This method is still one of the best, although a
  number of newer chemicals, notably several
  containing copper compounds, have been introduced
  for the same purpose. Wood can be protected
  against weathering by suitable surface coatings,
  applied by brushing, spraying, or dipping.
  Surface applications yield little penetration,
  however, and therefore do not prevent
  deterioration under attack by insects, fungi, or
  borers.
• By applying a finish to wood we not only protect
  it but tend to improve its appearance. A highly
  polished dining table or floor is not only safe
  from attack by organisms and chemicals they
  become more attractive or aesthetically pleasing.
  New paints and coatings are constantly being
  developed to improve and enhance the appearance
  and properties of both natural and processed wood
  

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• Commonly used wood preservation techniques
• A good preservative must be
• Cheap - Easy to use and handle - Non injurious to
  the tissues of trees- Should preserve permanently
  and must not wash.
• Should not affect the color of the wood.
• Methods of Preservation
• Brush treatment and painting
• 2-4 coats of oil, paint or creosote
• Charring of timber
• Charring the outer fibers of timber by fire
• Envelop of charcoal is devoid of food and
  restricts fungi.
• Reduces the strength as burns the outer fibers.
• Dipping
• Dipped in preservative and soaked for few
  minutes.
• Used for lower ends of poles and wooden piles.
• Creosoting
• Moisture extracted and the vacuum filled with
  creosote
• Creosote is by-product coal tar produced in
  manufacture of coal gas

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Engineered Wood Products

• OSB
• LVL
• Plywood
• Particle Board
• Glulam
• MDF
• I-Beams
• Trusses

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Particle Boardmanufactured from wood particles,
such as wood chips, sawmill shavings, or even saw
dust. Made with larger pieces of wood than used
to make MDF
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Chipboard or Particleboard
Most chipboard is of graded density, having
smaller chips packed tightly together on the
outside to give a smoother and stronger face.
Chipboard is made by gluing wooden chips together
under heat and pressure.
It is suitable only for interior use. Veneered
and melamine-faced chipboard is widely used for
worktops, shelves and furniture making.
Usual sheet size is 2240 x 1220mm. Common
thicknesses are 12mm and 18mm.
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Blockboard and Laminboard
These are made by sandwiching strips of softwood
between two plies. The strips are narrower in
laminboard than in blockboard.
They are usually made in interior grade only. The
grain of the face plies runs at right angles to
the core strips. The core strips are arranged
with the heartside alternately on top and
underneath (as when edge jointing boards) to
avoid warping.
Both block and laminboard can be faced with
veneers of decorative hardwood. It is usually
cheaper to make blockboard than to make multiply
over 12 mm thick.
Usual sheet size is 2440 x 1220mm. Common
thickness is 18mm.
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Hardboard
Hardboard is made by mixing wood fibres with
water and synthetic resin glue, hot-pressing it
into sheets and leaving it to dry.
It is not very strong and is usually fixed onto a
wooden frame.
Standard grade is for interior use. Tempered
grade is impregnated with oil for exterior use
and for bending to make curved shapes. Can be
melamine-faced or ready painted.
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Medium Density Fibreboard (MDF)
A fairly new material (1979) but extensively used
that is like a very smooth chipboard.
Fibreboard is made from a pulp of wood or other
vegetable fibres which is dried under heat and
pressure.
For adhesion it relies principally on the natural
resin contained in the pulp.
It is used for model-making, light structural
items such as speaker cabinets and extensively
for furniture wardrobes kitchen units etc.
Usual sheet size is 2240 x 1220mm but may be
supplied in half or quarter sheets. MDF is
available in a large range off thickness from 5mm
to over 50mm.
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Oriented Strand Board (OSB)
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Oriented Strand Board (OSB)
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Laminate Strand Lumber (LSL)Made up of strands
of lumber instead of veneers
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Laminated Veneer Lumber (LVL) LVL is made by
gluing sheets of veneer together. Unlike plywood,
here all veneer layers are going in the same
direction. Wide panels are manufactured to the
thickness of the desired lumber. The panels are
ripped into lumber of nominal width.
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Masonite Type of hardboard invented by
William H. Mason. It is formed using the Mason
method, using wooden chips and blasting them into
long fibers with steam and then forming them into
boards. The boards are then pressed and heated to
form the finished boards. No glue or other
material is added.
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Plywood made from thin sheets of wood veneer,
called plies or veneers, layered in opposite
directions
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WOOD MATERIAL THEORY
Plywood
This is made from layers or plies of wood glued
together so that the grain of each ply is at
right angles to the next. There is always an odd
number of plies so that the grain runs the same
way on both outside pieces and hence stresses are
balanced.
Traditional 5- ply plywood
Direction of layers at 90 degrees to each other
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WOOD MATERIAL THEORY
Plywood can be faced with a veneer of decorative
hardwood to improve its appearance, or with
melamine to give a harder wearing surface.
Plywood is graded for interior or exterior use
depending on the water resistance of the glue
used, and this is shown by code letters on each
sheet.
WBP Weather and boil proof.
BR Boil resistant
MR Moisture resistant
Int. Interior use only
Plywood is also graded by the smoothness of the
surface and number of defects in it.
Plywood can be nailed near the edge without
splitting. Thin plywood is flexible and can be
formed into curved shapes.
Usual sheet sizes are 2440 x 1220mm and 1525 x
1525mm. Common thicknesses are 4, 6, 9 and 12 mm.
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Wood I-BeamsVeneer lumber is used for the
flanges and plywood or OSB is used for the web to
resist shear.
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Glued Laminated Lumber (Glulam) These beams are
made by gluing many boards together to form a
structural member bigger than the trees from
which the board were sawn. Since the load is
carried by the material in the top and bottom
faces and the middle only has to resist shear,
high quality lumber is used in the top and bottom
while medium grade lumber is used in the center.
(gluelam or glulam) Joints between boards are
typically scarf of finger joints.
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Wood Trusses
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Important Wood types

• Deodar ( Cedrus Deodara)
• Kail ( Biar) or Blue Pine ( Pinus excelsa)
• Chir ( Pine) ( Pinus Longifolia)
• Bamboo or Bans ( Bambusa).
• Jaman
• Mango
• Neem
• Olive
• Phulai
• Shishum ( Tali)
• Teak or Sagwan.

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Group Assignment

• G-1 Write the names of most commonly used two
  softwoods and two hardwoods. Explain their
  properties and uses in Civil Engineering.
• G-2 Explain various methods for seasoning of
  wood.
• G-3 Types and uses of Engineered Wood
• G-4 Structural uses of Wood in Civil Engineering
  
• G-5 Characteristics of Good Quality Wood.
• G-6 Compare Plywood and Laminated Veneered
  Lumber ( LVL)
• G-7 Common Types of Defects in Wood and their
  remedies