CONCRETE TECHNOLOGY

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CONCRETE TECHNOLOGY
Dr. Ali I. Tayeh
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Syllabus
Topic ??Date Lectures Outline
Introduction. Concrete as a material 1st Week Lectures Outline
Cements 2nd Week Lectures Outline
Mineral Admixtures and Blended Cements 3rd Week Lectures Outline
Water. 4th Week Lectures Outline
Aggregates. 5th Week Lectures Outline
Fresh Concrete 6th Week Lectures Outline
Review and Midterm Exam. 7th Week Lectures Outline
Proportioning Concrete Mixes 8th Week Lectures Outline
Handling and placing. 9th Week Lectures Outline
Curing and strength. 10th Week Lectures Outline
Testing of Hardened Concrete 11th Week Lectures Outline
Durability 12th Week Lectures Outline
Review 13th Week Lectures Outline
Final Exam 14 th Week Lectures Outline
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Chapter 1
Concrete
Concrete as a Material
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Concrete

• Concrete as a Material

• The Nature Of Concrete

• Advantages Of Concrete

• Limitation Of Concrete

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Concrete as a Material

• Concrete is a material that literally forms the
  basis of our modern society. Scarcely any aspect
  of our daily lives does not depend directly or
  indirectly on concrete. We may live, work, study,
  or play in concrete structures to which we drive
  over concrete roads and bridges.
• Our goods may be transported by trucks traveling
  on concrete super high ways. by trains that run
  on rails supported on concrete crossties., by
  ships that moor at concrete piers in -harbors
  protected by concrete breakwaters, or by
  airplanes landing and taking off on concrete
  runways.
• Water drinking and for raising crops is stored
  behind massive concrete dams and is distributed
  by systems of concrete waterways., conduits., and
  pipes..

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Concrete as a Material

• Concrete plays a key role in oil production,
  being used to construct massive off shore
  platforms for drilling .
• We take concrete for granted in our everyday
  activities and tend to be impressed by the more
  dramatic impacts of technology.
• it can be truly said that many of the
  achievements of our modern civilization have
  depended on concrete, just as many of the
  enduring achievements of the earlier civilization
  of Rome were made possible by the use of the
  forerunner of modern concrete.
• The word concrete comes from the Latin verb
  "concretus," which means to grow together.

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The Nature Of Concrete
Concrete is a composite material composed of
coarse granular material (the aggregate or
filler) embedded in a hard matrix of material
(the cement or binder) that fills the space
between the aggregate particles and glues them
together. Aggregates can be obtained from many
different kinds of materials, although we mostly
make use of the materials of nature common rocks.
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The Nature Of Concrete
They are essentially inert, filler materials
that, for convenience. are separated into fine
and coarse factions. Similarly, the cement can be
formulated from many diverse chemicals. "Cement"'
is a generic term that can apply to all binders.
Therefore, descriptors must he used to qualify
this term when referring to specific materials. A
civi1 engineer may have cause to use
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The Nature Of Concrete
Portland cement concrete, calcium aluminates
cement concrete, or polymer concrete ,where the
binders are Portland cement, calcium aluminate
cement, or a polymer resin, respectively. In
concrete construction, the engineer will use
Portland cement concrete 95 of the time. Thus,
for convenience, we will often drop the name
Portland throughout the text and use a qualifying
descriptor only when dealing with other kinds of
cement and concrete.
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The Nature Of Concrete
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The Nature Of Concrete
Portland cement concrete, calcium aluminates
cement concrete, or polymer concrete ,where the
binders are Portland cement, calcium aluminate
cement, or a polymer resin, respectively. In
concrete construction, the engineer will use
Portland cement concrete 95 of the time. Thus,
for convenience, we will often drop the name
Portland through out the text and use a
qualifying descriptor only when dealing with
other kinds of cement and concrete.
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Advantages Of Concrete

• Concrete is the predominant material used in
  construction .
• It competes directly with all other major
  construction materials-timber, steel, asphalt,
  stone, etc.-
• The major advantages and disadvantages of
  concrete are summarized in Table 1.3.Type
• all properties of concrete are given in Table 1.4.

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Advantages Of Concrete

• concrete properties can vary significantly from
  the figures given, depending on the choice of
  materials and proportions of a particular
  application.
• For example, subsequent chapters will show how
  concrete can be designed to have compressive
  strengths lt10 MPa (1500 Ib/in.2) or gt 100 MPa
  (15,000lb/in.2) with concomitant changes in
  modulus of elasticity.
• The ability of concrete to be cast to any desired
  shape and configuration is an important
  characteristic that can offset other shortcomings.

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Advantages Of Concrete

• Concrete can be cast into soaring arches and
  columns, complex hyperbolic shells, or into
  massive, monolithic section used in dams, piers,
  and abutments. On-site.
• construction means that local materials can be
  used to a large extent, thereby keeping costs
  down. Cement costs only about 7-10 cents/kg (3--4
  cents/lb) (2001) and aggregates less than 2
  cents/kg (lt1 cents/b).
• Furthermore. fabricating concrete on site, its
  properties may be tailored for the specific
  application.

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Advantages Of Concrete

• On the other hand, on-site production is a mixed
  blessing because the quality of concrete must be
  carefully controlled. Environmental conditions
  fluctuate, so that it is difficult to assure
  uniform process41g of concrete throughout a job
• Constituent materials are less carefully
  characterized than they might be and can have
  undesirably high variations in properties. The
  use of an unskilled or semiskilled work force
  means that in the absence of proper supervision
  on the job site, undesirable practices they be
  adopted and tolerated.
• Casting of concrete can also be adapted to
  factory-controlled production.
• precast building elements for standardized low.
  cost building systems arc more common in European
  countries, but have also been developed in the
  United States.

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Advantages Of Concrete

• precast concrete block has become a very popular
  building element, and precast concrete pipe is
  widely used in drainage, sewage, and water-supply
  projects.
• precast, prestressed concrete beams, girders. and
  panels in various configurations are used
  increasingly in many structures.
• precast concrete can be produced more uniformly
  with closer tolerances compared to concrete cast
  on site, but requires a more skilled work force
  and generally more sophisticated equipment.
• Good Quality concrete is a very durable material
  and should remain maintenance free for many years
  when has been properly designed for the service
  conditions and properly placed.

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Advantages Of Concrete

• The Advantages Of Concrete
• It has a relatively high compressive strength.
• It has better resistance to fire than steel.
• It has a long service life with low maintenance
  cost.
• In some types of structures it is the most
  economical structure material as dam and footing.
• It is easy to form.
• It yields rigid members with minimum apparent
  deflection.

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Advantages Of Concrete

• Disadvantages Of Concrete
• It has a low tensile strength of about one tenth
  of its compressive strength.
• It needs mixing and curing all of which affect
  the finial strength of concrete.
• The cost of form which will be used in casting is
  high
• It has low compressive strength with respect to
  steel which lead to large section in columns of
  multistory buildings.
• Cracks develop in concrete due to shrinkage and
  application of live loads

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Limitation Of Concrete

• However, concrete does have weaknesses that may
  limit its use in certain applications and must be
  allowed for when designing structures.
• Concrete is a brittle material with very low
  tensile strength.
• Concrete should generally not be loaded in
  tension (except for low bending stresses that may
  be permitted in unreinforced slabs on grade), and
  reinforcing steel must be used to carry tensile
  loads inadvertent tensile loading causes
  cracking. The low ductility of concrete also
  means that concrete lacks impact strength and
  toughness compared to metals.

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Limitation Of Concrete

• Even in compression, concrete has a relatively
  low strength-to-weight ratio, and a high load
  capacity requires comparatively large masses of
  concrete, although, since concrete is low in
  cost, this is economically possible.
• The volume instability of concrete must also be
  allowed for in design and construction.
• It shows volume stability that is more
  characteristic of timber and quite unlike that of
  steel, which is a volume-stable material under
  normal conditions of service.

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Limitation Of Concrete

• Concrete undergoes considerable irreversible
  shrinkage due to moisture loss at ambient
  temperatures and also creeps significantly under
  an applied load even under conditions of normal
  service.
• Awareness of these problems with concrete enables
  us to compensate for them, by using suitable
  designs and by controlling them, in part, through
  a suitable choice of materials and construction
  practices.

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Limitation Of Concrete

• A great deal of research effort has been devoted
  to ameliorating these problems and now
  ready-mixed concrete with compressive strengths
  of 100 MPa (15,000 Ib/in.2) can be routinely
  produced in some areas.
• Over the last 30 years, new types of concrete
  have been developed, such as fiber. Reinforced
  concrete, shrinkage-compensated concrete,
• Cement based materials with flexural strengths
  exceeding 150 MPa (22,000 Ib/in.2) or with
  tensile
• strains greater than 1 have been produced.

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• End