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CONCRETE TECHNOLOGY

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CONCRETE TECHNOLOGY Dr. Ali I. Tayeh University of Palestine Dr. Ali I. Tayeh University of Palestine Concrete Technology * * * * * * Syllabus Mineral Admixtures and ... – PowerPoint PPT presentation

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Title: CONCRETE TECHNOLOGY


1
CONCRETE TECHNOLOGY
Dr. Ali I. Tayeh
2
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
3
Chapter 1
Concrete
Concrete as a Material
4
Concrete
  • Concrete as a Material
  • The Nature Of Concrete
  • Advantages Of Concrete
  • Limitation Of Concrete

5
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..

6
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.

7
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.
8
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
9
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.
10
The Nature Of Concrete
11
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.
12
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.

13
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.

14
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.

15
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.

16
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.

17
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.

18
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

19
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.

20
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.

21
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.

22
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.

23
  • End
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