CONCRETE TECHNOLOGY Dr. Ali I. Tayeh. SyllabusTopic ًً Date Lectures Outline: Introduction....
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Transcript of CONCRETE TECHNOLOGY Dr. Ali I. Tayeh. SyllabusTopic ًً Date Lectures Outline: Introduction....
CONCRETE TECHNOLOGY
Dr. Ali I. Tayeh
SyllabusSyllabus
Lectures Outline:
������DateDateTopicTopic
1st WeekIntroduction.Concrete as a material
2nd WeekCements
3rd WeekMineral Admixtures and Blended Cements
4th WeekWater.
5th WeekAggregates.
6th WeekFresh Concrete
7th WeekReview and Midterm Exam.
8th WeekProportioning Concrete Mixes
9th WeekHandling and placing.
10th WeekCuring and strength.
11th WeekTesting of Hardened Concrete
12th WeekDurability
13th WeekReview
14 th WeekFinal Exam
Chapter 1Chapter 1
ConcreteConcrete
Concrete as a Material
Concrete• Concrete as a Material
The Nature Of Concrete
Advantages Of Concrete
Limitation Of Concrete
• 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..
Concrete as a MaterialConcrete 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 "concretusconcretus,"
which means to grow together.
Concrete as a MaterialConcrete as a Material
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.
The Nature Of ConcreteThe 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
The Nature Of ConcreteThe 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 PortlandPortland throughout the
text and use a qualifying descriptor only when dealing
with other kinds of cement and concrete.
The Nature Of ConcreteThe Nature Of Concrete
The Nature Of ConcreteThe 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 PortlandPortland through out the
text and use a qualifying descriptor only when dealing
with other kinds of cement and concrete.
The Nature Of ConcreteThe Nature Of Concrete
Advantages Of ConcreteAdvantages 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.TypeTable 1.3.Type
• all properties of concrete are given in Table 1.4.Table 1.4.
Advantages Of ConcreteAdvantages 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 <10 MPa (1500 Ib/in.2) or > 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.
Advantages Of ConcreteAdvantages 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 (<1 cents/b).
• Furthermore. fabricating concrete on site, its
properties may be tailored for the specific application.
Advantages Of ConcreteAdvantages 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.
Advantages Of ConcreteAdvantages 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.
Advantages Of ConcreteAdvantages Of Concrete
The 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.
Advantages Of ConcreteAdvantages 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
Limitation Of ConcreteLimitation 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.
Limitation Of ConcreteLimitation 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.
Limitation Of ConcreteLimitation 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.
Limitation Of ConcreteLimitation 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.
End