CONSTRUCTION
MATERIALS
Role of Material Science in CE
 Combining
several sciences
 Chemistry
 Physics
 Mechanics
 Behavioral
understanding of
materials is based on knowledge of
these sciences.
Predicting Behavior
 Civil
Engineers design complex
systems using relationships between
 Stress
vs. Strength
 Strain vs. Deflection
 Exposure vs. Durability
 Risk vs. Consequence
 Cost vs. Aesthetics & Life Cycle
 Others
Materials Science
 Atomic
nature of materials
 Microstructure
 Relationship between material structure
and engineering properties
 Altered structures to customize properties
Construction Materials
 Concrete
 Steel
 Timber
Concrete (Beton)
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The word concrete comes from the Latin word
"concretus" (meaning compact or condensed), the
perfect passive participle of "concrescere", from
"con-" (together) and "crescere" (to grow)
Concrete is a composite material composed mainly
of water, aggregate, and cement.
In concrete, there is approximately:
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10% cement
20% water and air
30% sand
40% gravel
by volume
 In Turkish the Word ‘beton’ comes from French.
Concrete
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Concrete is an easily shaped construction material.
Before setting, fresh concrete is as soft and viscous as
a clay paste.
Over time, the cement forms a hard matrix which
binds the rest of the ingredients together into a
durable stone-like material with many uses.
When cement, water and aggregates are mixed
together, they form a fluid mass that is easily molded
into shapes makes concrete a very practical and
useful construction material compared to timber and
stone.
It can be both produced in a factory or at the site.
Concrete
Properties of concrete
Compressive strength
35 MPa
Bending strength
Tensile strength
Elasticity Modulus
Poisson’s Ratio
Shrinkage
Density
High density concrete
Normal concrete
Lightweight concrete
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6 MPa
3 MPa
28000 Mpa
0.2
0.005 – 0.1 %
>2800 kg/m3
2350 kg/m3
1800 kg/m3
The decrease in volume of the concrete after pouring the concrete is
called shrinkage (rötre in Turkish).
The main reason for shrinkage is loss of water.
While the fresh concrete is still plastic, the excess water comes to the
surface and evaporates. Some of the water is also used in chemical
bonds. Therefore, too much water is lost at a very short time.
Concrete
Concrete must both have
 high mechanical strength.
 Durability (to the chemical external effects)
Concrete is classified according to their compressive strength.
Concrete Class
28-day compressive
strength
(cylinder)
(N/mm2)
28-day compressive
strength
(cube)
(N/mm2)
C-14
C-16
C-18
C-20
C-25
C-30
C-35
C-40
C-45
C-50
C-55
C-60
C-70
C-80
C-90
C-100
14
16
18
20
25
30
35
40
45
50
55
60
70
80
90
100
16
20
22
25
30
37
45
50
55
60
67
75
85
95
105
115
Concrete
 The interesting point about concrete is that the tensile
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strength of concrete is very small compared to the
compressive strength.
For this reason, the reinforcement bars (steel) is used.
Steel has a high tensile strength
and may elongate under high
tensile forces.
Unit deformation(strain)
Compression
stress
(Shortening)
(Elongation)
Tension
stress
Behaviour of Reinforced Concrete
Materials
Reinforced concrete
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Concrete and steel is coherent to each other.
So reinforced concrete (betonarme) structures can be built.
After setting, the concrete and the steel work together as if they are only
one material.
They react the temperature changes similarly (their thermal expansion
coefficients are close to each other.)
Otherwise, the use of reinforced concrete structures will be very limited.
Brittle Behavior
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A material is brittle if, when subjected to stress, it
breaks without significant deformation (strain).
Brittle materials absorb relatively little energy prior
to fracture, even those of high strength.
Breaking is often accompanied by a snapping
sound.
Brittle materials include most ceramics and
glasses (which do not deform plastically) and
some polymers.
Ductile Behavior
 In
materials science, ductility is a solid
material's ability to deform under tensile
stress; this is often characterized by the
material's ability to be stretched into a
wire.
OR
 The response to stress of certain materials
which undergo permanent deformation
without fracturing
Brittle and Ductile Behavior
Schematic appearance of round metal bars after tensile testing.
a) Brittle fracture
b) Ductile fracture
c) Completely ductile fracture
Brittle and Ductile Behavior
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We want the reinforced concrete structural
elements to behave ductile. Because under
earthquake loads, when the load bearing
capacity of the elements are exceeded, the
ductile elements can make large deformations
without failure and absorb the earthquake
energy.
A structural elements behaves elastically up to a
certain limit, then it begins to crack (a permanent
deformation). After cracking begins, the amount
of deformation at the element is a sign of its
ductility or brittleness.
Brittle and
Ductile
Behavior
Material Behavior
Steel
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All purpose
Durable
Ductile
Material of the modern life
Steel is built with changing the amount of carbon in
iron.
There is a high amount of carbon in iron.
We have to reduce this amount.
Every production has its own recipe. (the beam of a
skyscraper, a submarine or a knife different steel
types.)
Steel
 Raw
iron has 5% Carbon
 Steel has 0.16 – 0.20 % Carbon
 Increasing carbon amount, increases the strength
and rigidity of steel.
 Iron and steel is being used for 5000 years. But
they are used for the construction industry first in
18th century in England.
 First structures built using iron are bridges.
 Steel used in the structures today has a crystal
formation, it is isotropic and homogeneous.
Mechanical properties of steel is determined by steel tensile tests.
Tensile tests are conducted in tensile test machines, providing
controlled uniformly increasing tension force, applied to the specimen.
As the force increases, the length of the sample increases and the
cross-sectional area decreases. The force is increases until the bar
cracks. The elongation and stress values during the test are determined
and a stress-strain curve is drawn.
Steel for Reinforced Concrete Structures
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As the tensile strength of concrete is too
low, steel is used where there are tensile
stresses.
Additionally it is used as stirrups.
First reinforcement is done in 1850.
Reinforcement bars have circular cross
sections. The surface can be either plain
or deformed.
Deformed bar has higher strength and
locks into the concrete better than the
plain ones.
Plain bars have a limited use in Turkey
after 2007 Earthquake Code.
Deformed bars are welded as a mesh
and they are used in large surface areas
such as floors, tunnels and concrete
roads.