1. CONSTRUCTION MATERIALS

2. Role of Material Science in CE
Combining several sciences
Chemistry
Physics
Mechanics
Behavioral understanding of materials is based on knowledge of these sciences.

3. 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

4. Materials Science Atomic nature of materials Microstructure
Relationship between material structure and engineering properties
Altered structures to customize properties

5. Construction Materials
Concrete
Steel
Timber

6. Concrete (Beton)
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:
10% cement
20% water and air
30% sand
40% gravel
by volume
In Turkish the Word ‘beton’ comes from French.

7. Concrete 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.

8. Properties of concrete
Compressive strength
35 MPa
Bending strength
6 MPa
Tensile strength
3 MPa
Elasticity Modulus
28000 Mpa
Poisson’s Ratio
0.2
Shrinkage
0.005 – 0.1 %
Density
High density concrete
>2800 kg/m3
Normal concrete
2350 kg/m3
Lightweight concrete
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.

9. 28-day compressive strength
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)
(cube)
C-14 14 16
C-16 20
C-18 18 22
C-20 25
C-25 30
C-30 37
C-35 35 45
C-40 40 50
C-45 55
C-50 60
C-55 67
C-60 75
C-70 70 85
C-80 80 95
C-90 90
105
C-100
100
115

10. Concrete
The interesting point about concrete is that the tensile strength of concrete is very small compared to the compressive strength.
For this reason, the reinforcement bars (steel) is used.

11. Steel has a high tensile strength and may elongate under high tensile forces.
Compression stress
Unit deformation(strain)
(Shortening)
(Elongation)
Tension
stress

12. Behaviour of Reinforced Concrete Materials

13. Reinforced concrete 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.

14. Brittle Behavior
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.

15. 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

16. Brittle and Ductile Behavior
Schematic appearance of round metal bars after tensile testing.
Brittle fracture
Ductile fracture
Completely ductile fracture

17. Brittle and Ductile Behavior
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.

18. Brittle and Ductile Behavior

19. Material Behavior

20. Steel All purpose Durable Ductile
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.)
Material of the modern life

21. 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.

26. 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.

27. Steel for Reinforced Concrete Structures
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.