Material -1.ppt

ADDIS ABABA SCIENCE AND
TECHNOLOGY
BSc. Program in Civil Eng.
Construction Materials
Habtamu E.
2023/24
Lecture – 1
Introduction
Nature and Properties of materials
1/21/2024

 Classification of Construction Materials
 Properties of Materials
 Behavior of materials under load
Chapter One
Department of Civil Engineering
Introduction

 Material: a substance or thing from which some thing else can be
made. Examples: Cement, brick, aluminum, soil, water…
 In Engineering, materials are employed to design and build
structures or elements.
 Material Engineering refers to the understanding and review of
properties and uses of materials commonly used in engineering
applications.
 Construction material???
Introduction
Lecture

A. Amorphous Materials
 Materials in which atoms are arranged randomly or those that
do not have crystalline structure.
Examples: Plastics, glass, rubber, metallic glass, polymers, …
B. Brittle Materials
 Shows relatively little or no elongation or increase in length at
fracture. Examples: cast iron, concrete, Glass…
Classification of Construction Materials

C. Building Materials:
Materials that are used in the building industry such as cement,
steel ,brick, plastics, wood, glass
D. Cementitious materials:
Materials in which the principal binder is Portland cement or
another type of hydraulic cements.
E. Ceramic Materials:
ceramic materials are nonmetallic materials based on clay(silicate
mineral)
They are usually crystalline and brittle, do not conduct electricity
very well, and can withstand high temperatures.
Cont……………..

F. Construction Materials: any material used in construction
industry. Examples: cement, soil, aggregates, asphalt, etc
G. Ductile Materials:
 that makes the material to be drawn out or stretched to a
considerable extent before rupture.
 It is usually measured as the percentage of elongation (increase
in length) or as the percentage of the reduction in the cross-
sectional area ,when the material is subjected to tension.
Examples :steel ,aluminum etc
Cont ……………………

H. Elastic Materials:
 it is the ability of a material to deform under load without a
permanent set or deformation up on release of the load.
 A perfectly elastic material recover completely its original shape
and dimensions when loads are removed.
 But all exhibit elastic properties up to some stress level.
 An elastic material behaves in elastically when the stresses
exceeds the elastic limit, beyond which changes in volume
,shape are permanent.
Cont………………….

I. Crystalline materials:
Materials in which atoms are arranged in a discernible repeated
pattern in three dimensions.
J. Thermoplastic Materials:
Materials that turn plastic (soft) when subjected to heat. e.g.
petroleum pitch
Cont………………….

 Materials that are used for construction purpose can be broadly
classified based on their:
 Metallic Property
 Physical nature
 Mode of production
Classification of Construction Materials
Lecture

 Construction materials can be classified into:
I. Metallic and Non-metallic
A. Non-metallic
 Cementing materials
 Concrete
 Timber
 Stone
 Plastics
 Ceramics
Cont…………………..

A. Metallic (ferrous metals contain iron and non-ferrous metals do not.)
1. Ferrous
 Wrought iron
 Cast iron
 Steel
2. Non Ferrous
 Aluminum
 Copper
 Lead
 Zinc
Cont…………….

II. Based on their physical Nature:
A. Solid
B. Liquid
C. Gaseous:
III. Based on their mode of manufacture:
A. Naturally occurring materials: stone, timber
B. Industrially produced materials: cement, glass
C. Materials produced at construction site: concrete, mortar
Cont………………………….

A. Physical properties
 Density and specific gravity
 Mechanical properties
 Porosity
 Permeability
 Thermal properties
 Acoustical properties
B. Chemical properties
 Corrosion
 Combustibility
 Toxicity
 Decay Resistance
Properties of Materials
Lecture

A. Mechanical Properties
 When forces are applied to a solid body, two results are produced:
 Internal resisting forces
 Deformation
 The internal forces and deformations are called stresses and
strains respectively.
 Depending up on the arrangement and direction of the external
forces, the stress produced may be:
Properties of Materials
Lecture
 Tensile stress
 Compressive stress
 Shearing stress
 Bending stress
 Torsional stress

A. Behavior of materials under load
 Application of external force on solid body in equilibrium results
in:
 Internal resisting forces are developed in the body which
balances the externally applied force.
 The body is deformed to varying degree
 The intensity of internal force is stress and the deformation
per unit is strain.

 Deformation:
 Elastic if it recovers when the external force is released. When the
material goes back to its original form, that's elastic deformation.
 Plastic if it fails to recover when the external force is released. When
energy goes into changing the shape of some material and it stays
changed, that is said to be plastic deformation.
Cont……

 Tests for Mechanical Properties
 Selection of material for a particular structural application
depends on its mechanical properties.
 There are standard mechanical tests to measure these properties.
 Mechanical tests are used to examine the performance of
materials under the action of external forces.
 Classification of Mechanical Tests
 With reference to the direction of the external forces:
Cont…………
a) Tension test
b) Bending test
c) Compression test
d) Torsion test
e) Shear test

 Tension Test
 Specimen under tension test is subjected to an axial tensile force
 Tensile stress is developed on cross-sectional area perpendicular
to the line of action of the force.
 The specimen increase /decrease in length.
Cont…………………

Addis Ababa Science & Technology
College of Architecture and Civil Engineering
 Compression Test
 Specimen is subjected to an axial compressive force
 Compressive stress is produced.
 The specimen decrease/ increase in length.
Cont………………………

 Shear test
 In this test, shearing stress is
determined on the x-sectional area
parallel to the line of action of the
external forces.
 Bending Test.
 Specimen is subjected to forces that
give rise to bending moments
 The resulting stresses are compressive
on one side of the neutral axis &
tensile on the other side.
Cont………………………..

Classification of Mechanical Tests
 With reference to the rate and duration of the load application:
a) Static Tests: these are made with gradually increasing load, such as ordinary
tests in tension, compression etc.
b) Dynamic test: these are made with suddenly applied loads, as by falling
weight
c) Wear tests: these are made to determine resistance to abrasion and impact, as
in the case of paving materials
d) Long-time tests: there are made with loads applied to the object under test for
a long period of time. They are used for materials such as concrete.
e) Fatigue test: these are made with fluctuating stresses repeated a large number
of times
Cont…………………….

Classification of Mechanical Tests
 With reference to the effect of the test on the specimen
a) Destructive tests: Under these test methods, the specimens are either
crushed or ruptured and made useless at the end of the tests. Examples:
Ultimate strength of steel & Compressive strength of concrete
b) Non-destructive tests: These are usually used to test the strength of
members of existing structures without affecting their performance.
Example: hammer test
Cont……………………

 Stress-Strain Properties in Simple Tension Test
 In standard conventional tension test, specimen is subjected to
a gradually increasing axial tensile force ‘P’ by means of
testing machine.
 At various increments of load ,the change in length ∆L of the
specimen is measured.
 It is assumed that the stress is uniformly distributed for all
points on each x-section. This stress is computed as follow;
Cont…………………….

 The uniform stress will produce a uniform elongation ∆L. The
elongation per unit length is strain & expressed as:
 with the values of strain & stress known for various tensile loads ,a
diagram showing the relation between stress & strain ,called stress-
strain diagram can be plotted
Cont………………………

Cont………………………..

 Properties in the elastic range
 The parameters which are used to describe the mechanical
properties of a material in the elastic range are:
 proportional limit,
 elastic limit,
 modulus of elasticity, stiffness etc.
 Proportional Limit: is the greatest stress which a material is capable
of withstanding without deviation from the law of proportionality of
stress to strain. (point a of fig 1)
Cont………………………..

 Elastic Limit: is the greatest stress which a material is capable of
withstanding without a permanent deformation remaining up on the
release of stress. (point b of fig 1)
 Yield Point: is the stress at which there occurs a considerable
increase in strain without an increase in stress. Only ductile
materials have both lower & upper yield points. (point c of fig 1)
Cont…………………………

 Modulus of Elasticity(young’s modulus)
 is the slope of the initial linear part of stress-strain diagram.
 The greater the modulus of elasticity, the smaller the elastic strain resulting from
the application of a given values.
 Methods of determining modulus of elasticity, E.
 For materials with linear stress – strain portion
E= ∆ σt ∕ ∆ ε
Cont……………………

 For materials with non-linear stress-strain curves
 The slope of the stress- strain curve varies and the modulus of
elasticity cannot be readily determined. The following three
methods are employed to define E:
 Initial-Tangent modulus: The slope of the stress –strain curve at the
origin which has a value of E1 =tanф1
Instructor: Lili M.
Cont………………………..

 Secant modulus : the slope of the line joining the origin and the
selected point on the stress-strain curve with the value of E 2
=tanф2
Cont……………………..

 Tangent modulus: The slope of the tangent to the stress –strain
curve at the selected point with the value of E 3 =tanф3
Cont………………………..

 Stiffness
 Is the measure of the ability of material to resist
deformation.
 The higher the modulus of elasticity, the stiffer the
material.
 A material has a higher stiffness value when its
deformation in the elastic range is relatively small.
 Comparing steel alloys with E=210Gpa and
aluminium alloys with E=70Gpa,the steel alloys are
about three times as stiff as the aluminium alloys i.e
steel alloys will deform about one-third as much as
aluminium alloys for the same stress.
Cont……………………….

 Poisson’s Ratio
 Is the ratio of the unit deformations or strains in transverse direction
to the longitudinal direction within proportional limit.
µ= ε’∕ ε
where ε’ = transverse strain,
ε =longitudinal strain
 Poisson’s ratio is a measure of the stiffness of the material in the
direction at right angle to applied load.
Cont………………………….

 Poisson’s Ratio….
Cont………………………….

 The parameters which are used to describe the mechanical
properties for the plastic range are; ultimate strength, ductility and
toughness.
 Ultimate Strength:-is the maximum strength a material can
possibly resist before failure.
Properties for the plastic range

 Properties for the plastic range
Cont………………………

 Ductility:-
 represents its ability to deform in the plastic range (varies from 5 to
over 100 cm's).
 Ductile materials show relatively higher plastic deformation, i.e
they are capable of being drawn-out ,before rupture occurs.
 Ductility is measured by the percentage elongation or percentage
reduction in area.
Cont………………………..

 Toughness
 Is the ability of material to absorb energy in the plastic range.
 A material with high toughness can absorb high values of strain
energy in the plastic range.
Cont………………………..

Thank you
1/21/2024
End

Material -1.ppt

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