CE 251 Lecture 1

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1

Dr Rajib ChowdhuryDepartment of Civil Engineering

IIT Roorkee

Module CE-251Building Materials,

Construction and Estimation

Lecture 1:

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CE-251 - 2Course details

C o n t a c t H o u r s / Week

Syllabus details

Relative weightage

3 lectures

1 tutorial

2/2 practical

Section 1 Building Materials.

Section 2 Estimation.

Section 3 Construction.

Coursework submission 15%

Practical report submission 15%

Mid-term examination 30%

Closed book Final examination 40%

Zero tolerance of late coursework submissionsZero tolerance of plagiarism zero module mark awarded.

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CE-251 - 3Texts

R e c o m m e n d e dtexts

Materials for Civil and Construction Engineers , Michael S Mamlouk,

John P Zaniewski, 3rd

EditionEngineering Materials, Surendra Singh, 4 th Edition

Engineering Material N. M. Murthy

Building Materials, S. K. Duggal, 3 rd Edition

Engineering Materials K. P. Roy Chowdhury, 7 th Edition

Civil Engineering Materials , Shan Somayaji, 2 nd Edition

Estimating and Costing, B. N. Dutta

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CE-251 - 4 Lecture Outline

! Functions of Building

! Role of Building Materials

! Physical & Mechanical Properties of Materials

! Clay material - Bricks

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CE-251 - 5 Functions of Building

The function of a building is to provide a desired spatial environment(controlled/uncontrolled), for given human activity.

" Controlled environment Temperature, Relative Humidity,etc.

" Uncontrolled environment The building, therefore, provides a safe and comfortable internal

environment against the existing external and unwanted internalconditions for given human activity.

The building must accomplish the same economically.

What are the functions of Building ?

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CE-251 - 6 Functions of Building

Safe against natural forces gravity, wind, rain and snowfall andearthquake etc. In addition, forces are also imposed due to humanactions.

Safety ?

Function is to withstand these loads Safely

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CE-251 - 7 Role of Materials

Loads are resisted by structural system. Structural system consists of members or elements connected at

junctions. The system is idealized to suit mathematical analysis and through the

analysis, forces on the members due to design loads are computed.

The size of the member for the material used must be able to resist thedesign forces.

" Material should have adequate axial, flexural and shearstrength. Strength/weight ratio may be important in some cases.

" Adequate stiffness is provided by modulus of elasticity of thematerial.

" Post elastic ductility.

" Resilience and damping properties.

Role of Material (safety)

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CE-251 - 8 Role of Materials

Thermal conductivity, diffusivity and coefficient of expansion. Transmission loss and transmissibility and sound absorption coefficient

of elements. Fire resistance of elements. Hydraulic diffusivity, permeability and vapour transfer coefficients.

Reflectivity

Role of Material (functional)

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CE-251 - 9Civil Engineering building materials

# C o m m o n c i v i l e n g i n e e r i n gmaterials:

$ steel$ mineral aggregates$ concrete$ masonry$ asphalt$ wood$ soil for geotechnical engineers

# Less common materials$ aluminum$ glass$ plastic$ Fiber-reinforced composites

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CE-251 - 10Civil Engineering building materials

Material Selection Considerations

# Economic factors# Mechanical properties# Non-mechanical properties# Production/construction# Aesthetic properties# Sustainable considerations

# Emphasis$ client

s needs$ facility

s function

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CE-251 - 11 Fundamental Properties of building materials

Physical Properties

Density - the mass of a unit volume of homogeneous material denoted by! =

M

V g/cm 3

Material Density

Brick 2.5 2.8Granite 2.6 2.9Portland Cement 2.9 3.1

Wood 1.5 1.6Steel 7.8 7.9

Bulk Density - is the mass of a unit volume of material in its natural state (with poresand voids) calculated as

! b = M

V kg/m 3

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Physical Properties

Material Bulk Density

Brick 1600 1800Granite 2500 2700Portland Cement 1450 1650Wood 500 600Steel 7850

Bulk Density - is the mass of a unit volume of material in its natural state (with pores andvoids) calculated as

! b = M

V kg/m 3

Density Index - It indicates the degree to which the volume of a material is filled withsolid matter. For almost all building materials this is less than 1.0 because there are noabsolutely dense bodies in nature.

! 0 =bulk density

density

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Physical PropertiesPorosity - is the degree to which volume of the material of the material is interspersed withpores. It is expressed as a ratio of the volume of pores to that of the specimen

n =V

v

V

Void Ratio - is defined as the ratio of volume of voids (Vv) to the volume of solids (Vs).

e =V

v

V s

Porosity is indicative of other major properties of material, such as bulk density, heat conductivity,durability, etc. Dense materials, which have low porosity, are used for constructions requiring highmechanical strength on other hand, walls of buildings are commonly built of materials, featuringconsiderable porosity.

Hygroscopicity - is the property of a material to absorb water vapour from air. It isinfluenced by air-temperature and relative humidity; pores - their types, number and size,and by the nature of substance involved.

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Physical Properties Water Absorption - denotes the ability of the material to absorb and retain water. It isexpressed as percentage in weight or of the volume of dry material

W w

=

M 1

! M

M " 100

W v

=

M 1

! M

V " 100

M1 = mass of saturated material (g). M = mass of dry material (g). V = volume of materialwith pores (mm 3).

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Mechanical Properties

Strength Hardness

Elasticity Plasticity Resilience

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Mechanical Properties

Strength is the ability of the material to resist failure under the action ofstresses caused by loads, the most common being compression, tension,bending and impact etc.

Hardness is the ability of a material to resist penetration by a harder

body. Hardness of metals and plastics is found by indentation of a steelball.

Elasticity is the ability of a material to restore its initial form anddimensions after the load is removed. Within the limits of elasticity ofsolid bodies, the deformation is proportional to the stress. Ratio of unit

stress to unit deformation is termed as modulus of elasticity. A large valueof it represents a material with very small deformation.

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Mechanical Properties Plasticity is the ability of a material to change its shape under load

without cracking and to retain this shape after the load is removed. Someof the examples of plastic materials are steel, copper and hot bitumen.

Resilience - is the ability of a material to absorb energy when it isdeformed elastically, and release that energy upon unloading. Themodulus of resilience is defined as the maximum energy stored in per unitvolume without creating a permanent distortion.

In Uni-axial loading

k r =!

y2

2 E

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Stress-Strain Relations

All solid materials deform under load# stress is like force (or load) with the size factored out so that we can

directly compare different sizes$ stress = force / area

s = F / A (psi, ksi, kPa, MPa, GPa)# strain is like deformation with the size factored out

$ strain = deformation / original lengthe =! L / L 0 (%, in/in, mm/mm)

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Typical Stress-Strain Diagrams

# s e is usually linear in the low stress range but transforms into non-linear

Glass andchalk

Steel Aluminumalloys

Concrete Softrubber

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# Instantaneous response to load# Returns to its original shape upon unloading

$ stretches bonds between atoms without rearranging them

Fundamental Properties of building materials

Elastic Behaviour

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Elastic Behaviour

# A linear material has a straight line stress-strain graph# An elastic material returns to its original shape

Linear elastic

Non-linear elastic

Non-linear inelastic

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# What if response is not linear?# How do we find the slope (Modulus of Elasticity)?

Strain

S t r

e s s

InitialTangentModulus

SecantModulus

ChordModulus

TangentModulus


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CE-251 - 23

S t

r e s s

Total Strain

ElasticStrainPlasticStrain

Force is applied resulting instress and strain

Strain

When force is removed,stress returns to zero.Path is parallel to the

initial slope of the curve.

Part of the strain is

recovered,

this iselastic behavior.

Part of the strain is

permanent , this isplastic behavior.

Elastic Limit

New elastic limit

Reloading will resume to the highestprevious stress level.

Elastic limit is

reset to the previoushighest stress level.

Response to furtherloading follows

original stress-strainbehavior


CE 251 Lecture 1

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