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CIV-E1010 Building Materials Technology (5 cr) (1/21) Lecture 1. Mechanical and non-mechanical properties of building materials Prepared by: Fahim Al-Neshawy, D.Sc. (Tech.) Aalto University School of Engineering Department of Civil Engineering A: P.O.Box 12100, FIN-00076 Aalto, Finland
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CIV-E1010 Building Materials Technology (5 cr) (1/21)

Lecture 1. Mechanical and non-mechanical properties of buildingmaterials

Prepared by:Fahim Al-Neshawy, D.Sc. (Tech.)Aalto University School of EngineeringDepartment of Civil EngineeringA: P.O.Box 12100, FIN-00076 Aalto, Finland

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Table of ContentsLecture 1. Mechanical and non-mechanical properties of building materials ...................................... 1

1.1 History of building materials ........................................................................................................... 3

1.2 Introduction to building materials .................................................................................................. 5

1.3 Fundamental Properties of Building Materials .............................................................................. 7

1.3.1 Parameters of state / structural characteristics .................................................................... 7

1.3.2 Physical properties ................................................................................................................. 10

1.3.3 Mechanical properties ........................................................................................................... 13

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1.1 History of building materials (1)

People have constructed buildings and other structures since prehistory, including bridges,amphitheatres, dams, roads and canals. Building materials in present use have a long history andsome of the structures built thousands of years ago are regarded as remarkable.

Table 1. Brief history of building materials (Error! Bookmark not defined.)

Time Period name Example Building Materials

32000 –12000 BC.

Paleolithic(old stone age)

A Paleolithic settlement.

· Temporary homes in caves or tents madefrom branches and animal skins.

12000 –8000 BC

Mesolithic(middle stoneage).

Temporary shelter fromperishable materials

· TENT: wooden poles/animal bones asframework and leaves to form the tent

· HUT: broad leaves intertwined ascovering, composite building materialswere used (clay & wood)

8000 –3000 BC.

Neolithic(New Stone Age)

Villages of circular & laterrectangular huts, communal house

· Communal house: walls were made ofvarious materials, such as clay, wattle &daub, tree bark & thatch

· Stone structures: dolmen, granaries,temples and cromlech

2900 –2350 BC

Mesopotamianperiod

Babylonian city

· Construction examples are:Tower of Babel, city of Babylon

· Material used:Chaldea – man-made clay, plain & glazedbricks, bitumen & pitch (for cementing),calcerous earth (mortar)Assyria – stone, brick (extensively used),alabaster & limestone (for facing)Persia – hard & colored limestone,timber

1 Fernandez, Rino. (2012). Brief history of building materials. Power Point presentation available at:http://www.slideshare.net/ulrick04/bt-history-of-building-materials

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3100 –332 BC Egyptian period

Temple of Horus at Edfu, Egypt

· Natural products – timber, stone, brick,clay

· Masonry materials – limestone,sandstone, alabaster, basalt, porphyry,granite

· Timber used – Acacia (boats), Date Palm(roofing), Sycamore (mummy case)

900 BC untilthe 1stcentury AD

Greek period

The Parthenon temple

· Building materials: Marble, stones asLimestone, mud brick, masonry blocksetc.

100 BC – 1400 AD Roman period

The Colosseum in Rome, Italy

· Building material: pozzolanic concrete,Stone like Marble used to decoratesurfaces, lime and sandstone, basalticlava or granites, different types of wood,terracotta and ceramics, bricks, metalssuch as iron and tin.

Originatingin 12th-centuryFrance andlasting intothe 16thcentury

Gothic period

Reims Cathedral, France

· The most fundamental element of theGothic style of architecture is the pointedarch

· Building materials: red bricks, glazedbricks and white lime plaster

Early 14th

and early17th

centuries indifferentregions ofEurope

Renaissanceperiod

Château d'Amboise on the riverLoire, France

· Orderly arrangements of columns,pilasters and lintels, as well as the use ofsemicircular arches, hemisphericaldomes, niches and aedicules replaced themore complex proportional systems andirregular profiles of medieval buildings.

· Marble is used to construct mostly civicbuildings and in some cases religious (2)

2 Dimitris Havlidis, (2015). What were medieval houses and structures built from? Available online at:http://www.lostkingdom.net/medieval-architecture-building-materials/

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The mid-18th

century andthe end ofthe 19th

century

Period ofindustrialrevolution

The Royal Albert bridge, England

· Building material: Concrete, Steel, Glass.· Concrete development:

- 1756 - British Engineer, John Smeatonmade the first modern concrete(hydraulic cement) by adding pebbles as a course aggregate &mixing powered brick into the cement

- 1824 - Joseph Aspdin inventedPortland Cement

- 1849 - Joseph Monier inventedReinforced Concrete, and patented in1867

20th and 21th

centuryModernarchitecture

Arena-zagreb, Croatia

Burj Khalifa, Dubai

· Innovative building material: Theadvanced building materials market(including green building materials) isconstituted by innovative new producttypes with particular strength, thermaland/or low maintenance properties.

· Examples of the advanced materials are:- Translucent concrete- Solar panel roofing tiles- Electrified wood- Unfired clay bricks- Carbon fiber- Self-repairing (healing) concrete- Liquid granite- Bendable concrete

1.2 Introduction to building materials

· Building material is any material which is used for construction purposes in the form of solid,semi-solid or liquid, processed or unprocessed (raw material). Basically the building materialsare identified into two types-the natural and synthetic products.

o Many naturally occurring substances, such as clay, rocks, sand, and wood, even twigsand leaves, have been used to construct buildings.

o Apart from naturally occurring materials, many man-made products are in use, somemore and some less synthetic, such as fired bricks and clay blocks, ceramics, cement,composites, concrete, thermal and sound insulation, glass, metal, plastics, polymers,etc.

· Responsibilities of material engineer (3):o A material engineer must be familiar with a wide range of materials used in a wide

range of structureso Responsibilities of a material engineer include:

3 http://www.aboutcivil.org/factors-affecting-selection-of-construction-material.html

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§ Selection of materials for different structural components (roofs, walls, floors,sub-structures, etc.)

§ Specification of materials§ Quality control of materials

· There are five primary areas that must be evaluated in selecting appropriate materials andassemblies, as shown in Figure 1. (4)

o Material compatibility with climatic (environment) and cultural conditionso Material compatibility with aesthetic conditionso Construction consideration such as the applicability of material to occupancy and size

of building, including durability, structural, and fire protection requirementso Economic factors such as the environmental impact of obtaining raw materials,

processing and fabricating building materials, transportation impact, Initial andongoing costs, and recycling issues

o Mechanical and non-mechanical properties of the building materials

Figure 1. Overview of the building material selection criteria

4 Material Use: Specifying efficient use of materials and considering their impact from manufacture to disposal.http://www.level.org.nz/material-use/choosing-materials/

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1.3 Fundamental Properties of Building Materials (5)

A building material's property is an intensive, often quantitative, property of the material.Quantitative properties may be used as a metric by which the benefits of one material versus anothercan be assessed, thereby helping in materials selection. The fundamental properties of buildingmaterials include:

1. Parameters of state / structural characteristics2. Physical (non-mechanical) properties3. Mechanical properties

1.3.1 Parameters of state / structural characteristics (6)

1.3.1.1 Density and unit weightDensity (r), the volumetric mass density, is the mass of a unit volume of homogeneous material, AKApractical density. The density at all points of a homogeneous object equals its total mass divided byits total volume. The mass is normally measured with a scale or balance; the volume may bemeasured directly (from the geometry of the object) or by the displacement of a fluid.

Figure 2. Density of materials.

Density of some building materials is as follows:

Table 2. Examples of the density and bulk density of some building materials.

Building materials Practical Density [kg/m3] Bulk Density [kg/m3]Brick 2500 – 2800 1600 - 1800Granite 2600 – 2900 2500 - 2700Cement 2900 – 3100Wood 1500 – 1600 Pine wood: 500 - 600Steel 7800 – 7900 7850Concrete 2400

5 S. K. Duggal, (2008) Building Materials – chapter 1: 4. Principal Properties of Building Materials.6 Bjørn Berge (2009). The ecology of building materials – Chapter 4 The chemical and physical properties of buildingmaterials.

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Bulk Density (rb): is a property of powders, granules, and other "divided" solids, especially used inreference to mineral components (soil, gravel). It is defined as the mass of many particles of thematerial divided by the total volume they occupy. The total volume includes particle volume, inter-particle void volume, and internal pore volume. The bulk volume of a material—inclusive of the voidfraction—is often obtained by a simple measurement (e.g. with a calibrated measuring cup) orgeometrically from known dimensions.

Figure 3. Bulk density.

For most materials, bulk density is less than density but for liquids and materials like glass and densestone materials, these parameters are practically the same. Properties like strength and heatconductivity are greatly affected by their bulk density.

Density Index (r0): The density index indicates the degree to which the volume of a material is filledwith solid matter. For almost all building materials the density index is less than 1.0 because there areno absolutely dense bodies in nature.

= = (1)

Specific Weight (g), also known as (the unit weight). The specific weight is the weight per unit volumeof material. Specific weight can be used in civil engineering to determine the weight of a structuredesigned to carry certain loads while remaining intact (unbroken) and remaining within limitsregarding deformation. It is also used in fluid dynamics as a property of the fluid (e.g., the specificweight of water on Earth is 9.80 kN/m3 at 4°C).

(2)

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Specific Gravity (Gs) of solid particles of a material is the ratio of weight/mass of a given volume ofsolids to the weight/mass of an equal volume of water at 4°C

(3)

1.3.1.2 Porosity• Porosity or void fraction is a measure of the void (i.e., "empty") spaces in a material, and is a

fraction of the volume of voids over the total volume.

• Effective porosity (also called open porosity): Refers to the fraction of the total volume inwhich fluid flow is effectively taking place.

• Ineffective porosity (also called closed porosity): Refers to the fraction of the total volume influids or gases are present but in which fluid flow cannot effectively take place and includesthe closed pores.

Figure 4. Porosity of materials

Void Ratio (e)

Void ratio is defined as the ratio of volume of voids (Vv) to the volume of solids (Vs). There are twomethods for measuring voids:

· The direct method: consists in determining the volume of liquid, generally water, which isrequired to fill the voids in a given quantity of material

· The indirect method: the solid volume of a known quantity of aggregate is obtained bypouring the material into a calibrated tank partially filled with water; the difference betweenthe apparent volume of material and the volume of water displaced equals the voids.

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Figure 5. Void ratio and porosity.

1.3.2 Physical properties (7)

1.3.2.1 Hydro-physical properties· Hygroscopicity: is the capacity of a product (e.g. cargo, packaging material) to react to the

moisture content of the air by absorbing or releasing water vapor.· Water absorption (Ww): The amount of water absorbed by a material when immersed in

water for a period of time. Materials with coefficient of softening less than 0.8 should not berecommended in the situations permanently exposed to the action of moisture

Figure 6. Water absorption test

· Moisture: Water content or moisture content is the quantity of water contained in a material,such as soil, rock, ceramics, or wood

· Water permeability: The rate of water vapor flow in cubic meter per day through a crosssection of 1 square meter under a unit hydraulic gradient, at the prevailing temperature.

7 S. K. Duggal, (2008) Building Materials – chapter 1: Materials Engineering Concepts, Section 1.3 Non-MechanicalProperties.

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1.3.2.2 Thermal -technical properties (8)

Thermal Conductivity (k): (sometimes “l”) is the material ability to conduct heat. Each material has acharacteristic rate at which heat will flow through it. The faster heat flows through a material, themore conductive it is.

Figure 7. Thermal conductivity.

=∗∗ Δ (4)

· k = the thermal conductivity of the material (W/mK).· q = the resultant heat flow (Watts)· A = the surface area through which the heat flows (m²)· ∆T = the temperature difference between the warm and cold sides of the material (K)· L = the thickness / length of the material (m)

8 Building Energy Fundamentals - Thermal Properties of Materials. Available at:http://sustainabilityworkshop.autodesk.com/buildings/thermal-properties-materials

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Thermal Expansion: (9)

· Practically all materials expand as temperature increases andcontract as temperature falls. The amount of expansion perunit length due to one unit of temperature (DT) increase is amaterial constant and is expressed as the coefficient ofthermal expansion.

· The coefficient of thermal expansion is very important in thedesign of structures. Generally, structures are composed ofmany materials that are bound together. If the coefficients ofthermal expansion are different, the materials will strain atdifferent rates. The material with the lesser expansion willrestrict the straining of other materials. This constrainingeffect will cause stresses in the materials that can leaddirectly to fracture.

· Stresses can also be developed as a result of a thermalgradient in the structure. As the temperature outside thestructure changes and the temperature inside remainsconstant, a thermal gradient develops. When the structure isrestrained from straining, stress develops in the material.

Fire resistance: A fire-resistance rating typically means the duration for which a passive fireprotection system can withstand a standard fire resistance test.

Thermal diffusivity: The thermal diffusivity is a measure of the transient heat flow through a material.

Specific heat: The specific heat is a measure of the amount of energy required to change thetemperature of a given mass of material.

Melting point: The melting point is the temperature at which a material goes from the solid to theliquid state at one atmosphere.

1.3.2.3 Viscosity· Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or

tensile stress.· In everyday terms (and for fluids only), viscosity is "thickness" or "internal friction".· Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity.· Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of

fluid friction.· Plastic viscosity of concrete is critical for the concrete industry because it affects placement

and workability.

9 S. K. Duggal, (2008) Building Materials – chapter 1: Materials Engineering Concepts, Section 1.3 Non-MechanicalProperties

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1.3.3 Mechanical properties

1.3.3.1 StrengthStrength of materials is a subject which deals with the behaviour of solid objects subject to stressesand strains. When a solid body (assumed to be at rest) is acted upon by external forces (assumed tobe in equilibrium), the body is deformed and internal forces are developed in the body that balancethe external applied forces.

· In materials science, the strength of a material is its ability to withstand an applied loadwithout failure or plastic deformation.

· The field of strength of materials deals with forces and deformations that result from theiracting on a material.

Types of loadings:

· Transverse loading - Forces applied perpendicular to the longitudinal axis of a member.· Axial loading - The applied forces are collinear with the longitudinal axis of the member.· Torsional loading - Twisting action caused by a pair of externally applied equal and

oppositely directed force couples acting on parallel planes or by a single external coupleapplied to a member that has one end fixed against rotation.

Figure 8. Different types of loads.

· Depending upon the arrangement and direction of external loads, the stress produced in thebody may be:

o Direct stress (direct tensile stress or direct compressive stress)o Bending stress (bending tensile stress or bending compressive stress),o Shearing stress,o Torsional stress, oro A combination of the different stresses.

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Loading conditions:

The two basic types of loads are static and dynamic. Each type affects the material differently, andfrequently the interactions between the load types are important. Civil engineers encounter bothwhen designing a structure.

1. Static loading implies a sustained loading of the structure over a period of time. Generally,static loads are slowly applied such that no shock or vibration is generated in the structure. Incivil engineering, much of the load the materials must carry is due to the weight of thestructure and equipment in the structure.

2. Dynamic loads: Loads that generate a shock or vibration in the structure are dynamic loads.Dynamic loads can be classified, shown in Figure 9, as:

a. Periodic load, such as a harmonic or sinusoidal load, repeats itself with time. Forexample, rotating equipment in a building can produce a vibratory load.

b. Random load, the load pattern never repeats, such as that produced by earthquakesa. Transient load is an impulse load that is applied over a short time interval, after which

the vibrations decay until the system returns to a rest condition. For example, bridgesmust be designed to withstand the transient loads of trucks.

Figure 9. Types of dynamic loads: (a) periodic, (b) random, and (c) transient.

1.3.3.2 Stress–strain relationsWhen a solid material is not experiencing any external forces, all the molecules that make up thematerial are vibrating about their equilibrium positions. This is the lowest-energy configuration forthe molecules, and if they are moved away from their equilibrium positions the molecules wouldattempt to get back to their equilibrium positions. Technically, stress is a measurement of theseintermolecular forces. If the material is not under acceleration, then the intermolecular forces shouldbe balanced by the external forces acting on the material. Therefore, we can get an indication ofstress by measuring the external forces acting on the object. The stress (s) on an object is given bythe external force on the object divided by the cross-sectional area of the sample of a material.

When an object is under stress, it undergoes deformation. Strain is a measurement that gives thechange in length of an object divided by the original length. Strain is usually given the symbol (e). If wesubject a sample of material to different levels of stress, measure corresponding strains and thenproduce a graph of stress vs. strain, then we obtain what is called a stress-strain curve, which ischaracteristic curve for a given material. The graph below shows the stress-strain curve for a typicalductile material such as steel:

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Figure 10. Stress – strain curve for a ductile material (10).

What is yield strength?

When the stress on a material is slowly increased, you can see that the strain increases in proportionin the beginning. If the force causing stress on the material is removed, then the material wouldreturn to its original shape. When a material is able to do this, we say that the material is elastic (thinkof a rubber band). If the stress on the material keeps increasing, then the material would eventuallyreach a point when the material becomes so deformed that, even when the deforming forces areremoved, the material is unable to return to its original shape. The stress at which a material stopsbehaving elastically is called the yield strength. When the material is unable to return to its originalshape, we say that the material is plastic.

What is ultimate strength?

Suppose you keep increasing the forces on the material beyond yield strength. The material keepsdeforming, and eventually the forces between the molecules become unable to counter the externalforces and the material breaks. The maximum stress that the material can handle before breaking iscalled tensile strength or ultimate strength.

When a body of uniform cross section is subjected to a tensile force it elongates in the direction offorce at the same time its lateral dimensions are reduced. Figure 11 shows plot of tensile stress andthe corresponding strains for some of the materials.

10 http://pediaa.com/difference-between-yield-strength-and-tensile-strength/

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Figure 11. Typical uniaxial stress–strain diagrams for some building materials.

Consider a bar of cross sectional area (A) being subjectedto equal and opposite forces (F) pulling at the ends so thebar is under tension. The material is experiencing a stressdefined to be the ratio of the force to the cross sectionalarea of the bar:

( ) = The SI unit of stress is (N/m2), which is called thepascal.(Pa = 1 N/m2)Strain is defined as "deformation of a solid due to stress"and can be expressed as:

( ) =∆

Figure 12. Stress–strain curve showingtypical yield behavior for nonferrousalloys. Stress (σ) is shown as a functionof strain (ϵ)

1.3.3.3 Elastic behaviourThe elasticity is the property of a substance to deform with external forces and return to its originalshape when the stress is removed, as shown in Figure 13. The deformation fully capable of restorationis called elastic deformation. Within the range of the elastic deformation, the ratio of the stress (r) tothe strain (e) is a constant (E) which is known as modulus of elasticity or “Young’s modulus”, namely,E= r/e. The elastic modulus is a measure of the ability to resist deformation. The bigger E is, the moredifficultly the material deforms. The elastic modulus of low-carbon steel is E=2.1x105 MPa; and theelastic modulus of concrete is a variable value, with its strength grades increasing from C15 to C60and its elastic modulus E increasing from 1.55 x 104 MPa to 3.65 x 104 MPa.

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Figure 13. Illustration of the elastic deformation (Elastic means reversible)11

In the axial tension test, as the material is elongated, there is a reduction of the cross section in thelateral direction. In the axial compression test, the opposite is true. The ratio of the lateral strain (el),to the axial strain (ea), is Poisson’s ratio (V):(9)

( ) =−

Since the axial and lateral strains will always have different signs, the negative sign is used to makethe ratio positive. Poisson’s ratio has a theoretical range of 0.0 to 0.5, where 0.0 is for a compressiblematerial in which the axial and lateral directions are not affected by each other. The 0.5 value is for amaterial that does not change its volume when the load is applied. Most solids have Poisson’s ratiosbetween 0.10 and 0.45.

Figure 14. Normal stresses applied on a cubical element.

If a homogeneous, isotropic cubical element with linear elastic response is subjected to normalstresses (sx, sy, sz) in the three orthogonal directions, the normal strains(ex, ey, ez) can be computedby the generalized Hooke’s law (as shown in Figure 14).

Table 3 shows typical modulus of elasticity and Poisson’s ratio values for some materials at roomtemperature.

Table 3. Typical Modulus of elasticity and Poisson’s Ratio Values (Room Temperature)

MaterialModulus of Elasticity

[GPa] Poisson’s RatioAluminum 69–75 0.35Brick 10–17 0.23–0.42Concrete 14–40 0.11–0.23Epoxy 3–140 0.35–0.45Glass 62–70 0.27Limestone 58 0.2–0.5Steel 200 0.29Wood 6–15 0.29–0.47

11 Nauras Saiyed, (2012). Building materials & construction. Unit -1: Mechanical Properties of Building Materials. Availableonline at: http://www.authorstream.com/Presentation/nauras-1480649-mechanical-properties-building-materials/

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Note that some materials have a range of modulus values rather than a distinct value. Several factorsaffect the modulus, such as for example curing level and proportions of components of concrete orthe direction of loading relative to the grain of wood.

1.3.3.4 Elastoplastic behaviourThe plasticity describes the deformation of a material undergoing non-reversible changes of shape inresponse to external forces. This non-reversible deformation is called plastic deformation.

Figure 15. Illustration of the plastic deformation (Plastic means permanent)12

Some materials exhibit strain softening, in which plastic deformation causes weakening of thematerial. Portland cement concrete is a good example of such a material. In this case, plasticdeformation causes micro cracks at the interface between aggregate and cement paste.

Materials that do not undergo plastic deformation prior to failure, such as concrete, are said to bebrittle, whereas materials that display appreciable plastic deformation, such as mild steel, are ductile.Generally, ductile materials are preferred for construction. When a brittle material fails, the structurecan collapse in a catastrophic manner. On the other hand, overloading a ductile material will result indistortions of the structure, but the structure will not necessarily collapse. Thus, the ductile materialprovides the designer with a margin of safety.

1.3.3.5 Viscoelastic behaviorViscosity is a measure of a fluid’s resistance to flow. Viscoelasticity is the property of materials thatexhibit both viscous and elastic characteristics when undergoing deformation. Typical viscoelasticmaterials used in construction applications are asphalt and plastics. Viscoelastic materials have adelayed response to load application. For example, Figure 16(a) shows a sinusoidal axial load appliedon a viscoelastic material, such as asphalt concrete, versus time. Figure 16(b) shows the resultingdeformation versus time, where the deformation lags the load; i.e., the maximum deformation of thesample occurs after the maximum load is applied. The amount of time delayed of the deformationdepends on the material characteristics and the temperature.

12 Nauras Saiyed, (2012). Building materials & construction. Unit -1: Mechanical Properties of Building Materials. Availableonline at: http://www.authorstream.com/Presentation/nauras-1480649-mechanical-properties-building-materials/

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Figure 16. Load-deformation response of a viscoelastic.

Some of the properties of viscoelastic materials are their ability to:

· creep,· recover,· undergo stress relaxation· absorb energy.

Figure 17. Behavior of time-dependent materials: (a) creep and (b) relaxation.

1.3.3.6 Temperature and time effects on the mechanical propertiesThe mechanical behaviour of all materials is affected by temperature. Some materials, however, aremore susceptible to temperature than others:

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· Viscoelastic materials, such as plastics and asphalt, are greatly affected by temperature, evenif the temperature is changed by only a few degrees.

· Metals or concrete, are less affected by temperatures, especially when they are near ambienttemperature.

· Ferrous metals, including steel, demonstrate a change from ductile to brittle behaviour as thetemperature drops below the transition temperature.

In addition to temperature, some materials, such as viscoelastic materials, are affected by the loadduration:

· The longer the load is applied, the larger is the amount of deformation or creep.· In fact, increasing the load duration and increasing the temperature cause similar material

responses.

1.3.3.7 DuctilityDuctility is defined as the “ability of material to undergo large deformations without rupture beforefailure”. Ductility in concrete is defined by the percentage of steel reinforcement with in it. Mild steelis an example of a ductile material that can be bent and twisted without rupture.

Significance of ductility:

• If ductile members are used to form a structure, the structure can undergo large deformationsbefore failure. This is beneficial to the users of the structures, as in case of overloading, if thestructure is to collapse, it will undergo large deformations before failure and thus provideswarning to the occupants. This gives a notice to the occupants and provides sufficient time fortaking preventive measures. This will reduce loss of life.

• Structures are subjected to unexpected overloads, load reversals, impact and structuralmovements due to foundation settlement and volume changes. These items are generallyignored in the analysis and design. If a structure is ductile than taken care by the presence ofsome ductility in the structure.

• The limit state design procedure assumes that all the critical sections in the structure willreach their maximum capacities at design load for the structure. For this to occur, all joints andsplices must be able to withstand forces and deformations corresponding to yielding of thereinforcement.

Comparison with brittle material

• Brittleness is a property of material that will fail suddenly without undergoing noticeabledeformations.

• Brittle structures do not give notice before failure and may collapse and the occupants maynot have time to take measures to prevent collapse.

• Concrete is an example of brittle material. To avoid failure of structure the structural engineermust take all provisions to increase the ductility of structure. The structural engineer should

Page 21: Lecture 1. Mechanical and non-mechanical properties of ... · Mechanical and non-mechanical properties of building materials ... Mechanical and non-mechanical properties of building

CIV-E1010 Building Materials Technology (5 cr) (21/21)

design a structure functioning as a ductile one. By suitably anchoring the reinforcement, theductility of a structure can be increased to a greater extent with little increase in cost.

Figure 18. Brittle and ductile force-deformation behavior (13)

13 P. C. Vasani, Ductility requirements for buildings. Online at: https://www.sefindia.org/?q=system/files/Ductility-1.pdf


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