THE UNIVERSITY OF THE WEST INDIESFACULTY OF ENGINEERING

CVNG 1005 - COSTRUCTION MATERIALS

INTRODUCTION TO CONSTRUCTION MATERIALS

Lecture aims:

Provide a definition of ‘matter’ and a basic knowledge of some fundamental physical and chemical properties of materials.

Explore and list the range of material types used in the construction industry.

Provide a basic knowledge of some environmental aspects of current construction materials

The Oxford English Dictionary defines matter as:

“..a physical substance in general as distinct from mind and spirit”

and;

“..that which has mass and occupies space”

Matter can be classified into three groups:

Elements Compounds Mixtures

An

element……………………………………………………………………………………..

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A compound is a substance composed of two or more elements chemically combined in a definite proportion. They can be broken down into their constituent elements only by chemical change.

A mixture is a combination of two or more substances that retain their individual properties. They are held together by physical rather than chemical mechanisms and include soil, seawater and rock. Examples of a mixture include solutions and suspensions. A solution is a mixture that is uniform throughout (homogenous) and contains the very smallest particles (ions, atoms or molecules) of two or more substances

Figure 1 - Elements, compounds & mixtures: relationships

Extend figure 1 to show that the elements are the building blocks of all materials:

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………States of matter

Under most conditions, matter can exist as a solid, liquid or gas, each of which has certain distinct characteristics. Under certain extreme conditions of heat matter can exist in fourth state, termed plasma. Such conditions, naturally found in the sun’s interior, can be created artificially.

On a fundamental level it is believed that all matter consists of tiny particles called atoms. Atoms are made up of 3 types of particles electrons , protons  and neutrons .  These particles have different properties.  Electrons are tiny, very light particles that have a

Matter

CompoundsElements Mixtures

One element mixed with one or

more other elements

One compound mixed with one or

more other compounds

One or more elements mixed

with one or more compounds

(Homogeneous) (Homogeneous) (Can be homogeneous or heterogeneous)

Types of mixtures

metals Non-metals Covalent Ionic

negative electrical charge (-). Protons are much larger and heavier than electrons and have the opposite charge, protons have a positive charge (+).  Neutrons are large and heavy like protons, however neutrons have no electrical charge.  Each atom is made up of a combination of these particles, evidence for which comes from consideration of the reactions and properties of solids, liquids and gases. The movement of particles is explained by the kinetic theory of matter

The basic ideas of the kinetic theory are

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b)

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According to this theory, the temperature of a body is a measure of the average kinetic energy of it particles. This theory can also be used to explain the differences between the different states (or phases) of matter

SolidsMolecules in solids maintain fixed positions, giving the material a definite shape and a fixed volume. The tightly packed molecules (a molecule is defined as the smallest unit of substance that retains the properties of that substance) are held together by bonding (usually covalent or ionic).

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The temperature at which a solid becomes a liquid is called its melting point. At this point, the random motion, or vibration, of the molecules, which is increased by heat, causes them to become excited and break loose the bonds that keep them in place. The particles have low kinetic energy and although they vibrate around their fixed positions they cannot move from one place to another (Figure 2).

Figure 2 - movement of particles in the solid state

LiquidA liquid has a definite volume but no definite shape (i.e. it will usually assume the shape of the container in which it is held). It is a state of matter in which the molecules are loosely bound by intermolecular forces and are slightly further apart than in a solid. They have a higher kinetic energy and can move freely (Figure 3). The temperature at which a liquid becomes a solid is its freezing point, and the temperature at which it becomes a gas is its boiling point (Figure 4).

According to this theory, the temperature of a body is a measure of the average kinetic energy of it particles. This theory can also be used to explain the differences between the different states (or phases) of matter

SolidsMolecules in solids maintain fixed positions, giving the material a definite shape and a fixed volume. The tightly packed molecules (a molecule is defined as the smallest unit of

substance that retains the properties of that substance) are held together by bonding (usually covalent or ionic).

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The temperature at which a solid becomes a liquid is called its melting point. At this point, the random motion, or vibration, of the molecules, which is increased by heat, causes them to become excited and break loose the bonds that keep them in place. The particles have low kinetic energy and although they vibrate around their fixed positions they cannot move from one place to another (Figure 2).

Figure 2 - movement of particles in the solid state

LiquidA liquid has a definite volume but no definite shape (i.e. it will usually assume the shape of the container in which it is held). It is a state of matter in which the molecules are loosely bound by intermolecular forces and are slightly further apart than in a solid. They have a higher kinetic energy and can move freely (Figure 3). The temperature at which a liquid becomes a solid is its freezing point, and the temperature at which it becomes a gas is its boiling point (Figure 4).

Figure 3 - movement of particles in the liquid state.

GasesGases have no fixed shape or volume. The force of attraction between the molecules of a gas is small because of the relatively large distances between the molecules (Figure 4). As a result the molecules are always in motion and will continually collide with each other or the walls of the container that they are in, creating what is known as gas pressure. The volume of a gas is affected by changes in temperature and pressure. The temperature at which a liquid becomes a gas is called its boiling point; the boiling point also depends on the pressure exerted. The temperature at which a gas becomes a liquid is called its condensation point.

BOYLES LAW…………………………………………………………………………………………………………………..………………………………………………………………………………………………………………………………………………………………………………

Figure 4 - movement of particles in the gas state

PlasmaPlasma is a form of matter that initially exists as a gas and then becomes ionized (i.e. an atom which carry a positive or negative charge) and consists of free moving ions and electrons. It exhibits different properties from any of the other states of matter.

Figure 5 - Changes between material phases

A change of state directly from a solid to a gas or a gas to a solid (i.e. without going through a liquid phase is termed sublimation.

Physical properties of matter

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…………. Some properties are dependent upon the amount of substance that is being

observed such as volume and mass. Those that are not dependent include; density,

colour, hardness, strength, taste, odour, boiling point, melting point, thermal conductivity

and elasticity.

E.g.

Table 1 - Freezing and boiling points of common substances

Substance Freezing point (oC) Boiling point (oC)Iron 1535 2750

Mercury -39 357Nitrogen -209 -196Oxygen -218 -183Water 0 100

Table 2 - Densities of common substance at 20oC

SubstanceDensity (kg/m3)

AluminumCopper

IronGoldSilverLead

ChloroformEthyl Alcohol

MercuryWater

HeliumHydrogenOxygenNitrogen

270089607870193201050011350

1490790

135501000

0.16630.08371.3311.165

Materials in the Construction Industry

It could be argued that ‘Construction’, whether building or civil engineering, is primarily

involved with the movement and assembly of materials. The following shows the main

material ‘types’ used in construction along with some of their applications

MetalsAlthough it is predominantly steel, in all its forms, that is the most widely used metal in

construction, other metals such as copper, lead, aluminum and zinc also used. Uses

include: Structural steelwork, scaffolding, formwork, cladding, concrete reinforcing bar,

wall ties, fasteners, plant & tools, sheet piling, trench support, pipes, roofing,

wiring/electrical components and architectural furniture.

Wood

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Soils/rock

Generally refers to quarried, dredged or excavated material and includes sands and

gravels, crushed rock, topsoil, uses include: fill material, stone cladding, roof tiles,

landscaping, building blocks, bricks, blocks, sea defence, embankments, sub-base

material, aggregates and cement production.

Cementitious/concrete products

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Concrete is produced when mixed with fine and coarse aggregate. Uses include:

Foundations, floors, roads, pre-cast (e.g. lintels etc), piles, blockwork, screeds, structural

reinforced concrete, grouting and soil stabilization, dams, reservoirs, sea defence,

retaining walls and mortars.

Bituminous materials

The title is generally taken to include natural asphalt, coal tar, and bitumen from crude

petroleum (Petroleum bitumen). They can generally be described as non-crystalline

solid/viscous material containing complex hydrocarbons. It softens when heated, has

adhesive properties and softens when heated. It can be natural or derived. Road

construction (asphalt), roofing, waterproofing applications, paints and adhesives.

Polymers

Polymers are compounds with very large molecules made up of repeating molecular units

(long chains). Monomers are small molecules from which polymers are made. Polymers

can be natural such as cellulose, starch and rubber or artificial such as plastics and

nylons. Uses include: sealants, concrete additives, adhesives, pipework, sheeting, foams,

cable insulation, composite materials (carbon fibre), fiberglass, geotextiles, window

frames, Expansion joints and surface coatings.

Type Materialsincluded

Annual Consumption (t)

MineralsCrushed rock and gravel 254,000,000

Metals Steel, copper, brass, aluminium and other metal alloys

3,350,000

Plastics PVC, polyethylene, polystyrene, polyurethane

>550,000

Paints Paints, emulsions and varnishes 410,000Timber products Plywood and particleboard 3,850,000m3

Table 3 Quantities of materials used in UK construction (CIRIA, SP116, 1995)Environmental Considerations

Environmental impactsThe construction industry arguably has a number of negative impacts on the environment with construction materials forming a significant part of those impacts.

Some of these impacts can be listed as follows:

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Manufacturing produces pollution and waste, including toxic waste (e.g. cement production is a significant contributor to national carbon dioxide, CO2, emissions)

Some materials, once installed, can release toxic gases which can affect occupant health (i.e. sick building syndrome)

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Disposal of materials can waste materials, which could be re-used, requires landfill space and can degrade groundwater.

This has resulted in legislation and initiatives (e.g. Environ mental Protection Act, 1990) and the increased use of ‘green’ construction materials.

Generally, ‘green’ materials are selected for their low consumption of scarce raw materials, low pollution associated with its production, delivery, use and disposal, low maintenance, long life and potential for recycling and re-use. To determine whether a material is ‘green’, a technique called whole life cycle assessment is used. In this, environmental impact of the material is considered in terms of :

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In the United Kingdom, the government has adopted the concept of sustainable development at both a national and local level. Sustainable development can be defined as development, which aims to meet the needs of the present without compromising the needs of the future. Its broad aims are:

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The construction industry has been identified as playing an important part in such development by addressing “what it builds, where it builds and how it builds”. The subject of materials is highlighted as being of particular importance, particularly in the areas of waste disposal and consumption of new resources

Increased usage of recycled materials will result in a reduction in the use of primary materials and the production of less waste.

Examples of recyclable materials include:

Reclaimed bricks, china clay waste, crushed concrete for use as an aggregate in concrete, colliery spoil, demolition rubble, foundry sand, pulverized fuel ash (PFA), Blast furnace slag, timber, topsoil, railway ballast, sewage slag, rubber, roofing tiles, steel and other metals.

Further reading

Selected reading of CIRIA publications referred to in the text (available through the Construction Information Database accessible via the Learning Centres website)

TAYLOR, G.D. (2001) Materials in construction–an introduction. 3rd Ed. Harlow: Pearson Education Ltd. Ch. 1.