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Title: Mortar


1
Mortar
2
Introduction
  • Mortars are used in residential building in the
    following areas
  • as a render on masonry
  • as a bedding agent in brickwork
  • as a bedding agent for ceramic tiles
  • as a bedding agent for roof tiles
  • as a grout for ceramic tiles
  • as a topping mortar for concrete.

3
Learning outcomes
  • On completion of this unit, you should be able
    to
  • understand the role of lime and cement in the
    making of mortars
  • define mortar and describe the purpose of mortars
    in the building industry.

4
Lime
  • Lime for building purposes is obtained by burning
    (calcining) carbonate of lime (limestone). The
    material is burnt in a kiln for two to three and
    half days where moisture is driven off leaving
    rock or quicklime. There are several types of
    kiln ranging from a simple brick structure to an
    elaborate rotary type.
  • Lime is used as a component of mortars in
    brickwork, masonry and plastering, both in render
    and setting.

5
Rotary kiln (hydrated) lime
  • This is obtained by crushing rock lime in a
    machine and then spraying it with the exact
    amount of water required to slake it to a dry
    powder. This is then conveyed to a separator from
    which the lime powder is blown off into a storage
    bin, leaving the impurities behind. It is sold in
    25 kg paper bags, with 40 bags per tonne.
  • Properties of hydrated lime
  • Convenient package size for handling.
  • Does not deteriorate rapidly when stored.
  • Ready for immediate use in dry form.
  • Quantities may be accurately gauged.
  • It is pure lime.
  • Hydration is complete, therefore it will not be
    subject to blows in mortar due to later
    expansion of lime particles.
  • Modern additives are now used extensively by
    ready mix mortar manufacturers to produce a
    plastic or workable mix.

6
Portland cement
  • The process of manufacturing Portland cement was
    developed and patented in 1824 by an English
    bricklayer named Joseph Aspin, who named his
    product Portland cement because it resembled a
    yellowish building stone being quarried at
    Portland, England.
  • Modern industrial developments have led to a
    Portland cement which is no longer yellowish and
    therefore no longer resembles Portland stone, at
    least in colour, although the basic process of
    manufacture is still the same.

7
Process of manufacture
  • There are two methods used to manufacture
    Portland cement
  • the dry method
  • the wet method.
  • A description of the two methods follows.
  • Dry method
  • Limestone and clay or shale are finely ground.
  • The two ingredients are carefully proportioned
    and mixed.
  • The mixture is fired in a rotating cylindrical
    kiln. The burning temperature of the kiln is
    2600C 3000C. This causes a chemical change and
    produces a clinker consisting of vastly different
    chemical compounds to the raw material. (The term
    calcining does not apply to Portland cement
    manufacture.)
  • Gypsum is added to the resultant clinker and the
    mixture is finely ground again.
  • Wet method
  • This is similar to the dry method except that the
    initial grinding and mixing is done wet. Samples
    are tested in the laboratory and blending is
    carried out as required to produce the correct
    recipe. The mix is then injected into rotary
    kilns for burning. After burning the method is
    similar to the dry process.
  • Approximately 75 per cent of Portland cement
    produced in Australia is manufactured by the wet
    process.
  • Approximately 11/2 tonnes of limestone and 11/4
    tonnes of clay or shale are necessary to produce
    1 tonne of cement.

8
Uses
  • There are several types of Portland cement which
    are used as binding agents.
  • Type GP general purpose Portland cement
  • This cement is used in concrete for buildings or
    civil engineering structures such as dams,
    bridges, roads, tunnels, airport runways, wharves
    and jetties.
  • It is also used in precast or prestressed
    concrete products such as building components,
    both structural and architectural, bricks, blocks
    paving slabs and garden ornaments.
  • Type HE high early strength Portland cement
  • This material has special qualities due to extra
    fine grinding and/or variation in chemical
    composition by special selection and blending of
    raw materials. Setting time and ultimate strength
    are about the same as normal Portland cement. The
    cost is slightly increased.
  • Type LH low heat cement
  • This material liberates less heat during early
    setting and hardening than types 1 or 2. It is
    used therefore in mass concrete to control
    temperature rises in the concrete. It has
    somewhat better resistance to some forms of
    chemical attack than types 1 or 2 because of its
    chemical composition.

9
Aluminous cement
  • Composition and manufacture of this type of
    cement are considerably different to Portland
    cement. It is made from a mixture of limestone
    and bauxite (bauxite is the principal ore of
    aluminium). It is hydrated alumina.
  • Aluminous cement can be mixed with Portland
    cement to accelerate the hydration process and
    produce a fast rate of strength development.

10
Sand
11
Types of sand
  • Pit sandbeach or dune sand
  • This sand is suitable for use in mortar or
    concrete provided it is collected from above the
    salt water level or washed to remove any salt (eg
    Sydney or Botany sands).
  • Pit sand is generally white or cream. Grey sand
    is of inferior quality because it contains dirt.
    Bush pit sand, yellow or brown in colour, shrinks
    because of its 30 per cent or more clay content
    and is not recommended for use.
  • River sand
  • Usually this is good quality clean sand but it is
    often made up of particles that are smoother
    and/or coarser than good pit sand.
  • Crusher fines
  • This material is produced as a by-product in
    crushing rock. The particles are rough and
    splintery in shape (hungry) and therefore require
    more paste to produce a workable mix than natural
    sands.

12
Grading
  • A mixture of coarse and fine particles of sand
    used in mortar for general purposes should pass
    through a 5 mm mesh sieve. All particles passing
    this size are termed sand (and can be used for
    mortar) while those retained are termed coarse
    aggregate (and can be used for concrete). Clean
    sand available for building usually complies with
    this rule.

13
Examination
  • Clean sand will not leave a stain on white cloth
    or on the hands when rubbed together. Salt may
    sometimes be detected by tasting water after a
    small quantity of the sand has been immersed in
    it. A more reliable method is to use clean water
    to wash some sand in a small vessel and then add
    nitrate of silver. Clouding of the solution
    denotes the presence of salt.

14
Treatment of poor quality sand
Poor quality sand may be screened or sieved to
remove lumps, fine roots and stones. Dust, clay,
vegetable matter and salt may be removed by
washing the sand under running water in a trough
or shallow tank.
Substitutes for natural sand
  • Crushed sandstone is suitable for mortar when
    free from dust and clay.
  • Crushed furnace ashes or coke contains corrosive
    chemicals and is not suitable for use with steel
    reinforcement. It is, however, good for use in
    mortar exposed to low furnace heat such as in
    domestic coppers, incinerators and barbecues.

15
Mortar
  • Mortar may be defined as
  • a mixture of an aggregate or bulk material and a
    matrix or binding material.
  • Sand is the aggregate and lime and cement are the
    binding materials. These materials are combined
    to form different types of mortar mixtures in
    accordance with required strength.
  • Lime mortar
  • Lime mortar is a mixture of slaked rock lime or
    hydrated lime, clean sharp sand and clean water.
    This is a comparatively soft type of mortar of
    low strength.
  • Proportions are one part lime, 21/2 to 4 parts
    sand by volume and sufficient water to bring the
    mixture to a workable plastic state.

16
Mixing on the job
  • Using hydrated lime
  • Powdered lime may be used directly with measured
    quantities of sand or it may be soaked for 24
    hours in a large drum to fatten. The lime, sand
    and water may be mixed by hand on a clean hard
    surface or may be machine mixed.
  • Premixed lime mortar
  • This is widely sold by the truck load of 1.25 m3
    or in drums for small jobs. It is generally used
    for brickwork, when available, because of its
    convenience and the reduced costs in relation to
    mixing on the site.
  • Cement mortar
  • Cement mortar is a mixture Portland cement, clean
    sharp sand, and clean water and a small
    proportion of lime. This makes the strongest type
    of mortar.
  • Proportions are one part cement, 3 to 4 parts
    sand by volume 1/10 part lime together with
    sufficient water to make a workable plastic
    mixture.
  • Mixing is usually done by hand or by machine on
    the job.
  • Plasticising agents of many kinds, other than
    lime, are frequently used to make cement mortar
    more workable.
  • Cement mortar is best when used before the
    initial set takes place, normally about one hour
    after mixing. Mortar re-mixed after the initial
    set loses some strength and should not,
    therefore, be re-mixed for use.

17
Compo or lime-cement mortor
  • This medium strength mortar is a mixture of lime,
    cement, clean sharp sand and clean water. It sets
    harder than lime mortar but not as hard as cement
    mortar.
  • The standard mixture consists of either one part
    cement, one part rock or hydrated lime and 51/2
    to 6 parts sand, or one part cement, 2 parts rock
    or hydrated lime and 8 to 9 parts sand with
    sufficient water to make a plastic workable
    mixture. Quantities of materials should be
    carefully measured and either hand mixed or
    machine mixed.
  • Mortars of all types may be coloured red, brown,
    black, cream or green by adding mineral oxides in
    dry powder or liquid forms.
  • Grout, a thin or liquid mortar (usually cement)
    used for filling up joints. An excess of water
    makes the mortar weak. Where strength is
    required, additional cement is added to the
    grout. It is preferable to wet the work and allow
    the water to soak in before grouting.

18
  • Bush sand
  • In some areas (such as Sydney) bush sand and
    cement are mixed to produce a bricklaying mortar,
    in a ratio of 15. Bush sands contain a clayey
    loam which produces a very workable mix but which
    is susceptible to shrinkage. For low level
    residential work this does not pose any real
    problems.
  • Additives or admixtures
  • Proprietary admixtures are available for mortars
    and usually take the form of air in training
    agents and are used to make the mix more
    plastic and easier to use.
  • However, caution should be observed with the use
    of all admixtures as they are often used contrary
    to the manufacturers recommendations and their
    effects are often misunderstood by the users.

19
Summary
  • Portland cement and lime are generally used on
    building projects in bagged form and mixed on
    site. Their main use is on residential projects,
    including
  • mortar for bricklaying
  • render for masonry walls
  • bedding mortar for ceramic tiles and roof tiles
  • as grouting material.
  • The strength of mortars varies widely according
    to the ingredients used. Cement mortars are
    stronger than lime mortars and are more widely
    used today.
  • Portland cement and hydrated lime are factory
    produced.
  • Sands are excavated, washed and graded according
    to local supplies. Water for mortars should be
    clean and free of organic material. Water gives
    plasticity to the materials and in the case of
    cement, it is essential to the hydration process
    and resulting strength.

20
Properties of Metals
21
Introduction
  • Metals have been used by humans for over 6000
    years. The first metals were simply picked up off
    the ground, but in time people learnt to extract
    metals from their ores. Nowadays the technology
    has become quite complex and not only can many
    metals be extracted from their ores, but the
    properties of metals can be modified by various
    types of finishing processes or by mixing with
    other metals to form alloys. For building
    purposes, most metals are alloys.
  • The major base metals used are iron, copper,
    lead, zinc and aluminium. Metals using iron as
    their base are called ferrous metals while the
    others are termed nonferrous. Brass is an
    important nonferrous metal used in building,
    being an alloy of the base metal copper.
  • Glass today is manufactured from the same
    materials as it was several thousand years ago.
    Egypt is credited with the earliest glass making
    technology at least as early as 4000 BC. In
    Australia commercial glass making began in 1872
    in Melbourne with bottle manufacture. In 1903
    factories were established and in the 1920s and
    1930s products were increased to include window
    glass. Glass is manufactured commercially from
    sand (silica), soda and lime. Its characteristics
    are dependent on the proportions and treatment.

22
Learning outcomes
  • On completion of this unit, you should be able
    to
  • identify and name the metals commonly used in the
    residential building industry
  • understand the effects of the incompatibility of
    metals
  • state the application of the different metals
    used in building
  • list the different types of glass available to
    the building industry
  • state the uses of glass in residential building.

23
Properties of metal
  • Metals are substances that can either be hammered
    (the quality called malleability) or drawn out as
    wire (the quality called ductility) or melted and
    formed into shapes in moulds. Most metals can be
    polished. All metals are, to greater or lesser
    degrees, conductors of forms of energy such as
    heat and electricity.
  • Other characteristics possessed by metals may
    vary considerably from metal to metal. Some
    metals (eg stainless steel) have good strength
    qualities, whereas others (eg tin) have very
    little strength. All metals, however, will lose
    strength when repeated force is applied to thema
    process known as metal fatigue.
  • The degree of hardness of a metal will vary
    according to its natural characteristics (lead
    and tin, for example, are soft metals chromium
    and nickel are hard) and according to the degree
    to which the metal is worked. When a metal is
    worked at normal temperatures (by being rolled or
    forged, for instance) the result will be an
    increase in its hardness and strengththis it
    called work hardening.

24
Properties of metal
  • Most metals are subject to corrosion, which
    occurs when the surface of the metal combines
    with oxygen in the air to form a coat or crust
    that is no longer metallic (eg rust on iron or
    steel). Corrosive liquids and gases can actually
    eat away metals. (We can see the effect of salt
    air or spray on aluminium.) The process of
    corrosion is usually greatly speeded up by the
    action of heat and moisture. Some metals have
    very low corrosion-resistance, while others have
    a good degree of corrosion-resistance. Metals
    with a high degree of corrosion resistance (eg
    chromium) are often used either as coatings or in
    alloys with other metals to increase their
    resistance to corrosive agents.

25
Forming metals
  • How metals are formed depends upon the type of
    metal, the objects being made, and whether parts
    made of other metals are also incorporated. The
    following are some of the methods used
  • Casting where molten metal is poured into
    moulds and allowed to cool and harden. Rolling
    hot or cold metal is rolled between heavy rollers
    to produce various bars, strips, sheets or
    sections of metal.
  • Forging where hot metal is squeezed into shape,
    often using mechanical hammers and suitably
    shaped dies.
  • Extrusion where heated metal is forced through
    a suitably shaped hole in a hardened steel die to
    produce continuous solid or hollow sections.
  • Drawing wire or tubes are pulled through
    tapered dies to reduce the thickness of the
    metal. Normally the metal is cold and the process
    lessens its strength.

26
Joining metals
  • Metals can be joined by a variety of methods,
    including the following.
  • Mechanical joints Bolts, screws or rivets are
    used to join metal components together.
  • Soldering and brazing Most metals can be joined
    using an alloy which is a mixture of two or more
    metals that melt at a lower temperature than the
    melting point of the metals being joined.
    Soldering usually refers to tin-lead and
    lead-silver alloys which melt below 300C.
  • Brazing Gives stronger joints than soldering
    however, as it is done at higher temperatures
    (over 600C), brazing cannot be used on metals
    such as lead which have low melting points.
  • Welding Most welding involves a metal being
    heated to a temperature below its melting point,
    and the soft metal being hammered together. This
    traditional blacksmithing method has been
    replaced by gas welding (using oxyacetylene or
    propane) and arc welding (using an electric arc
    struck between the work and a welding rod or a
    carbon electrode).
  • Both brazing and welding involve heating the
    adjacent metal to extremely high temperatures
    which allow the metal to flow together and form
    one continuous unit.

27
Ferrous metals
  • Ferrous metals are those metals that contain a
    large amount of iron. The main types of ferrous
    metal are
  • cast iron
  • wrought iron
  • steels.

28
Manufacture
  • Iron ore, as mined, is a combination of iron and
    oxygen and various other substances. In this
    country most of the ore is obtained from open-cut
    mines.
  • The first step in processing the ore is to reduce
    it to metallic iron (often called pig iron), a
    process carried out in a blast furnace using coke
    as a fuel and reducing agent. The metallic iron,
    at this stage, contains a relatively high
    proportion of carbon (about 4 per cent).
  • To make steel, the carbon content of the metallic
    iron must be lowered to less than 1 per cent by
    an oxidation process in the steelmaking furnace.
    At the same time, the metal is given whatever
    special chemical and physical properties may be
    required by the addition of other metals. The
    quantities and timing of the additions of carbon
    and various other elements are carefully
    controlled to make the wide range of irons and
    steels that are available.

29
Effects of added elements
  • Carbon is the principal hardening element in
    steel. In plain carbon steels, it is used as the
    controlling element to regulate physical
    properties. When the carbon content is increased,
    hardness and tensile strength are improved but
    ductility and weldability are reduced (see Figure
    7.1).

Figure 7.1 Influence of carbon on the properties
of ferrous metals
30
Effects of added elements
  • Manganese increases strength and hardness but to
    a lesser degree than carbon. It also improves the
    toughness and abrasion resistance of steel.
  • Chromium increases hardening ability and tensile
    strength and improves corrosion and abrasion
    resistance. It is usually associated with nickel
    additions to form stainless steel.

31
By-products an recycling
  • Blast furnace slag
  • Blast furnace slag is the waste from the smelting
    process. It is an important by-product which can
    be used for concrete aggregate, road metal and
    slag wool for insulation.
  • Steel scrap
  • This is a major source of metallic iron for steel
    making. Scrap may either be residue left from the
    steelmaking process or purchased from discarded
    or obsolete constructions. About half of the
    crude steel produced annually in the world will
    eventually be returned to the steel-making
    furnaces.
  • Cast iron
  • Cast iron is produced by re-melting pig iron with
    steel and cast iron scrap. The cast iron has a
    high carbon content which makes it free-running
    and, therefore, very suitable for moulding
    intricate shapes. Cast iron has been used in the
    past for the decorative iron lace on buildings
    which is often wrongly called wrought iron.
    Cast iron is used for fire grates for soil waste
    pipes and ventilating pipes for drainage
    gratings and frames and for baths and basins
    (with a vitreous enamel finish).

32
By-products an recycling
  • Wrought iron
  • This is a low carbon iron which is excellent for
    forging but cannot be cast, tempered or welded
    (by gas or arc). Wrought iron was very popular
    for decorative finishes (such as balustrades and
    balcony railings) in the 1950s but has since lost
    popularity.
  • Steels
  • Steels are produced by removing impurities from
    pig iron and then accurately adjusting the
    quantities of all the ingredients. Steels are
    noted for their high strength compared to their
    production costs, and also for their poor
    performance in building fires. Ordinary steels do
    not resist corrosion well, but special steels (eg
    stainless steel) are produced today with
    excellent corrosion resistance.

33
Structural steel
  • Structural steel products are available in hot
    rolled sections and cold formed sections.
  • Hot rolled sections
  • These are formed while the steel is at elevated
    temperatures and include the following profiles

34
Cold formed sections
  • These are formed while the material is cold as
    distinct from materials that are shaped or worked
    while under the effect of heat. Unlike hot rolled
    sections, cold formed sections have constant
    thickness.
  • Cold formed sections may be formed by
  • Rolling in a rolling mill (for material up to 20
    mm in thickness), the product being what is known
    as cold rolled sections (see Figure 7.2).

Figure 7.2 Rolling in a rolling mill
35
Cold formed sections
  • Pressing by means of a press brake (for material
    up to 20 mm in thickness), the product being what
    is known as pressed steel sections (see Figure
    7.3).

Figure 7.3 Pressing with a press brake
36
Cold formed sections
  • Pressing by means of a swivel bender (for
    material up to 30 mm in thickness)the product
    being what is known as pressed steel sections
    (see Figure 7.4).

Figure 7.4 Pressing with a swivel bender
37
Use of structural steels
38
Pressed steel
  • Pressed steel is used for
  • door and window frames
  • metal trims (such as skirtings)
  • wall panels.
  • Note Pressed steel sections are limited to the
    size of the break press or, with swivel bending,
    are able to be produced economically in small
    quantities.

39
Alloy steels
  • Alloy steels contain certain added elements that
    provide special properties such as ultra high
    strength or resistance to corrosion or heat.
  • Stainless steel (containing chromium and nickel)
    is one such steel alloy which, although much more
    expensive than mild steel, is being increasingly
    used in building in a wide variety of
    applications because of its durability and low
    maintenance needs (even under extreme conditions
    of atmospheric pollution, as it has excellent
    resistance to corrosion).
  • Stainless steel has outstanding structural
    advantages because its hardness and toughness
    allows it to be used in very light sections, thus
    reducing greatly the weight of finished articles.
    Even more importantly, it is less affected by
    extreme heat, such as in a fire.
  • Except for very simple cutting or drilling on
    site, all shaping and fitting of stainless steel
    must be done in suitably equipped factories and
    workshops.
  • Stainless steel is also used for sanitary ware
    (eg sinks and benchtops).

40
Prevention of corrosion in steel
  • Upon exposure to the atmosphere ferrous metals
    combine with oxygen to form a red oxide (ie
    rust). Rust corrodes the metal and eventually
    wears it away, leaving behind a red powdery
    residue. This not only affects the appearance of
    the metal but substantially reduces its strength.
  • One way of making steel rust resistant is by
    applying one of many protective coatings
    available for steel products. These fall roughly
    into two groups metallic coatings and
    non-metallic coatings. As most require
    scrupulously clean conditions and special surface
    preparation of the steel for successful
    application, factory application of surface
    coatings is preferable.

41
Metallic protective coatings
  • These function by taking advantage of
    electro-chemical differences between different
    metals. In adverse atmospheric conditions it is
    the surface coating that is sacrificed rather
    than the base metal.
  • A number of methods are used to apply metallic
    coatings, such as electroplating, spraying and
    hot dipping. Metals used to coat the steel
    include cadmium, zinc, tin, aluminium and copper.
  • Zinc aluminium alloy applied by the hot dip
    process has effectively replaced galvanised steel
    in applications such as roofing because of its
    greatly increased durability.

42
Non-metallic coatings
  • These are available in a wide variety of colours
    and include
  • paints
  • baked epoxy finishes
  • vinyl coatings
  • bituminous coatings
  • vitreous enamel coatings.
  • Baked epoxy finishes are applied to
    zinc-aluminium coated steel which is chemically
    treated to assist bonding. An epoxy primer and
    then the final colour coat are baked on
    separately. This type of finish is popular for
    domestic and commercial roofing and wall cladding
    for normal conditions.

43
Non-metallic coatings
  • In marine and polluted industrial conditions
    steel can be coated with a tough vinyl which is
    laminated to the steel substrate. The vinyl
    coating locks out moisture, making an extremely
    corrosion-resistant finish.
  • Vitreous enamel coatings comprise a layer of
    glass fused to a properly prepared steel base.
  • Painting should be considered as a complete
    system that includes surface preparation,
    pre-treatment to facilitate adhesion, primer,
    intermediate coat or coats and finish coat.
    Different types of steel require different
    pre-treatments and coatings.
  • Bituminous coatings are based on bituminous
    resins such as coal tar or asphalt. The
    bituminous resins perform well underground and in
    contact with water but do not have good weather
    durability when exposed to sunlight.

44
Nonferrous metals
  • Most nonferrous metals are more costly to produce
    than ferrous metals. However, they often have
    much better working properties and resistance to
    corrosion. The more common nonferrous metals are
    copper, aluminium, zinc, lead, nickel, tin and
    cadmium.

45
Copper
  • Copper has been in use for at least 10 000 years
    nearly 5000 years ago it was being beaten into
    sheets, pipes, and other building products.
  • Copper is a pinkish coloured metal and is easily
    hammered into sheets. It is much more expensive
    than some alternatives but its extreme resistance
    to corrosion outweighs this disadvantage in
    certain applications. Upon exposure to the
    atmosphere, copper forms a protective copper
    oxide coating which is light green in colour.
  • Uses
  • Its resistance to corrosion has made it popular
    for use as water pipes and tanks. It also
    conducts electricity very well, hence its use for
    electrical wiring. Other uses include roofing,
    roof plumbing, flashing and damp courses

46
Brass
  • Brass is an alloy of copper and zinc, and is an
    attractive golden colour.
  • Uses
  • Brass is used for plumbers hardware (eg pipe
    connectors and fittings taps and outlet spouts,
    often chrome finished). Screws, nails, grilles,
    hinges, door locks and latches and chains are
    often made from brass.

47
Aluminium
  • Aluminium is a light-weight metal (approximately
    one-third the weight of iron) and is silver-white
    in colour.
  • Aluminium was introduced as a building material
    after World War Two in competition with
    traditional building metals, such as steel and
    copper. Probably the major characteristic that
    has helped aluminium gain widespread acceptance
    in the building industry is its suitability for
    extrusion production methods. This means that
    very complicated shapes can be produced
    economically.
  • Uses
  • Aluminium products are extensively used in the
    building industryfor domestic windows, doors and
    insect screens for commercial windows and
    curtain walls for residential and industrial
    roofing and rainwater goods for balustrades and
    railings and for reflective insulation.

48
Corrosion resistance
  • One of the most significant properties of
    aluminium is its excellent resistance to
    atmospheric corrosion. On exposure to the
    atmosphere, a whitish coating of aluminium oxide
    forms which then protects the surface from
    further corrosion. The structural integrity is
    not impaired as a result of this process.
  • Thus, untreated aluminium can be used for
    roofing, cladding and so on, but where long-term
    appearance is important the aluminium should be
    finished.

49
Compatibility with other building materials
  • Corrosion of a metal may be accelerated through
    contact with another metal of very different
    electro-chemical properties especially in the
    presence of an electrically conductive solution,
    such as sea spray or industrially polluted
    moisture.
  • Copper, brass and nickel alloys, all have a large
    potential difference to aluminium and in a salt
    solution cause it to rapidly corrode.
  • Some other building materials are also
    incompatible with aluminium and direct physical
    contact with those materials should be avoided or
    barriers should be used. Table 7.1 broadly
    indicates the types of barriers suitable for most
    building construction applications.

50
Finishes for aluminium
  • Although aluminium is naturally corrosion
    resistant, various finishes may be applied for
    aesthetic reasons. These include textured
    finishes ranging from a fine satin finish
    (achieved by chemical etching) to a
    scratch-brushed or hammered finish.
  • Bright finished aluminium can be achieved
    mechanically or chemically and results in highly
    reflective product. To retain the desired
    appearance, however, the sections should be
    anodised immediately.
  • Anodising is an electro-chemical process which
    greatly increases the thickness of the protective
    oxide film which would naturally form on the
    surface, thereby increasing the resistance of the
    surface to corrosion and damage and enhancing the
    appearance of the finished product. Film
    thicknesses can be specified for different
    applications.
  • The oxide film may be artificially coloured.
    Depending upon the process, however, some colours
    may be subject to ultraviolet deterioration and
    therefore are only suitable for interior
    applications.
  • Paint may be applied to aluminium but factory
    application is recommended as the process must be
    carried out in a dust-free environment and the
    aluminium surfaces must be pre-treated to remove
    surface contaminations and to provide a key for
    good adhesion. Powder coating is now widely used
    as a finish to aluminium in residential building.

51
Methods of joining aluminium sections
  • Most physical joining of aluminium elements is
    achieved with the use of bolts and nuts, screws,
    nails and rivets. For reasons of compatibility,
    fasteners are normally aluminium alloy, stainless
    steel or cadmium-plated steel.
  • Some modern adhesives such as epoxy and epoxy-PVC
    types are commonly being used to produce
    high-strength joints between aluminium and a
    great variety of other materials.
  • Welding is also used to join aluminium. If welded
    assemblies are subsequently anodised, some
    discolouration in the anodised film occurs across
    the welded zone.

52
Zinc
  • Zinc is a soft, greyish metal which can be
    hammered or rolled into sheets such sheets have
    been used for roofing rainwater goods. Today,
    zincs most important function in the building
    industry is as a protective coating on steel.
  • The zinc coating acts first as a barrier to
    corrosion. However, should the coating be
    scratched or damaged, exposing the steel, the
    zinc surrounding the damaged part will itself
    corrode instead of the steel. Thus by sacrificing
    the zinc the steel is protected and will not rust
    until all available zinc is used.

53
Zinc-aluminium coating
  • Research has produced a protective coating for
    steel which combines zinc and aluminium in an
    alloy. It is easily applied, by hot dipping, and
    holds to the metal better than zinc galvanising,
    thus giving much better protection. It is used on
    sheet steel and cladding.

54
Lead
  • Lead is soft and easily worked, but its great
    density makes it heavy to handle, and thin sheets
    and pipes will not even support their own weight.
  • Lead has been used for thousands of years lead
    water pipes were used by the Romans, and our word
    plumber comes from the Latin word plumbum
    meaning lead.
  • Due to its toxic properties, however, lead is no
    longer used for water pipes. In the past, it was
    used for roofing and roof plumbing, but today its
    use is limitedalthough in certain roof plumbing
    situations, its weight and malleability still
    make it a useful and preferred material.
  • Uses
  • Lead is used
  • for flashing and damp coursing
  • for solder (as an alloy with other metals)
  • as sheet lead lining for sound proofing.

55
Nickel
  • Nickel is a hard, silvery-white, malleable metal.
    It is resistant to corrosion.
  • Nickel is used
  • on steel as a base for chromium plating
  • as a constituent of stainless steel
  • as a nickel alloy (known as Monel metal).

56
Tin
  • Tin is a very costly, soft, weak metal with a low
    melting point (232C), but extremely resistant to
    corrosion.
  • Uses
  • Tin is used
  • as a coating on sheet steel (tin plate)
  • for solders.

57
Cadmium
  • Cadmium is a white, malleable metal that looks
    like tin.
  • Uses
  • Cadmium is used
  • for electroplating steel components (such as
    screws, latches, handles, locks)
  • as plating on brass plumbing fittings, locks,
    latches, handles and other such fittings.

58
Chromium
  • Chromium is well known for its high resistance to
    corrosion as a plating, and as a constituent of
    stainless steels and other corrosion-resistant
    alloys. It is extremely hard and scratch
    resistant.

59
Stainless steel
  • Stainless steel is far harder than mild steel and
    silvery in appearance. It has wide applications
    in commercial buildings and has been used
    extensively for domestic sinks. More recently it
    has been used for bench tops and as a termite
    barrier where it takes the form of a very fine
    mesh which termites cannot penetrate.

60
Metal frame construction
  • Domestic and commercial buildings can both be of
    metal frame construction. This type of
    construction is versatile, light, strong, time
    and labour saving, economical, and stable. Walls,
    roofs and floors can all be constructed this way.
  • The metal frames made from steel are
    pre-fabricated in the workshop or before being
    erected. They can be joined together using
    rivets, welds, screws or bolts.

Figure 7.6 Metal framing for a brick veneer house
61
Fasteners
  • The wide range of metal fasteners used to join or
    fix building materials and components includes
  • nails
  • screws
  • bolts, nuts and washers
  • timber connectors and framing anchors
  • masonry anchors.

62
Screws
  • Screws are available in a range of sizes, shapes
    and coatings for use with wood or masonry.
  • The four most common types of wood screw are
  • countersunk head
  • round head
  • raised head
  • coach screws (see Figure 7.8).

63
Bolts, nuts and washers
  • Bolts, nuts and washers are normally made of
    plain steel, alloy steel or a non-ferrous metal,
    and may have a protective metal coating (such as
    zinc or cadmium). The bolt heads are usually
    either dome headed with a square shank dome
    headed with a slot hexagonal or square headed.
    The nuts may be square or hexagonal and the
    washers are flat discs with a cental hole. The
    two most common types of bolt are
  • the coach (or cup head) bolt
  • the hexagonal head bolt (see Figure 7.9).

64
Timber connectors and framing anchors
  • These are used for joining various timber-framing
    members. They are made from hot-dipped galvanised
    steel and are strong and quick to install. Figure
    7.10 illustrates some of them, together with
    their methods of fixing.

65
Masonry anchors
  • Masonry anchors are used in concrete or masonry.
    A strong fixing is provided by the casing
    expanding into the hole as the nut or bolt is
    tightened. A masonry anchor may be placed into a
    mortar joint but is far more effective if placed
    in the body of the masonry.
  • The two most common types are
  • the Loxin
  • the Dynabolt (see Figure 7.11).

66
Glass
67
Manufacture
  • The art of glass-making is very old and, today,
    the industry still uses basically the same raw
    materials as the ancient glass makers.
  • These basic ingredients are
  • silica (from sand)
  • soda (sodium carbonate)
  • lime.
  • With the addition of varying quantities of
  • dolomite
  • feldspar
  • soldium sulphate
  • cullet (broken glass)
  • decolourising or colouring agents.
  • The major constituent, silica, is the
    glass-former while the other minerals act as
    fluxes and refiners in the melting process. The
    raw materials are mixed together and melted at
    approximately 1500C and then cooled to a
    workable temperature of about 1000C, finally
    hardening at about 500C.

68
Glass used in building
  • Different applications require glass of different
    thicknesses and properties. The sheet size of the
    glass area is important for instance, larger
    windows require thicker sheets of glass, both for
    self-support and to resist pressure from wind
    loads.
  • Glass is specified by its thickness, method of
    manufacture and function. Information is readily
    available from the manufacturers.

69
Glass used in building
  • Glass used in building falls into the following
    categories
  • float glass
  • sheet glass
  • plate glass
  • toughened glass
  • heat absorbing glass
  • light and heat reflecting glass
  • patterned or figured glass
  • laminated glass
  • wired glass.

70
Float glass
  • Floating is the most common modern method for the
    production of high quality glass for building. It
    involves a continuous process in which the molten
    mixture passes to a float bath where it is
    supported on molten tin. As the ribbon of glass
    passes through the float bath it is slowly cooled
    and fed onto rollers (see Figure 7.12).

71
Sheet glass
  • This is an older method which produces
    transparent glass that is not perfectly flat. A
    ribbon of molten glass is drawn between rollers
    through a cooling chamber (see Figure 7.13).

72
Plate glass
  • This method has been largely superseded by the
    float glass method. It produces a greater range
    of thicknesses than the drawn sheet method
    because the process is continuous. The molten
    glass is drawn between metal rollers and then
    between a twin grinder unit which polishes both
    surfaces simultaneously.

73
Toughened glass
  • This is produced from ordinary glass by thermal
    treatment of the finished product. The resultant
    surface tension across the sheet causes the glass
    to fracture into small particles when cut so that
    once the glass product is so treated it cannot be
    further modified or cut on site. Toughened glass
    is three to five times stronger than ordinary
    glass with regard to sustained loads and impact
    but the surface is no harder than ordinary glass.
    This type of glass is commonly used for frameless
    glass assemblies.

74
Heat absorbing glass
  • This is produced by the addition of certain
    minerals during melting. It significantly reduces
    solar heat gain and glare in a building by
    absorbing between 50 and 90 per cent of the
    infrared rays and 30 and 75 per cent of the
    visible light rays. As a result, this glass tends
    to expand and contract more than other types of
    glass and suitable tolerances must be left in the
    frame sizes. Heat absorbing glass is available in
    a small range of tints.

75
Light and heat reflecting glass
  • This is produced by coating the glass surface
    with metallic films. With the use of this glass,
    solar radiation can be reduced by up to 70 per
    cent. Frequently this glass forms part of a
    double-glazing system which protects the coated
    surface.

76
Patterned or figured glass
  • This is produced by passing a ribbon of molten
    glass between rollers during the cooling process
    so that a pattern is pressed into the glass.

77
Laminated glass
  • Glass layers are bonded together by heat with a
    polyvinyl butyral interlayer between the glass
    layers. This technique produces shatterproof and
    safety glass such as bullet-proof and
    cyclone-resistant glass, one-way glass and heat
    and light reflecting glass.

78
Wired glass
  • Wired glass incorporates a layer of the fine wire
    mesh and is an earlier form of safety glass used
    for industrial glazing, balustrades, shower
    screens and so on. It is also used as a
    fire-retardant glass in some situations.

79
Properties of glass in buildings
  • Thermal performance
  • Glass expands and contracts on heating and
    cooling and, to prevent the kind of disasters
    which happened with early glass curtain-walled
    skyscrapers, this should be taken into account in
    the design.
  • Stresses can be set up in the glass resulting
    from differences in expansion rates between
    frames and glazing, especially where frames are
    metal.
  • Thermal insulation
  • Single glazing offers little thermal resistance
    but the effect of an air gap created by double
    glazing almost halves the heat loss through a
    single pane.
  • The optimum gap is about 20 mm. Heat absorbing
    and reflecting glasses make an effective
    contribution to minimising solar heat gain (see
    Figure 7.14).

80
Properties of glass in buildings
  • Acoustic performance
  • For any degree of sound insulation, double
    glazing is essential. Sound reduction values vary
    according to the thickness of the glass and the
    width of the gap.
  • Fire resistance
  • Although non-combustible, ordinary glass breaks
    and then melts in fires and double glazing offers
    no significant advantage over single glazing.
    Certain special glasses offer some degree of fire
    resistance.

81
Alternative glass products
  • Glass fibres
  • Glass fibres are very strong and flexible for
    their size. They are used in electrical elements
    and insulators. In addition, their transparent or
    translucent qualities make them suitable for
    globes and light shades.
  • Electrical goods
  • Because of its high electrical resistance, glass
    is frequently used in electrical elements and
    insulators. In addition, its transparent or
    translucent qualities make it suitable for globes
    and light shades.
  • Glass bricks
  • Glass bricks can form a semi-transparent wall
    which is self supporting but not structural. This
    was a popular building material prior to World
    War Two, at which time production was
    interrupted, but it is again becoming popular.
  • Recycled glass products
  • Much glass-making involves the recycling of old
    glass but glass products have been used in
    alternative ways as building materials. Glass
    bottles, for instance, have been built into
    walls. When filled with water, such walls can act
    as heat storage banks which can be seasonally
    adjusted.

82
Summary
  • Metals
  • Metals are widely used in the building industry.
    Some common metals and their applications are
  • steelframing and cladding materials
  • leadflashings
  • copperplumbing pipe and fittings and electrical
    cable
  • brasstapware and pipe fittings, door hardware
  • zincprotective coatings
  • aluminiumwindow and door framing, roof cladding.
  • Some metals require protective coating to fulfil
    their service. Steel and aluminium in particular
    have to be protected from corrosion by the
    elements and generally most metals should not be
    allowed to come into contact with each other.

83
Summary
  • Glass
  • Glass is manufactured from silica, soda and lime.
    Different applications require glass of different
    thicknesses and properties. In particular, larger
    sheet sizes will require thicker glass to resist
    pressure from wind loads. Glass is specified by
    its thickness, method of manufacture and
    function.
  • The main use of glass in building is for windows
    but other functions include lighting and
    translucent bricks.

84
Timber
85
Introduction
  • On the successful completion of this course, you
    will have achieved a Statement of Attainment for
    units
  • BCGBC4006A Select Procure and Store construction
    materials
  • BCGBC4007A Plan building or construction work
  • BCGBC4008A Construct on site supervision of a
    building or construction project

86
Introduction
  • Learning outcomes
  • On the completion of this unit you will be able
    to
  • Understand the basic characteristics of wood
  • Determine the factors that affect the durability
    and strength of timber
  • State the main causes of defects in timber
  • Classify the main types of timber and
    manufactured boards according to their use.

87
Introduction
Tree growth A tree trunk is really a very long
cone, not a cylinder (see Figure 2.1 in the
guide). The height increase in the trunk or
lengthening of a branch is due to growth at the
extreme tips. The trunk does not get longer
between branches it gets thicker to support the
weight of the growing tree. Cells under the bark
produce this thickening of the trunk. In cool
climates there is a definite seasonal pattern in
softwoods and hardwoods, and this is often seen
in the growth rings. Counting growth rings can be
used as a rough guide to the age of a tree, but
the accuracy of this method can be affected by
drought, by irregular growth conditions and by
where the sample is taken in the trunk.
88
Introduction
Sapwood and Heart wood Sapwood Sapwood extends
from the growth cells under the bark, (the
cambium layer) into the trunk for a short
distance. It is made of newly formed wood cells
which contain food (including starch) and
water. Heartwood (or truewood) see Figure
2.2. Heartwood (also often called truewood)
extends from the sapwood through towards the
centre of the tree. These cells do not contain
any food or starch. Heartwood is formed from the
gradually dying sapwood. It contains tannins and
other materials, making it usually darker and
more durable than sapwood.
89
Introduction
Figure 2.2 Section across a tree trunk, showing
its structure
90
Introduction
Softwoods and Hardwoods Timbers are divided
into two groups Softwoods or non-pored
timbers Hardwoods or pored timbers. Non-pored
(softwoods) Oregon, Radiata pine, Canada pine,
Redwood, Western red cedar, Cypress pine,
Queensland pine, Hoop pine, Baltic pine Note All
pines and firs are softwoods Pored
(hardwoods) Tallow wood, Brush box, Black butt,
Red gum, Spotted gum, Blue gum, Mountain ash,
Stringy bark, Iron bark, Mixed hardwoods, Silky
oak, Silver ash, Queensland maple, Red cedar,
Pacific maple, (Meranti) Black bean, Blackwood,
Ramin, Note All eucalypts are hardwoods
91
Introduction
Soft wood and Hardwood Study Figure 2.3 and
2.4 detailed illustrations of the Structure of
Softwood and Hardwood contained in the guide.
The composition of wood The chemical
composition of wood is very complex. The main
constituents are Cellulose
Lignin. Other substances are also present.
One such group is the extractives.
92
Introduction
Cellulose Cellulose is a complex carbohydrate
that makes up the cell walls in plant tissue, it
is what gives wood its tensile strength.
Cellulose is the main component of pulp and
paper. Lignin Lignin binds wood fibres
together, giving wood its structural strength. It
is plastic when hot, which is why heated or
steam-treated timber is much easier to bend.
93
Introduction
Extractives Extractives are substances in
wood that can be extracted by being dissolved in
solvents. They include sugars and starches in the
sap, oils and resins (which give many woods their
characteristic smells) and tannins. Resins are
present in many pines, in Douglas fir and Oregon.
A high concentration of resins can greatly
increase the durability of some woods in two
ways less moisture absorbent Deters
invading organisms. Answer the questions in
your guide
94
Introduction
Resins Because they flow when heated, resins
may exude as sticky drops through surface
coatings of stains, paints and other treatments.
Kiln drying of such woods reduces this
risk. Similarly, rose mahogany and northern
silky oak sometimes exude gums which have a
harmful effect on finishes, and where it is
necessary to apply surface finishes, these
timbers should, if affected, be
avoided. Tannins are present in all woods,
although some trees contain quite a lot more
tannin than the average. When tannin comes into
contact with metal, the timber will stain (for
fuller details see the section later in this unit
on stains in wood). Complete the questions in
the guide
95
Introduction
Conversion into timber Sawing methods There
are two main sawing methods live sawing Sawing
around. Live sawing Live sawing is the
simplest way of sawing a log and involves sawing
through and through (see Figure 2.5 in your
guide), using large circular saws (band
saws). Live sawing is well suited to fast,
large-scale production from small logs of good
form with few defects. Can result in a large
number of seasoning faults (warps, twists,
cupping etc). Figure 2.5 Cross-section through
live sawn log
96
Introduction
Figure 2.5 Cross-section through live sawn log
97
Introduction
Sawing around Sawing around Involves turning
the log during the sawing process so that a
number of different cutting directions are
obtained. The most common method of sawing around
used in Australia is back sawing (see Figure
2.6), but quarter sawing is also used. Back
sawing Back sawing takes longer than live sawing
but is more flexible and enables high grade
timber to be produced from faulty logs. Figure
2.6 Examples of back sawn and quarter sawn logs
98
Introduction
Figure 2.6 Examples of back sawn and quarter
sawn logs
99
Introduction
Quarter sawing Quarter sawing is the only
sawing method that reveals the decorative
features in some figured timbers (eg Queensland
walnut and maple). Some coarse-textured timbers
give a harder wearing board when quarter sawn as
it reduces the effect of detrimental gum veins in
some eucalypts, and quarter sawn timber dries
more slowly and is less likely to develop defects
and distortions in seasoning.
100
Introduction
Seasoning Seasoning is a process of drying out
the green timber to a desirable level. This
reduces the chance of the timber shrinking,
splitting or deforming when used. Drying makes
the timber lighter, increases its strength and
prevents its deterioration from fungal decay or
attack by some insects. Green, sappy wood will
not easily take paints, glues and stains, and
will exude sap and moisture. Seasoning is
carried out by stacking the timber and allowing
it to dry out naturally in the air drying it out
more quickly in controlled-heat kilns a
combination of air and kiln seasoning. The
seasoning process has to be controlled to prevent
unacceptable shrinking, splitting or warping and
twisting.
101
Introduction
Stress grading Timber is stress graded to
determine the amount of bending stress it can
safely withstand. This allows timber to be used
safely and efficiently. There are two methods
for stress grading timber Mechanical. Visual
grading Visual grading occurs when experienced
graders inspect timber and grade it by eye.
102
Introduction
Mechanical grading Timber is fed into a
machine which applies continuous stress along the
length of the timber and then marks it with
spray-on coloured dyes (the colour of the dye
indicating the stress grade). Sometimes one
length of timber will be marked with more than
one colour to indicate changes in its strength.
The stress grades and colours are shown in Table
2.2 (the higher the number, the greater the
stress it can withstand). Table 2.2 Stress
grades and colour codes for timber Stress grade
Colour code, F4red, F5black, F7blue, F8green,
F11purple
103
Introduction
Timber sizes Timber is sold as either Sawn
timber (i.e. as it comes, straight from the
saw) Dressed timber sawn timber that has been
machine-dressed straight and flat all round. In
most instances standard lengths start at 1800 mm
(or 1.8 m) and increase in units of 300 mm up to
6300 mm. Quantities of timber can, however, be
produced to special lengths to order. Dressed
timber can be specified as the finished size or,
more commonly, as the original sawn size from
which it is dressed. A piece of 100 (75 timber,
for example, will measure several millimetres
less on each face when dressed, due to planing
and sanding. The symbol (or ex) means out of
thus 100 (75 means that the piece is dressed
from a sawn section of 100 (75.
104
Introduction
Milled (or dressed) timber Timber that has
been machine-finished to a particular width and
thickness or has been machined to a specific
shape is called milled or dressed
timber. Milled timbers include the
following Square and rectangular
sections Tongue and groove boards Weatherboard
s and wall panelling Mouldings. Study the
sections and mouldings in your guide and answer
the questions
105
Introduction
Features of wood Physical characteristics The
appearance of wood is affected by various
physical characteristics texture grain figure
knots hardness wear.
106
Introduction
Features of wood Texture Wood texture is caused
by the size and arrangement of the cells, and by
variations in the density of the wood. We speak
of fine, coarse, even or uneven
textures. Grain Grain refers to the general
direction of growth of the wood tissue, and is
shown by the way the fibres separate when a piece
of timber is split. We can have, for example,
straight, spiral, interlock, curly, wavy or cross
grain (see Figure 2.11) Figure 2.11 Timber
showing some types of cross grain
107
Introduction
Features of wood Figure Figure refers to the
ornamental patterns seen on the dressed surface
of the timber and is the result of colours and
grain patterns in the wood. Knots Knots occur
where the branches joined the trunk of the tree.
They are harder and darker in colour than the
stem wood (see Figure 2.12). Figure 2.12
Timber knots
108
Introduction
Features of wood Hardness Hardness is how well
a material resists being dented. Hardness varies
from tree to tree, and also within a tree. End
grain is sometimes harder than side grain, and
sometimes softer. Figure 2.13 shows a number of
timbers, listed in order of hardness.
109
Introduction
Features of wood Iron bark Hardest Grey
box White mahogany Turpentine Brush
box Silver top ash Stringy bark Karri Tallow
wood Jarrah Cypress pine Radiata pine Douglas
fir (North America) Red cedar Softest
110
Introduction
Features of wood Wear Some timbers have a
greater resistance to wear than others, a
consideration that is particularly relevant to
floors. Generally, hardwoods with a relatively
high density, with a fine, even texture and small
pores are most suitable for industrial or heavy
duty floors. Stains Some stains occur naturally
in wood. Lets look at some of the most common
types and sources of stains in timber.
111
Introduction
Features of wood Surface stains from
moulds Mould stains develop on sawn timber in
the early stages of drying. They do not damage
the wood and are removed when the timber is
dressed. Sap or blue stains Blue stain fungi
may attack the sapwood and heartwood of both
softwoods and hardwoodsplantation pines are
especially susceptible. To stop this, it is
important that the tree is seasoned quickly after
felling, especially in the warmer months. The
strength of the timber is not particularly
affected, but the appearance can be streaked and
ugly.
112
Introduction
Features of wood Decay discolour Pockets or
streaks of red-brown or whitish wood may indicate
decay. Such wood may be considerably softer than
the surrounding wood. This material is often
brittle and will usually break if you attempt to
prise it out with a knife. This decay is stopped
by seas
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