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