Miscellaneous Building Materials

Glass, plastics, bitumen, asbestos, paints, distemper and varnishes are some of the miscellaneous materials used in building constructions. Their properties and uses are briefly presented below,

GLASS

Silica is the main constituent of glass, But it is to be added with sodium potassium carbonate to bring down melting point. To make it durable lime or lead oxide is also added.

Manganese oxide is added to nullify the adverse effects of unwanted iron present in the impure silica. The raw materials are ground and sieved.

They are mixed in specific proportion and melted in furnace, Then glass items are manufactured by blowing, flat drawing, rolling and pressing.

Important Properties of Glass

It absorbs, refracts or transmits light. It can be made transparent or translucent.
Can take excellent polish.
It is an excellent electrical insulator.
It is strong and brittle.
Can be blown, drawn or pressed.
It is not affected by atmosphere.
It has excellent resistance to chemicals.
And available in various beautiful colours.
With the advancement in technology, it is possible to make glass lighter than cork or stronger than steel.
Glass panes can be cleaned easily.

Types of Glass

Soda Lime Glass:

It is mainly a mixture of sodium silicate and calcium silicate. It is fusible at low temperature. In the fusion condition it can be blown or welded easily. It is colourless. It is used as window panes and for the laboratory tubes and apparatus.

Potash Lime Glass:

It is mainly a mixture of potassium silicate and calcium silicate. Also known as hard glass. It fuses at high temperature. It is used in the manufacture of glass articles which have to with stand high temperatures.

Potash Lead Glass:

It is mainly a mixture of potassium silicate and lead silicate. It possesses bright lustre and great refractive power. And used in the manufacture of artificial gems, electric bulbs, lenses, prisms etc.

Common Glass:

It is mainly a mixture of sodium silicate, calcium silicate and iron silicate. It is brown, green or yellow in colour. Mainly used in the manufacture of medicine bottles.

Special Glasses:

Properties of glasses can be suitably altered by changing basic ingredients and adding few more ingredients. It has now emerged as versatile material to meet many special requirement in engineering.

PLASTICS

Plastic is an organic material prepared out of resin. It may or may not contain fillers, plasticisers and solvents. Plastic may be defined as a natural or synthetic organic material which are having the property of being plastic at some stage of their manufacture when they can be moulded to required size and shape.

Shellac and bitumen are the natural resins used as plastic for a long time. In 1907, Black land produced synthetic resin from the reaction of phenol and formaldehyde. The resin was hardened under pressure and heat to produce useful plastic articles.

Types of Plastics

Primarily there are two types of plastics:

Thermosetting Plastics:

It needs momentary heated condition and great pressure during shaping. When heated cross linkage is established between the molecules and chemical reaction takes place. During this stage shape can be changed with pressure. This change is not reversible.
The scrap of such plastic is not reusable. Bakelite is an example of such plastic.

Thermoplastic:

In this variety, the linkage between the molecules is very loose. They can be softened by heating repeatedly. This property helps for reuse of waste plastic. These plastic need time to cool down and harden. These plastics are to be kept in moulds till cooling takes place completely. Bitumen, cellulose and shellac are the examples of this variety of plastics.

Properties of Plastics

Colour: Some plastics are completely transparent. Using pigments plastics of any attractive colour can be produced.
Dimensional Stability: It is dimensionally stable to a great extent.
Durability: Plastic offers great resistance to moisture and chemicals and hence more durable.
Electrical Insulation: The plastics possess excellent electrical insulating property.
Fire Resistance: The phenol-formaldehyde and urea-formaldehyde plastics resist fire to a great extent and hence they are used as fire proofing materials.
Strength: The plastics are reasonably strong. Their strength may be increased by reinforcing with various fibrous materials. Attempts are being made to produce structurally sound plastics.
Specific Gravity: The specific gravity of plastics is very low and hence convenient to handle.
Ductility: The plastics are not ductile and hence they fail without giving warning.
Fixing: Plastics can be bolted, drilled, glued, clamped or simply push fitted in position.
Maintenance: There is no maintenance cost for plastic articles i.e., they do not need painting and polishing.

Uses of Plastics

There are variety of plastics made to suit different uses. The typical uses of plastics in buildings is listed below:

Corrugated and plain sheets for roofing.
For making jointless flooring.
Flooring tiles.
Overhead water tanks.
Bath and sink units.
Cistern hall floats.
Decorative laminates and mouldings.
Window and door frames and shutters for bathroom doors.
Lighting fixtures.
Electrical conduits.
Electrical insulators.
Pipes to carry cold waters.

BITUMEN

Asphalt, bitumen and tar referred as bituminous materials, which essentially hydrocarbon materials. The asphalt a mixture of inert mineral matter lime alumina, lime, silica etc. and a hydrocarbon known as asphaltic bitumen. In some places like Trinidad and Bermudez, asphalt is available in nature at a depth of 3 to 60 metres.

It known as natural asphalt. Common variety used all over the world residual asphalt, which obtained by fractional distillation of crude petroleum oil. Bitumen is the binding material which is present in asphalt. It is a hydrocarbon. It obtained by partial distillation of crude oil. Contains 87 per cent carbon, 11 per cent hydrogen and 2 per cent oxygen.

Tar obtained in the destructive distillation of coal, wood or other organic materials. When coal or wood heated to redness in an closed chamber, it yields volatile product and residue coke. After separating and cooling volatile product gives tar.

Sr. No	Property	Asphalt	Bitumen	Tar
1	Colour	Blackish Brown	Dark with slight reddish tinge	Deep Dark
2	Colour Content	Low	Moderate	High
3	State	Solid Or Semisolid	Solid	Viscous Liquid
4	Effect On Heating	Burns with a smoke Melts Becomes more flame and becomes fluid. plastic	Melts	Become More Fluid
5	Setting Time	Less	Less	More
6	Adhesive Power	Less	Less	Most
7	Resistance To Acid	More	More	Less
8	Use	As damp proof course, for paints, as roofing felt and for road works	As damp proof course and as roofing felt.	For preserving Timber.

Comparison between asphalt, bitumen and tar.

ASBESTOS

Asbestos is a general name for several varieties of fibrous minerals which are available in nature. But presently, most of the commercial asbestos produced is ‘chriotile’ [Mg6SiO11(OH)6.H2O].

Properties of Asbestos

It is flexible, soft and non-porous.
It is fire proof and acid proof material.
A good insulator of heat and electricity.
When it mixed with cement and water, it retains shape firmly.
Its colour is brown or grey.
It can cut into pieces or can drilled.
It possesses high tensile strength in the direction of its fibres.
Its specific gravity is 3.10.

Uses of Asbestos

Asbestos cement sheets are the cheapest roofing materials.
Asbestos cement pipes used as down take pipes of rain water from the roof.
With bitumen it forms good damp proof layer.
It used for preparing fire proof ropes and clothes.
Used as covering material for fuse and electric switch boxes.
It is useful for insulating boilers, furnaces etc.

PAINTS

Paints applied on the surfaces of timber, metals and plastered surfaces as a protective layer and at the same time to get pleasant appearance. Applied in liquid form and after sometime the volatile constituent evaporates and hardened coating acts as a protective layer.

Constituents of Paint

The essential constituents of paints are:

Bases: It is a principal constituent of paint. It also possesses the binding properties. It forms an opaque coating. Commonly used bases for paints are white lead, red lead, zinc oxide, iron oxide, titanium white, aluminium powder and lithophone. A lead paint is suitable for painting iron and steel works, as it sticks to them well. However it affected by atmosphere action and hence should not used as final coat. While zinc forms good base but is costly. Lithophone, which is a mixture of zinc sulphate and barytes, is cheap. It gives good appearance but affected by day light. Hence it used for interior works only.

Vehicles: The vehicles are the liquid substances which hold the ingredients of a paint in liquid suspension and allow them to applied on the surface to painted. Linseed oil, Tung oil and Nut oil used as vehicles in paints. Of the above four oils, linseed oil very commonly used vehicles. Boiling makes the oil thicker and darker. Linseed oil reacts with oxygen and hardens by forming a thin film.

Pigment: Pigments give required colour for paints. They are fine particles and have a reinforcing effect on thin film of the paint.

The common pigments for different colours are:

Black:-Lamp black, suit and charcoal black
Red:-Venedion red, red lead and Indian red.
Brown:-burned timber, raw and burned sienna
Green:-chrome green, copper sulphate.
Blue:-Prussian blue and ultra marine
Yellow:-ochre and chrome yellow.

The Drier: These are the compounds of metal like lead, manganese, cobalt. The function of a drier is to absorb oxygen from the air and supply it to the vehicle for hardening. The drier should not added until the paint is about to used. The excess drier is harmful because it destroys elasticity and causes flaking.

The Thinner: It known as solvent also. It makes paint thinner and hence increases the coverage. It helps in spreading paint uniformly over the surface Terpentine and neptha commonly used thinners. After paint applied, thinner evaporates and paint dries.

Properties of an Ideal Paint

It should be possible to apply easily and freely.
Should dry in reasonable time.
It should form hard and durable surface.
It should not be harmful to the health of workers.
Should not easily affected by atmosphere.
It should possess attractive and pleasing appearance.
It should form a thin film of uniform nature i.e., it should not crack.
Should possess good spreading power.
It should be cheap.

Types of Paints

Depending upon their constituents there are various types of paints. A brief description of some of them which commonly used given below:

Oil Paint: These paints applied in three coats-primer, undercoat and finishing coat. The presence of dampness while applying the primer adversely affect the life of oil paint. This paint is cheap and easy to apply.

Enamel Paint: It contains white lead, oil, petroleum spirit and resinous material. The surface provided by it resists acids, alkalies and water very well. It desirable to apply a coat of titanium white before the coat of enamel applied. It can used both for external and
internal walls.

Other Types

Emulsion Paint: It contains binding materials such as polyvinyl acetate, synthetic resins etc. It dries in 1 1/2 to 2 hours and it is easy to apply. It more durable and can cleaned with water. For plastered surfaces, first a coat of cement paint should applied and then the emulsion point. Emulsion paint needs sound surfaces.

Cement Paint: It is available in powder form. It consists of white cement, pigment and other additives. It durable and exhibits excellent decorative appearance. should applied on rough surfaces rather than on smooth surfaces. And applied in two coats. First coat applied on wet surface but free from excess water and allowed to dry for 24 hours. The second coat then applied which gives good appearance.

Bituminous Paints: This type of paint manufactured by dissolving asphalt or vegetable bitumen in oil or petroleum. It is black in colour. It used for painting iron works under water.

Synthetic Rubber Paint: This paint prepared from resins. It dries quickly and is little affected by weather and sunlight. It resists chemical attack well. This paint may applied even on fresh concrete. Its cost is moderate and it can applied easily.

Aluminium Paint: It contains finely ground aluminium in spirit or oil varnish. It is visible in darkness also. The surfaces of iron and steel protected well with this paint. It widely used for painting gas tanks, water pipes and oil tanks.

Anti-corrosive Paint: It consists essentially of oil, a strong dier, lead or zinc chrome and finely ground sand. It is cheap and resists corrosion well. It is black in colour.

Application of Paint

Preparation of surface for application of paint is the most important part in painting. The surface to painted should not oily and it should be from flakes of the old paint. Cracks in the surface should filled with putty and then with sand paper. Then primer applied. Painting work should carried out in dry weather. The under coats and first coats must allowed to dry before final coat applied.

DISTEMPERS

Distempers are the cheaper variety of paints in which chalk used as base and water used as a carrier. The emulsifying agent which commonly used is glue or casein. Distempers are available in powder form or in the form of paste. They mixed with hot water before use.

The surface to distempered should thoroughly rubbed and cleaned. The cracks, if any should be filled by lime putty. Surface should kept dry for about two months before applying distemper. Thus a primary coat applied and allowed to dry. Distemper usually applied in two coats.

Properties of Distemper

They are generally light in colour.
The coatings are generally thick.
They give reflective coating.
They are less durable than oil paints but are cheaper.

VARNISHES

Varnish is the solution of resins or resinous substances like amber, copal, shellac, gum resin etc. in solvents like oil, turpentine, alcohol etc. Depending upon the solvents used varnishes are classified as, oil varnishes, turpentine varnishes, spirit varnishes and water varnishes.

The desirable characteristics of an ideal varnish are,

It should give glossy surface.
Should be durable.
It should dry rapidly after application.
It should not develop cracks after drying.
Commonly used on wooden surfaces.

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Ketan Pattekar

Author & Editor Of This Blog.

Founder Of “KPSTRUCTURES”