CopperCopper is more malleable – it issofter and can be shaped and bentmore easily.

It is a better conductor ofelectricity and therefore used inelectrical wires.

When copper corrodes, the rustcreates a waterproof barrier andtherefore used as a roofingmaterial.

Copper is very easy to recycle, Thecopper you see around has not beenmanufactured, but is reused.

India is one of the most significantsuppliers of copper.

Aluminium

Energy

Most common element onearth

Takes huge amounts ofenergy to extract

Once extracted, very easyto recycle

Is used in manufacturing oflarge parts of cars,aeroplanes

Used in alloys to createstrong but lightstructures

Non-corrosiveIs used in construction

fieldShorter lifespanComparatively expensive

What is Corrosion? Degradation of metals’ properties due to the interaction with air

and water, is called Corrosion.

Atoms on the surface of the metal reacts with Oxygen atoms inthe air.

This forms an oxide.

Oxides are weak and brittle, so they damage the material.

Iron forms iron oxide.

Copper forms copper oxide.

Aluminium forms aluminium oxide.

These are slow processes.

Corrosion of metals can be controlled by different methods such aspainting the surface or applying a layer of other non-corrosive metal

In case of aluminium, a thin layer of aluminium oxide forms on the metal surface which protects the inside metal from further corrosion. In effect, aluminium forms its own protective coating against corrosion.This behaviour is beneficial for us and different from iron’s which expose the metal’s surface to further corrosion.That is why, aluminium is used in many places instead of iron.

How corrosion can be stopped?• Physical Barriers:

Coating a metal by paint Or plastic

• Alloys:

Combination of one metal with another

metal or non-metal is called alloy.

Stainless Steel is iron alloyed with

chromium and nickel. Chromium forms a

protective oxide layer, just like

aluminium.

• Galvanic Protection

Stainless Steel

Protective chromium oxide layer

Galvanic Series

Magnesium

Zinc

Aluminium

Iron/Steel

Brass

Copper

Stainless Steel

Reac

tivi

ty

Facts

Attaching a more reactive metal to a less reactive metal stops theless reactive metal from corroding. Zinc is more reactive thansteel, so when attached to steel, the zinc corrodes faster than itwould on its own. The steel corrodes (rusts) much slower than itwould on its own.

Cars are ‘galvanised’. The chassis parts are passed through moltenzinc to produce a zinc coating. This is better than simple paintbecause even when the coating is scratched the car won’t rust.

Same with roofs – this is what is meant by ‘GI’ roof (galvanisediron).

You can see the zinc plates on this steel ships hull. They prevent itfrom rusting. However, after a few years the zinc will be used up,and the item will continue to rust unless repainted/new zinc blockis attached.

Wood

Softwood – coniferous Hardwood - deciduous

Wood expands and shrinks according to humidity. It is Flammable.

There is danger of damages by termites/rot.

Damage of wood because of termites can be controlled by Chemical Treatment on the wood. It must be applied before seasoning.

Wood is made up of long carbon chains (cellulose and lignin). Toughness of wood comes from fibrous quality of wood.

Umbar Tree

Eucalyptus Tree

Jackfruit Tree

Mango Tree

Seasoning Of WoodWood is stored out in the open, out of direct sunlight. Wind and Sun dry wood

naturally over 6-12 months. This is inexpensive but time consuming method of seasoning the wood.

Kiln – It takes 2-3 weeks to dry the wood but it is expensive process.

Advantages of seasoning of wood: Removes moisture, prevent rotting, wood becomes lighter and hence cheaper to transport, more receptive to preservatives/paint/glue, better insulating qualities, stronger.

Disadvantages of seasoning of wood: As moisture leaves wood, it shrinks. Can cause warping and cracking and weakening of the timber in hardwoods, as the ends dry faster than middle part of the wood.

Air dried – natural way of wood seasoning Kiln dried

Facts

Cement is made from clay, limestone and sand. Limestone is hard andbrittle, you can crack it into small pieces with a chisel and hammer. Clay is nothard because it only contains small amount of calcium carbonate. Sand is madeof silicon oxide. This is very strong and hard – similar to diamond in atomicstructure.

Cement making is where these 3 types of rocks are heated to hightemperature so they react, and then cooled. The further addition ofwater, bonds calcium and silicon together to make a very strong substance, likenatural rock. However, unlike natural rock, you can transport it (cement is lightwhen in dry powdered form), and you can easily shape it when wet, intowhatever is required.

+

Concrete can be used to make construction bricks. They are cheaper thanfired bricks, and also more insulating as they contain air gaps.Concrete may be used for non load bearing walls and foundations.Concrete may be used to bear large loads, though it should be reinforced.Under load, concrete may bend putting it into tension. Reinforcement isrequired to carry tensile loads and prevent cracking and failure of theconcrete.

Precautions to take while using Concrete

Tamping

No tamping-poor quality concrete (Honeycombing)

Curing - enough water to give maximum strength to concrete

While working with concrete, your own safety is equally important. Always use:

Result of not taking safety measures

Papercrete

+ + = Papercrete

Advantages:

It is strong for its weight, asit is an incredibly lightmaterial.

It is an outstanding insulator.It resists fire to a good

extent.It is simple to produce.It is very cheap.

Disadvantages

Tendency to absorb hugeamounts of waterfrom rain and fromthe ground ifdirectly in contact.

It becomes soft because ofmoisture.

If placed in wet areas, itgrows mould.

Papercrete is a recent invention, a material under development. It isnot approved by the international code council as a load bearingmaterial, but many people are experimenting with its uses.

Cement Paper water