Sub-strand 2: Resistant materials

DEFINITION:

These are materials that are not pliable or flexible and cannot be easily compressed with bare hands. Resistant materials have properties such as;

1. Compressive resistance
2. Tensile strength
3. Ductility
4. Malleability
5. Elasticity

TYPES OF RESISTANT MATERIALS

Resistant materials are put into groups such as;

1. Plastics
2. Wood
3. Metals
4. Ceramics
5. Glass

SOURCES OF RESISTANT MATERIALS

1. Plastics-The sources of plastics are either natural or synthetic. Natural plastics come from trees and other plants, animals horns and milk for glues, and insects (polish from shellac).

B. Synthetic Plastics-Most plastics today are synthetic and come from crude oil. Some of the these plastic materials include; Poly Vinyl Chloride(PVC), Polystyrene, Polyethylene and Acrylic.

2. Wood- Timber is the source of wood. It is first felled by either chain saw or axe, cut into planks, battens and scantlings and then seasoned naturally by drying or artificially by the kiln. Some of the wood are, odum, mahogany, odanta, ofram, teak, oak, ebony, blackwood, African walnut, emire, and softwoods like, redwood, cedar, pine, and onyina etc.

3. Metals- Metals are used extensively in everyday life for several different ways, construction, cooking, automobiles, currency coins etc. Metals are extracted from the soil through mining of the ores. The ores are the solid materials called minerals which occur in rocks in the earth’s crust. Some of the metals include, aluminium, copper, iron, tin, zinc, lead, etc.

4. BUILDING MATERIALS

These are materials that are used for construction, they are either natural or artificial.

The natural building materials include clay, sand, wood, stones and leaves.

Sand-Pits, rivers, sea

Stones- Rocks and sea

Clay-Earth

Laterite-This is sand mixed with stones and small amount of clay and obtained from the soil after digging the topsoil.

ARTIFICIAL MATERIALS–(LIME)

1. Lime is obtained by burning limestone (chalk) to produce quicklime. Water is then added to increase the quantity in a process called slaking.
2. Cement-This is produced from limestone, clay and water.

TYPES OF CEMENTS

1. Ordinary Portland cement
2. Water-proof cement
3. White cement
4. Rapid hardening cement
5. High sulphate -resisting cement

HOW CEMENT IS MANUFACTURED

2.