Some of the factors militating against the industrial development in Nigeria are Government’s inconsistent monetary and financial policies as well as poor public services and excessive tariffs on utilizes. All these have added to the negative performance of both the public and the private sector industries. (Sanusi, 2002).
2.2 ENGINEERING MATERIALS AND PROPERTIES
Engineers of today have so many materials available to them for construction purposes. Some of these include timber, stone, clay, cast irons, copper alloys and so on. Also, industrial ceramics and fibre reinforced composite materials have come into use in recent decades.
In earlier times, with a much smaller number of materials available engineers often produce their designs and products by a process of trial and error. Some engineering materials are detailed below. (Arthur, 2004).
2.2.1 CEMENT AND CONCRETE
A cementitious material is one that has the adhesive and cohesive properties necessary to bond inert aggregates into a solid mass of adequate strength and durability. Portland cement which was first patented in England in 1824 is by far the most common. It’s a finely powdered, grayfish material that consists chiefly of calcium and aluminum silicates. The common raw materials from which it is made are limestone which provides caO and clays or shale, which furnish SiO2 and Al2O3. These are grounded, blended, fused to clinkers in a kiln and cooled. Gypsum is added and the mixture is ground to the required fineness. (Arthur, 2004).
Concrete is a carefully proportioned mixture of cement, water, fine aggregate and coarse aggregate. To these basic components a variety of admixtures are frequently added. As soon as the components of concrete have been mixed together, the cement and water react to produce a cementing get that bonds the fine and coarse aggregates into a stone-like material. The chemical reaction between the cement and water, an exothermic reaction producing significant quantities of heat is termed hydration. (Kenneth, 1997).
2.2.2 AGGREGATES AND SAND
An aggregate is a material in inert form and it occupies about 70-75 percent of the volume of the hardened mass of structural concrete thereby contributing to its strength. The gradation of the particle sizes in the aggregate is important in order to produce a densely packed aggregate which will increase the durability and economy of the concrete. Natural aggregates are generally classified as find and coarse. Fine aggregate is any material that passes a No. 4 sieve requirements for satisfactory aggregates are found in ASTM C33, “standard specification for concrete aggregatesâ€.
Construction sand are found almost everywhere in this country (Nigeria). The most suitable sands for concreting include river or sea well as dune sands. Sands that are loose sediments of rock construction should not be used unless subjected to special treatment.
(Arthur 2004).
2.2.3 TIMBER AND PLYWOOD
Timber can be classified into softwood and hardwood. Wood is one of the oldest natural construction materials. It is a cellular organic material composed principally of cellulose and lignin. Softwood comes from coniferous trees and hardwood comes from deciduous trees having broad leaves. Because of its fibrous nature, wood is highly anisotropic, the tensile and comprehensive strength are much greater along the grain. The only way in which the anisotropy of wood may be overcome is by bonding thin layers together as plywood. Plywood contains an odd number layers in order that shrinkage stresses shall be symmetrical about the centre with a consequent minimum of warping (Leonard,1991)
2.2.4 STEEL
Steel is an alloy consisting almost entirely of iron in combination with small quantities of various elements. A wide range of properties may be achieved by varying the composition of the steel. Carbon is the element that has the greatest effect on the properties of the steel. Up to a point, increasing the carbon content increases the hardiness strength and abrasion resistance of steel. However, ductility, toughness, impact properties and mach inability will be decreased.
The making of steel from pig iron is essentially a refining process. Carbon, silicon, phosphorous and sulphur levels of the pig iron n reduced permissible by the steel specification. Other alloying elements be added to the mix to produce steel having the desired properties. The most commonly used processes to change the pig iron to steel are the open-earth process, the electric furnace process and the basic oxygen process. The four general categories of steel that we have are: carbon steel, alloy steel, stainless steel and structural steel (Leonard, 1991).
