Construction Hints

Production of Portland cement starts with two basic materials; a Calcareous material and an Argillaceous material.  The calcareous material is a calcium oxide, such as limestone, chalk, or oyster shells, the Argillaceous material is combination of alumina and silica obtainable from clay, shale, and blast furnace. the materials are passed through a grinding mill, using wet or dry process to the kiln.  In the kiln, the raw materials are melted at temperature of 1400 oC  to 1650 oC,  changing the raw materials into Cement clinker which is then cooled  and stored. The final process involved grinding the clinker into a fine powder, adding gypsum to regulate the setting time if the cement in the concrete. The final product can be transported in stored bulk or sacks.

Portland Cement concrete is most widely used manufacturing construction material...it is very important in the construction field, it is used in structures such as buildings, pavements, Dams,factories, bridges etc. Portland Cement concrete main constituents is the Portland Cement ( i.e Dangote cement) ,aggregates, water, air voids,  and in some cases, admixtures. Portland Cement is an instant glue when water is added to it and bonds aggregate to together to make Portland Cement concrete.

These are materials (usually metals) which have unfilled valence bond and thus provide vacant energy states into which electrons in the valence state can move. The movement of electrons is an electric field is facilitated by gain of velocity and momentum as it moves towards the positive electrode. This is due to added energy which therefore requires an occupied energy State at a higher level. Example of conductors are Cu, All, Fe, etc. Metals with few electrons in their valence make excellent conductors of electricity. Forms of conductor are wires, cables and bus-bars (rods, tube etc)

An aggregate can be defined as the material comprising of percentage required of gravel, crushed stone, and sharp sand of their specific size of particle mixed together at a required ratio to form part of concrete mortal. Aggregates can be classified as Natural and Artificial. Natural Aggregates: Coarse Aggregates, fine Aggregates, Sand  and gravel Aggregates, Granite Aggregates,

These are metals in which the valence band are completely filled and electrons are readily available for movement into the conduction band and creating an electron-hole pair in the structure of the material and apparent electrical conditions. Examples of semi conductor materials are group IV elements such as carbon, silicon, germanium, tin. Semi conductor can be classified into two forms : Intrinsic and Extrinsic semi conductor

The Strain developed in a material is directly proportional to the Stress producing it. Thus there is linear relationship between stress and strain which is tenable within certain limits for most materials

Stress: This is the intensity of the internal force, which is the magnitude of the sum of forces within a section, is divided by the cross-section. Stress = F/A. (N/m²) Strain: This is the change in the dimension(s) of a material in a state of stress. It can either be comprehensive or tensile. Tensile stress results in extension  of length while comprehensive stress shortens the length of a material. Strain = L-Lo/ Lo

1. Strength : The ability if a timber to withstand stress or external load.    i.e   -Bending parallel to the grain,   -Compression parallel and     perpendicular to the grain,    -Tensile parallel to the grain    -shear parallel to the grain. 2. Elasticity: modulus of elasticity by Inertial. Elasticity = Elasticity x Inertial

1. Density: This is the ratio of mass per volume of a timber structures. Timber with a close packed grain tends to handle a high density than those with much spaced grain. 2. Seasoning: This is process of reducing moisture content from from timber. 3. Thermal conductivity. 4. Thermal Expansion.

Factors are used in all engineering design to allow for variability in loading, material, workmanship etc..which can not be define with absolute certainty, here, the strength of the material or structural element must always exceed the effects of loadings by margin of its factor of safety. Factor of safety =  material strength/design load or Ultimate stress/actual stress NB:- Safety factor applied at one point in design is called overall safety factor, Applied at several points is called partial safety factors.

In engineering, it is called the safety margin required in order to insure safety during loading or the remaining strength after load is applied. It can also be said to be how much of structures total capacity is held in reserve during loading of structural elements. Margin of safety = (Failure load/Design load ) - 1

Defect of timber is any features that lowers the technical or commercial value of timber and may leaf to its rejection or its relegation to a lower grade. Example of such are ; Twisting, Decay, swelling etc

Nigeria timber is graded into 7 groups. From N1 - N7 ( according to NCP 2: 1973) u can get copy from Standard Organization of Nigeria SON. N1 is the highest strength Class N7 is the weakest strength Class. Most construction work in Nigeria is done with grading from N4 - N7 ( soft woods). Some of its grading includes; N1 - strongest wood i.e Ekki. N2 - AYO N3 - iroko ( teak), N4 - Abura N3-N4 - Obeche . . N7 - Araba, Apu (softest wood)

Seasoning of timber is the process of allowing timber to dry under atmospheric conditions or reducing moisture content from timber.. This could be Naturally or Artificially induced seasoning.. 1. Natural seasoning : Allowing timber to dry without direct sun light exposure. This could take as much as 6 months. 2. Artificial seasoning : drying of timber using oven. This could take 2 weeks.

Timbers is that part of tree that can be used for structural proposes/construction and carpentry. MECHANICAL properties of timber includes; 1. Strength :- this is the ability of timber to withstand stress or external load. i.e . Bending stress, compression stress, tensile stress, shear stress. 2. Elasticity :- EI Its ratio if Modulus of elasticity to its inertial. PHYSICAL properties of timber includes; 1. Density : this is the ratio its mass and volume. Timber with a close packed grain tends to handle a higher loading than those with much spaced grain. 2. Thermal Expansion. 3. Thermal conductivity 4. Seasoning : this is process of reducing moisture content from timber. This could be natural seasoning or artificial seasoning.

The slenderness ratio of a member is the ratio of the effective length to the appropriate radius of gyration (SR = Le/r or KL/r). NB: this is valid only when the column has equal unbraced heights for both axes and end conditions are same for both axes.