Cement mortar is an intimate mixture of cement , sand and water. Cement is the binding material, and sand is the fine aggregrate. The binding material (cement) develops when water is added to the mixture. Sand suitable for cement mortar include, river sand, gutter or pit sand.

Sand used for cement mortar must have the following properties;

• should be chemically inert.
• It should be free from organic or vegetable matter.
• Should not contain salt.
• Should contain sharp, angular, coarse grain that is well graded and hard.

Preparing cement mortar.

Cement and sand in the required ratio is first thoroughly mixed in dry condition then water gradually added and mixed until required consistency is achieved.

Cement to sand ratio for various works;

• Masonry Works :   1:6 to 1: 8
• Plastering:    1:3 to 1:6

Mortar Curing.

Curing is the process of ensuring sufficient moisture during hardening of mortar. Curing is ensured by spraying of water. It starts 6 – 24 hours after mortar has been applied

Characteristics of Cement Mortar;

• Cement sand ratio mix richer than 1:3 is prone to shrinkage.
• Mortar with well-proportioned mix gives an impervious surface.
• Mortar with leaner mix may become porous.
• Strength of mortar depends on the cement sand ratio.

Compressive Strength of various cement sand ratios;

• 1:3 –   10N/mm2
• 1:4 –  7.5N/mm2
• 1:5 –   5.0 N/mm2
• 1:6 –   3.0 N/mm2
• 1:8 –    0.7 N/mm2

Uses of cement mortar.

• To bind masonry units like blocks and bricks.
• Plaster walls and slab.
• Give neat finishes to walls and concrete works.
• Fill joints and cracks in walls.
• As filler material in stone masonry.

Timber is wood used for building/construction works. Timber means ‘to build’. A felled tree is first cut into sizes of suitable lengths called rough timber that are transported to timber yard. By sawing rough timber, it is converted into various commercial sizes like planks, battens, posts, beams etc. Such form of timber is known as converted timber.

Properties of timber suitable for building construction.

• Should be uniform in colour.
• Should have pleasant  odour when freshly cut.
• Clear ringing sound when struck indicates the timber is good.
• Good timber should have good texture
• The timber should be of high density
• Timbers should be strong and durable.
• Good timber do not warp under changing environmental conditions.
• Timber should be capable of resisting shock loads.
• Good timber do not deteriorate due to wear. This property should be looked into, if Timber is to be used for flooring.
• Timber should have high strength in bending, shear and direct compression.
• Timber should have high modulus of elasticity.
• Good fire resistance.
• Low water permeability.
• Good workability, should not clog the saw.
• Capable of resisting the action of fungi and insects attack.
• Timber should be free from defects like dead knots, shakes and cracks.

How timber Can be Preserved

Timber is preserved by protection from fungi and insects attack. Timber should be well seasoned before preservatives are applied. The following are the widely used preservatives:

Tar: Hot coal tar is applied to timber with brush. Tar coating protects the timber from attack of insects and fungi.

Paints: Paint improves the appearance of the timber. Solignum paint is a special paint which protects the timber from the attack of termites.

Chemical salt: These are the preservatives made by dissolving salts in water. The salts used are copper sulphate, masonry chloride, zinc chloride and sodium fluoride.

Creosote: Creosote oil is obtained by distillation of coal tar.

Uses of Timber in construction

•  Construction of columns, trusses, piles.
•  Making of doors, windows, flooring and roofing.
• Construction of railway sleepers, fencing poles, electric poles and gates.
•  For temporary works such as scaffolding, centering, shoring and strutting, packing of materials.

Structural analysis which involves strenuous mathematical calculations is a core skill required for civil and structural engineers. Almost every project handled by a civil/ structural engineer will involve structural analysis.

Structural analysis can be very tedious and when there are many projects to be done, moving from one mathematical calculation to the other may eventually lead to frustration and then errors.

There are many structural analysis/ design software available that make analysis and design very easy, however , there are free structural analysis software available which can ease analysis and design, one of them is the RC 21 Sub-frame analysis excel program (RC 21) developed by reinforced concrete council UK.

RC 21 analyses reinforced concrete frame structures to BS 8110. While the United Kingdom no longer uses the BS 8110 and adopted the Euro code, BS 8110 is still being used in many African countries, and also other countries outside Africa.

RC 21 analyses reinforced concrete elements based on input parameters to determine design moments and shear forces necessary to further calculate amount of reinforcement required.

You can watch the video on how RC21 works, by clicking the my youtube video link below.

https://www.youtube.com/watch?v=kkTyB3cFkn4

RC 21 can analyze slab, beams and columns. It can analyze up to six spans and seven supports.

Input parameters required for analysis to complete include;

Dead and live loads.

Span (slab/beam length)

Beam/slab/column section dimensions (size)

End conditions

Load factor

Colum height above/below beam level.

Results calculated include design slab, beam and column moments and shear forces. RC 21 considers 3 load cases and calculates design moments based on worse case loading. RC 21 is a free excel program, to down load, you can visit the following URL; REINFORCED CONCRETE FRAME ANALYSIS TO BS 8110.

You can also directly view and download RC 21 by clicking HERE

The excel program will open in your browser, to download finally, click the download icon at top right of your screen.

RCC21 sub-frame analysis is a spreadsheet program to calculate design moments for reinforced concrete elements such as slabs, beams and columns. The spread sheet program uses moment distribution method and considers critical load cases in the calculation of design moments.

It can analyze up to six spans and determines beam and column moments, and also slab moments as the case may be.

Generally for analysis to complete, you will be required to input span lengths, beam or slab section dimensions, dead and imposed loads, column height above and below beam section, column section dimensions and much more.