The basic structural elements of buildings will be discussed under five subheadings including; slab, beam, column, wall and roof.
Slab is the large flat horizontal element of a building. (Pavement) and usually spans between beams or walls. Slabs can be made of wood, concrete, or interlocking blocks or bricks, although slabs made of concrete are the most common. In storey buildings, slabs are usually supported on beams or columns.
Beams are horizontal load bearing members. In its basic form, the main function of a beam is to transfer slab and wall loads to the columns. Depending on the type of building in terms of strength and materials, beams can be made of wood, concrete, reinforced concrete or steel.
Columns are the vertical load bearing members of a building and their main function is to transmit beam, slab, wall, roof, as well as live loads safely down to the foundation of the building. Depending on strength requirements and specifications, columns can be made of wood, reinforced concrete or steel.
Walls are usually vertical members and can be built of wood, bricks, blocks or concrete. Walls within a building would be constructed to have openings for doors and windows where appropriate. Walls can be load or non load bearing. A simple example of a load bearing wall is a situation where the wall directly supports the roof of a building.
Roof is the upper covering of a Building. Its main function
is to protect the building from rain and heat from the sun. Roofs can either be
flat or pitched.
Stones are naturally available building materials that
have been used since early civilization. Type of stones used in civil/ building
construction works are igneous, sedimentary or metamorphic in origin. Stones
required for building/civil engineering construction must be strong, durable,
hard, tough, and cost effective.
Uses of stones in building/civil engineering
For construction of foundations, walls, columns and arches
For flooring and damp proof courses
Facework of buildings, paving of roads and base courses
Abutment and bridges, dams and retaining walls
Common building stones
The following are some commonly used building stones
An igneous rock. Colour varies from dark grey to black. Used in road construction and as aggregates for making concrete.
An igneous rock. Crystalline in structure. Particles sizes ranges from fine to coarse grained. They are used for dams, river walls and bridge piers. Also used as coarse aggregates in concrete.
Sand-stones are stratified rocks consisting of quartz and feldspar. They come in many colours including white, grey, red, yellow, brown and dark grey. Sandstone is not as strong as granite and balsalt. They are used for masonry work, dams, bridge piers and river walls.
Slates are metamorphic rocks composed of quarz, mica and clay. Their colour varies from dark grey to black. They are used for roofing tiles, pavements etc.
This is also a type of metamorphic rock with porous structure. Its colour varies, i.e. brown, red, yellow, grey etc. laterite is commonly used as filling material.
Another type of metamorphic rock. Marble is available in different colours such as pink and white. Used for facing and ornamental works.
Cement is produced by burning a mixture of calcium and clay material at very high temperature then grinded to produce fine powder.
Types of cement.
Cement comes in many varieties. Some are briefly explained below.
Ordinary portland cement;
The most used type of cement in general concrete construction. It is suitable when there is no danger of exposure to sulphates in the soil.
Quick setting cement;
Quick setting cement is produced by reducing the percentage of gypsum and adding a small amount of aluminium sulphate during production. This type of cement starts setting around 5 minutes and hardens within 30 minutes. Quick setting cement is used to produce concrete for underwater construction.
it is made from oxides of manganese,iron and chlorium. It is used for plastering, ornamental works, fixing of marbles and tiles.
Rapid hardening cement;
This type of cement gains strength earlier than ordinary Portland cement and consequently speeds up construction activity.
Coloured cement is produced by mixing pigments with ordinary Portland cement. Pigments such as colbalt produces blue colour, iron oxide produces brown, red or yellow colours.
Low heat cement;
When heat produced by hydration of cement does not get easily dispersed, it may give rise to cracks, hence in such situations it is preferable to use low heat cement.
High alumina cement;
This type of cement is produced from a mixture of lime and banxite. It is resistant to sulphate and acid attack.it is used in underwater construction.
Acid resistant cement;
This is cement made by adding acid resistant materials such as quartz, quartzite, sodium silicate or soluble glass. Acid resistant cement is commonly used in construction of chemical factories.
Common problems of fresh concrete will be discussed
under 4 modes which are: inadequate workability, segregation, bleeding and
Workability is the ease at which concrete can be placed and compacted. When inadequate, it leads to segregation and bleeding. Workability depends on quantity of water, shape of aggregates and their percentage in concrete.
This is the separation of coarse particles in green (fresh) concrete. It happens due to insufficient finer particles. Segregation can also be caused by throwing concrete from great heights at time of placing. Segregation causes loss of cohesiveness in concrete which results in honey combing and loss of strength.
The appearance of water with cement particles on surface of freshly laid concrete. Caused by excessive quantity of water in the mix or too much compaction. Bleeding causes pores to form on concrete and renders it weak.
Fresh concrete is said to be harsh when it becomes difficult to obtain a smooth surface finish. It is caused by insufficient quantity of fine aggregates or insufficient quantity of water.
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