Construction technology is the study of the ways structures on sites are built by human beings. Many procedures should be followed from the time the construction of the foundation of the house starts till the completion of the house. The site on which the building is to take place should be flat without hillocks and lumps. (Tony, 2005)
To ensure that the ground is level a bulldozer is used to go over the land with its blades close to the ground to remove all hillocks and lumps. Laying stilts out can be done if the plot is on a severe incline to layout a floor on top of them. To raise the ground to the required level filling has to be done.
This procedure is the first step in construction and it is referred to as site preparation and grading. The foundation of the house is an integral part of house building. It is the part where the whole house rests on. Sand should not be used because a firm foundation is a must to make the completed house stronger. (Roger, 2007)
Concrete is used in most constructions because it forms a firm foundation. A trench is dug and the concrete laid up to 3 to 4 feet deep and this provides a very solid foundation for whatever material is used for building. Many operations are required to construct the foundation up to but not including the Dpc or the damp proof course which is a horizontal barrier designed in a wall to prevent the moisture from rising by capillary action through the structure through a phenomenon popularly known as rising damp.
Most countries have standards that require most buildings to incorporate a damp proof course during the time of construction which may consist of a course of engineering slate or brick, a thin strip of plastic or even a layer of bitumen. Where a damp proof course is not available or is inadequate there many ways that can be used to fit one because it is a must that a house be fitted with one.
In most advanced construction areas a common method in masonry walls require holes to be drilled into the walls at intervals that are regular and a chemical (silicone) which has a high penetrating rate injected into the holes. Absorption of the chemical occurs in the walls where it dries up to form a barrier that is water proof. Concrete cavity fill is a method that is used to stabilize sand, gravel, rocks, crushed stones and concrete structures which are porous, cracked or have other cavities that are difficult to seal or access the same against the water flows.
The first step in concrete cavity fill include injecting a low viscous and a pumpable aqueous and aerated concrete which has a pore volume of 20 percent or less into the cavities that are to be sealed. The above aerated concrete is first injected at a low pressure so that it remains intact.
The second step that is carried out in concrete cavity fill is increasing pressure to exert the aerated concrete in. It is further pressed into the cavities. The aerated concrete that is aqueous which comprises of a dispersing agent, a finely ground cement and optionally fine particulate material which has a large surface area makes the existing air bubbles to collapse when its is pressed further into the cavities so that the escaping air from the air bubbles entrains the fine particulate material and the cement into the cavities.
This results into hydration and sedimentation. The aerated concrete according the above claim has an air pore volume of 35-80 percent and it is not spontaneously miscible with water but it is hydrophobic. The aerated concrete according to the above claim also contains an anionic surfactant which has the general formulae (R) m -R1 – (SO3 M) 2 (1).
It also contains a retarder, an accelerator or a thickening agent which ensures that all the cavities are well sealed off. The injection of the concrete is carried out at a pressure that is below 3 bars and gradually the pressure is raised to 6 bars. The aerated concrete that is hydrophobic mixes with water spontaneously has finely grounded cement and the particle distribution ensures that 95 percent of the particles pass through a screen with a mesh which has the size of 64 βm.
It contains a fine particulate material which has the size smaller than that of cement. It has a hydrophobizing dispensing agent and a resin that forms air pores in correct amounts to form or produce at least twenty percent of the pore volume. To be more effective in cavity fill the aerated concrete has the following constituents, air pore volume of at least 40- 90 percent, 0.1-1.5 by weight of a dispersing agent, 40-90 parts by weight of water, and by weight of a fine particulate material it contains 2-11 percent. It also has 0-3 parts of resin weight which weights 10000 in molecular terms.
It contains an accelerator, a thickening agent or a retarder of between 0- 2.5 parts and this serves the purpose of controlling hydration of the cement or increasing the concrete viscosity gradually. The concrete cavity fill is therefore one of the operations that is carried out before the Dpc or the damp proof course.
Another operation that would be required to construct the foundation up to the Dpc is the hardcore backfill. The materials used in hardcore backfill should be suitable and of good quality about the purpose and conditions of their use. Particular care should be observed in ensuring that hardcore back filling materials have been verified to establish whether they are fit for the construction purpose.
Visual, chemical and other analysis can be used to determine the constituents of the aggregate, stone, ground formation and other materials. In this respect the hardcore backfill, bedding, concrete constituents as well as similar materials should be properly evaluated to ensure that they are suitable and stable to withstand pressures under all conditions. Under floor fills that are excessive in depth should be avoided. The building regulations require that moisture and contaminants be excluded from buildings. Traditionally, hardcore specifications require that the materials be clean and well graded, materials be granular, properly graded and crushed rocks as well as properly graded gravel.
The bed of hardcore should be well compacted and well drained to form a firm foundation or a firm level base. A suitable hardcore back fill material ensures that the rest of the building that will lie on it will be firm thus avoiding cracks and other anomalies once the building is completed.
In this respect all the hardcore backfill materials should go through the laboratory check ups and experiments to ensure that they are suitable to serve the desired purpose. This is therefore an operation that occurs in the process of house construction up to but not including the damp proof course.
Insulation is a fundamental principle in construction. Insulation is the procedure that is followed in ensuring that there is thermal conformability in the interior environment. It therefore works to reduce heat losses into a relatively cold environment from a relatively warm environment.
This process is achieved through several ways which include limiting heat loss through convection and for this to happen, fibre glass and polystyrene which contains cellular structures that trap air are used. Insulation also helps reduce or limit heat loss through radiation by the use of insulating materials that are generally good at reflecting the heat to avoid the loss by radiation. Insulated panels made of shiny metals such as aluminium are used because they are good at reflecting heat. It also occur up to but not including the damp proof course. (Chudley, 2005)
Various materials are brought to the site of construction using different means such as lorries and tractors which carry stones, sand, gravel and hardcore used for backfilling. The bull dozers are used to make well levelled paths that can be used by the tractors and the lorries especially on hilly areas to minimize the occurrence of unnecessary damages to the site.
After the materials are offloaded from the tractors and lorries they are then spread all over the foundation that has been dug using the bulldozers. Spreading the hardcore can be done by hands to ensure that there is no place in the foundation that has not been filled correctly.
The lorries and the tractors also serve the purpose of carrying away the soil, that is, the waste from the site to ensure that there is a smooth flow of operations. In addition heavy graders are used to crush the hardcore as well as ensuring that it is evenly spread all over the surface of the foundation.
The gravel is then poured on top to fill up the small holes that remain uncovered by the hardcore. Again the grader runs over the surface to ensure that the gravel is firmly embedded in the hardcore. This operation ensures that the foundation is firm to support any other operation that will take place. (Mark, 2006)
In case there is water at the site as a result of rains or water gushing out from the ground, it is pumped from the site using high speed water pumps to completely drain the site before any other operation takes place. This is because the hardcore that is used in the backfilling need to be dry and free from moisture which would otherwise weaken its ability to hold the weight of the house. (Michael, 2007) Another temporary work that would be required in the site would include some form of breaking the hardcore using metallic equipments such as a hammer especially in the corners of the foundation where the grader would not reach.
If the construction site is on a hilly ground it would be unsafe to drive without proper considerations of the conditions of the lorry or other heavy machines to be used in delivering the material. This is because if the brakes are not in good condition and the lorry carries hardcore up the hill it might run down the hill thus endangering the lives of many people.
Inhaling the hardcore and soil dust during the delivery and the removal of the waste may result into persistent coughing. The right clothing should therefore be put on to prevent the occurrence of such incidents. Since some activities may require the use of a hammer to break the hardcore that lies at the corners of the foundation and which the grader might not have reached it is important to put on hard eye glasses to prevent particles falling into the eyes.
In concrete cavity fill some chemicals are used and they may be harmful to one’s health. This calls for one to put on the correct protective clothing to prevent inhaling the chemical. Continuous inhaling of the cement dust is also quite harmful to the health and it is therefore important to put on the right clothing to prevent the dust from entering through the mouth and the nose.
During the foundation preparation it is important to clear the bushes nearby to have enough space for pouring materials. Once the materials have been used up grass should be planted on the bare ground to prevent soil erosion. (Danrny, 2001). Any hole dug around the construction site to preserve water should always be covered at the top using hard materials that can not converge inwards once a person or an animal steps on it.
After the construction is over it is wise to fill up the hole. Several general observations can be made from the above scenario. First, any construction must be certified by the necessary authority who gives a go ahead into the kind of construction that is to take place in any place. (Roy, 2006) The owner of the house is legally liable to abide by the rules that govern the construction of houses in a certain place.
Secondly, house construction is procedural and needs the expertise knowledge who asses all the conditions necessary for the construction. Thirdly, there are health safety measures that should be observed in every kind of construction work and finally there are also environmental risks that should also be observed by the constructors.
References
Tony, B. (2005), construction technology. Analysis and choice, (New York, McGraw Hill).
Roy, C. (2006), contemporary legislation and practice, (New York, New York Press).
Roger, G. (2007), introduction to building, (New York, Prentice Hall).
Mark, W. (2006), how decisions and processes are achieved in the world of construction, (New York, New York Press).
Chudley, R. (2005), construction engineering, (Oxford, Oxford University Press).
Michael, C. (2007), construction technology for tall buildings, (Oxford, Oxford University Press).
Danrny, W. (2001), safety features in a construction site, (Oxford, Oxford University Press).