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Aluminium Composite is a composite sheet material which it has high strength and good rigidity. Thus , it has outstanding deflection capacity and bending strength. It also has very good impact resistance. Aluminium Composite has great weather resistant, extreme temperature resistant and corrosion resistant. Thus, it has high durability.
Besides, it enables creative design possibilities which allows shaping and formation without losing the surface integrity that is optically flat. It can be reformed and shaped to specific requirements that resulted a smooth and attractive finish. Therefore, it can be said to have superior flatness to other cladding products which is ideal for creating smooth and monolithic surfaces.
In addition, it is light in weight and reduces the use of frame lodgings. As a result, the cost of fabrication and installation is reduced. Besides, it also has excellent acid, alkali and salt spray resistant and also pollution resistant. Moreover, it also has low resonance factor which able to minimize the unwanted vibration noise. Thus, the installation can be carried out in a quieter condition.
Moreover, it has good thermal insulation and relatively good fire resistance performance. Besides, aluminium composite inhibits propagation of electromagnetic radiation and thus, it is being used in the environments where radiation is emitted for example airports, military installations, computer centres and hospitals.
Timber is a good choice of cladding material. This is because it offer design freedom, a wide range of products and ease of handling. The design of cladding using timber as the material is flexible. It can be designed according to the environment and fit into any site with a minimum expenses. They can be designed to look traditional, modern or unique which able to suit the style and imagination of the owner.
Besides, timber has natural resilience which gives a good building flexibility which able to resist stresses and strains that caused by the foundation movement, wind storms or seismic movement. In addition, timber has good control of sound. It has the natural sound damping properties which can keep noise out of buildings and can reduce the reflected noise and absorb airborne sound from one side to the other.
Moreover, timber offer excellent thermal performance throughout the year and the timber is an economical comfort material. When there is difference between the temperature inside and outside the building, the heat will be transferred through walls, floors, windows and doors. The heat is transferred through the timber cladding walls by the movement of air within the cavities, as the radiant heat through cavities and direct conduction through the solid materials of the wall.
In addition, timber has different durability according to the types of timber used. Timber is environmentally friendly because it is renewable, reusable and biodegradable. However, certain types of timber need chemical preservatives to increase their service time. There are several reasons causing timber deteriorates, the main cause is the fungal decay where the moisture content within timbers exceed 20%.
The heartwood of timbers such as Western red cedar, European Oak, European Larch and Douglas fir ,can be classified as durable and moderately durable which do not need preservative treatment for external wall cladding. Meanwhile, for the timber which is classified as slightly durable required preservative treatment. The examples of timber requiring treatment are Spruce, Fir, Pine and European Whitewood.
Besides giving the timber preservative treatment to increase its service life span, there are also others ways to enhance the durability by reducing the risk of wetting and removing moisture instantly. It can be done through protecting the timber cladding from rainwater with large eaves overhangs, ensuring the timber cladding is not directly contact with porous materials and including a well ventilated and drained cavity behind the cladding which at least 19mm wide.
Question 2: Describe two types of subsurface drainage system for domestic usage.
Subsurface drainage system for domestic usage
Subsurface drainage systems are usually used in areas where soil will not drain quickly on its own. It is used to remove excess water from the soil. This system commonly have to deal with foul water or surface water. The sources of foul water is from kitchen waste, bidet, toilet or soil and vent pipe and any industrial process. For the sources of surface water , the surface water is channeled through rainwater pickups, yard or roard gullies or linear drains at gardens or road sides.
The subsurface drainage system for domestic usage consists of underground pipe line and manhole. The underground pipe line is responsible to channeling the sewage and storm water while the manhole is responsible for channeling the sewage only.
Underground pipe line
The underground pipe line can be referred as drainage and sewer pipes underneath the ground. The pipes are made from a range of different materials such as uPVC, concrete, cast iron , high density polyethylene(HDPE) and asbestos. There are two types of jointing for underground pipe line. Firstly, for the plain ended pipes, they are having identical ends and thus are joined by means of a coupling. Secondly, the socketed pipes have easily identified 'male' and 'female' ends and therefore, it must be laid with the 'female' end pointing upstream in order to ensure the jointing is tight enough.
The construction method of underground pipe line can be simplified into a flow of sequence. In the construction process, it is important to ensure the pipes is laid in straight line from the required point to point with a fall so that the sewage or storm water can be flow using the gradient created or by gravity. Firstly, excavation of trench should be allowed in order to provide working space and bedding around the pipes. Any trench which is deeper than 4 feet has to be properly shored up. Then, there are two types of bedding required to protect the pipes from ruptures or breakages depending on the pipes materials. For rigid pipes such as clayware require two layers of bedding made up of selected fill where there is no stones over 40mm, no lumps of clay over 100mm and no organic or frozen material, and granular material. For flexible pipes such as plastic pipes, three layers of bedding are required. They are selected fill, selected fill or granular material and granular material with 10mm single size.
Next, the pipes will be laid in straight line to a steady gradient. A taut string line, sight rails or laser line will be used to ensure the accuracy of the alignment and level of the pipes. The bedding is prepared first, with a recess scooped out to accommodate sockets. The minimum gradients for foul water drainage is 1:40 while for surface water is 1:100.
After that, the installation of fittings and access points will be carried out. They are being installed at the head of run, at the bend or change of direction, at the location where there is change in pipe diameter and junctions.
Manholes or inspection chambers
Manholes are designed in order to allow a man to enter and the inspection chamber should be situated to make lengths of drain accessible for maintenance. The very basic of use of manholes and inspection chambers are to contain the foul water under good working conditions and to prevent and resist the entry of groundwater and rainwater. The suitable size of them should be enough to permit the access for inspection and cleansing. They should also have a durable, suitable and removable non-ventilating cover, consists of step irons or ladder where the depth requires this and suitable benching when there are open channels.
The construction of manholes and inspection chambers can be constructed through several ways, such as in brickwork, in situ concrete, precast concrete, cast iron, glass fibre reinforced polyester and vitrified clay.
For the manholes made in brick, they are normally built of 215 mm walls in English bond with class B engineering bricks to cement mortar. It shall be finished fair face internally as the internal rendering may be fail and causes blockages. For the inspection chambers which are located in granular soils above the water table with depth not exceeding 900mm may be built in half brick walls. The chambers are normally roofed with a precast or in situ reinforced concrete cover slab with 125 or 150 mm thick. Brick manholes are specially suitable for shallow depths and offer considerable flexibility in design.
For the manholes which are made of in situ concrete, they have walls with thickness not less than that of brickwork manholes. This form of construction of manholes is not used widely even though it could be particularly advantageous for irregularly shaped shallow manholes with large diameter pipes.
For the precast concrete manholes and inspection chambers, as the materials are precast in the factories, thus, they enable fast construction and usually built in circular sections or rings which may be connected with ogee joints or rebated joints sealed with cement mortar. Step irons are already been built in the precast concrete manholes.
For the cast iron manholes, they are formed from bolted cast iron sections to be used in bad ground or cast iron access chambers for the use in buildings. However, the cost is very high. For the plastic manholes and inspection chambers, these are available moulded in thermoplastic and thermosetting materials such as polypropylene, glass fibre reinforced polyester, either as the integral bases or as complete chamber units.
Lastly, for the inspection chambers made of vitrified clay, they have integral base provides a variety of inlet and outlet connection positions. There are flexible joints incorporating elastomeric sealing rings, connect raising pieces to the base and allow for different depth.
Question 3: Briefly describe the function of road and pavement.
Functions of road and pavement
The construction of road and pavement should be only carried out after all the services, ducts and drainage system are completely installed. Pavement can be described as the surface of the road while road is the part which including the pavement and the related road accessories such as kerbs and pedestrian walkway. The more detailed description of pavement is it is a surface which is used on purpose for the traffic to be operated safely and economically.
The road can be classified into three groups at the simplest level according to the road functions, which are traffic flow routes, distributor roads and access roads.
For the roads with flow function, it means to enable efficient throughput of long distance motorized traffic. It can be further explained that all of the express roads and motorways and some urban ring roads are having the flow function. The number of access and exit points provided is limited.
For the roads with an area distributor function, it is said to have the function which allows the accessibility through and from areas such as residential areas, industrial areas, recreational areas and rural settlements which have scattered population. There will be junctions for traffic exchange and road sections between the junctions to facilitate the flowing of the traffic.
For the roads with an access function, there is actual access to the buildings along the road. Both the junctions and the road sections between them are for traffic exchange where the public can have better accessibility to the building along the street or road. Thus, it increases the level of convenience of the public.
The functions of pavement is to provide a flat surface for the wheeled vehicles to travel comfortably. Besides, the soil of the road will be protected by an overlay of imported or treated material. Thus, the transportation load onto the ground can be transfer and distribute widely throughout the road. This is done in order to limit and reduce the stress of the traffic passing through on and in the ground. Therefore, the service life of the road can be increased.
In addition, the function of road and pavement is also to avoid and prevent the ground surface of road from being damage by the weathering effects. The weathering effects are caused by several weathering agents which are rainwater, wind and storm.
Question 4: Cellular concrete roofing units, pavement overlays, bridge decks, airport runways, pressure vessels, blast resistant structures, tunnel linings and ship-hull construction are some application of a particular fibre reinforced concrete. Specify the type of the fibre with characteristics comparison with the conventional concrete.
Comparison between Steel Fibre Reinforced Concrete and Conventional Concrete
Steel fibre reinforced concrete is a composite materials which is made with Portland cement, aggregate and incorporating discrete discontinuous steel fibre. Meanwhile, the conventional concrete is a composite material which consists of cement, water,and coarse or fine aggregates such as limestone or granite and sand .
The steel fibre reinforced concrete has great crack resistant. This is due to the discontinuous steel fibre play an important role in the concrete as it will provide bridge across the cracks. Thus, it provides post-cracking ductility. When the steel fibre are strongly bonded to the material with sufficient amount, it will enable the steel fibre reinforced concrete to carry significant stresses in the post-cracking stage. Therefore, we can say that the strength and toughness of concrete is increased. On the other hand, the conventional concrete is a brittle material with characteristics such as low tensile strength and low strain capacity.
Besides the steel fibre reinforced concrete is able to arrest cracks, it thus posses better tensile strength and increased extensibility. This tensile strength can be seen when at the first crack and under flexural loading, this is successfully achieved because the steel fibre has the ability to hold the materials together even after extensive cracking. The steel fibre reinforced concrete has the energy absorption characteristics and the great ability to withstand repeatedly applied, shock or impact loading. This is a characteristic where ordinary conventional concrete unable to perform. This is because the conventional concrete has low tensile strength, relatively low elasticity at low level of stress and posses a very low coefficient of thermal expansion.
In addition, the use of the steel fibre reinforced concrete can increase the impact and abrasion resistant thus it also has longer durability and the maintenance costs is reduced. Besides reduced maintenance costs, the cost for secondary reinforcement mesh for the ground supported slabs is also waived due to the use of steel fibre reinforced concrete. Moreover, there is no crack control steel mesh required which leads to there are no need to purchase and store any additional material. For the conventional concrete, there are cast in situ concrete or precast concrete. If the cast in situ concrete is used in the construction site, thus, there will be a need to purchase the materials such as cement, sand and admixtures so that the formation of concrete can be done on site. There is also a need to purchase reinforcement such as reinforced bar, links and stirrups. As a result, there is also a need to get a place for the materials to be properly stored so that no wastage or lost of materials happened.
In addition, the construction time can be shortened due to there is no need to lay mesh and spacers when using steel fibre reinforced concrete. Therefore, no delays can be caused due to fast track schedule and the position for jointing is easier when using steel fibre reinforced concrete. Besides , the number of workers such as semi-skilled and skilled workers can be reduced on the construction site due to there is no need of cutting and handling of steel reinforcement. This is then sufficiently reduced the project costs. For the conventional concrete, the number of labours needed is higher and the time taken for the completion of project is longer. This is because there is a need to cut and handle the steel reinforcement on site and thus the labours cost is higher. And there is also higher material cost due to transportation cost, storage, unloading cost of the steel reinforcements and as a result it increases the total project cost.
As the steel fibre reinforced concrete able to control cracking which occurs at the hardened stage, it also has even distribution of fibres throughout the concrete and a tougher surface with fewer bleed holes. It is thus enhanced the load bearing capability and improved the flexural properties while it also able to reduce the absorption of water and chemicals. Therefore, steel fibre reinforced concrete is widely used in places such as heavy duty flooring applications including internal and external areas and civil engineering applications such as airport runways, pressure vessels, tunnel linings and blast resistance structures.