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The materials for cladding are often chosen for their manufacturing parameters, cost, durability as well as appearance. Examples of the materials are metal cladding and precast concrete cladding. Both of these differ in terms of strength, durability and cost of each material.
The durability of a metal cladding is affected by type of material, exposure of the panel, local environment factors, corrosion protection as well as the details of the cladding itself. When using metal cladding, the lifespan of this system is generally defined in terms of its period from the first use to the first maintenance which is the period for when then material may need to be repainted to maintain its original appearance or the original coating system can no longer protects the metal underneath. Usually, metal cladding suppliers will provide detailed information regarding their product including the durability of the metal cladding itself. The coatings of cladding are also affected by the intensity of the exposure to ultraviolet radiation which means less longevity but for organic coated steels, the period to the first maintenance can be as long as 30 years. The durability of a metal cladding can also be affected by the workmanship related defects during the installation process such as scratching the coating.
Since metal cladding began to be used in a range wider than simply industrial buildings, then architectural features for aesthetical value such as curved eaves and corners as well as horizontal profiles have been developed. Texture and colours are mixed to form a more interesting cladding rather than a plain metal cladding but the incorporation of architectural features requires huge care over specifications as well as installations. The most used cladding system for architectural purposes are profiled cladding and composite panels which were often laid horizontally and fixed to vertical sub-frames of the building itself. A curved profile panels are produces from flat profiled sheets, either by creating a series of cross ribs that were then adjusted onto the metal locally. The other method in producing curved profile panels involves stretching the profile to provide a smooth curve without cross ribs like the earlier method but this method is more restricted in the range of curves and radii available to be used. For this curved profiled panels, a more careful setting out is needed compared than the flat profiles but it has the advantage in being stiffer than the flat ones. From this, it is obvious that a curved profiled panels and composite profiled panels are more durable yet stronger compared to flat profiled panels. Besides, this can be used as an advantage for architectural purposes which the world often look for nowadays.
Precast Concrete Cladding
Precast concrete has now become the architectural cladding material of choice because it has the advantage in terms of aesthetics, durability, low maintenance surface, applied finishes, as well as construction economy. This system often combines the benefits of low maintenance, high durability, excellent fire resistant and even energy efficiency. This combination makes precast concrete cladding an ideal solution for the emphasis of prestige, luxury and aesthetic appeal, especially for high rise offices and residential towers or for economy and durability priority such as in lower rise offices and commercial structures. Brick, marble, tile and granite are of typical finishes used for precast concrete cladding but any other decorative stone can also be applied for more variations. This type of cladding system is one of the most cost effective because it is naturally coloured.
The main advantage of precast concrete cladding are in terms of installation, where the installation for this cladding system is swift and rapid; the sized of the panels which are typically sized so that they can span grid to grid, allowing a large area of the applied building to be weathered as quickly as possible. Besides, there are no scaffolding required in the installation of this precast concrete system as all fixings are accessed from the rear end of the panels. Sometimes, for construction that needed to use glazing units and insulation, they can easily be fitted to the precast unit in the factory that made the precast unit itself, thus decreasing the time needed for the work. But, in order to make precast concrete cladding system more cost effective, it is important that panel sizes to be maximized and a degree of repetition exists which these will ensure a number of panels can be casted from a single mould.
Question 1b: Describe two types of sub surface drainage system for domestic usage
In building a good drainage system, there are few principles that need to be followed. Some of them are:
Material should have adequate strength and durability.
Every part of a drain should be accessible for the purpose of inspection and cleansing.
Drains should be in straight run as far as possible.
Drains must be laid to a gradient which will render them efficient. The fall or gradient should be calculated according to the rate of flow, velocity required, and the diameter of the drain.
Every drain inlet should be trapped to prevent the entry of foul air into the building which the minimum seal required is 50mm.
For domestic usage, there are three types of subsurface drainage system which are combined system, separate system and partially separate system. The scheme or plan layout of drains will depend upon factors such as number of discharge points, relative position of discharge point, and drainage system of the Local Authority sewers.
In a combined system, all the drains are discharged into a common or combined sewer. It is the most simple and economic method since there is no duplication of drains. This system has the advantage in terms of easy maintenance. Besides, all drains are flushed when it rains and it is impossible for this system to be connected to the wrong sewer. But this system also has its disadvantage, which is that all the discharges should pass through the sewage treatment installation, which might be costly and prove to be difficult with periods of heavy rain.
A separate system in domestic subsoil drainage is the most common method applied by the Local Authorities where two sewers are used in this method. One of the sewers receives the surface water discharged and conveys them direct to a suitable outfall such as a river or sea, where the discharges require no treatment while the second sewer receives all the soil or foul discharges such as from baths, basins, sinks, showers as well as toilets. These discharges will then being conveyed to the sewage treatment installations. In this system, more drains are required and it is often necessary to cross drains one over another. There is a risk of connecting the drain to a wrong sewer and the soil drains are not flushed during heavy rain, but the savings on the treatment of a smaller volume of discharge leads to an overall economy which is acceptable to be applied in domestic area.
Question 1c: Briefly describe the function of road and pavement
A road is an identifiable route, way or path between two places which might or might not be available for the use by public. Public roads, especially those major roads that connect two destinations are defined as highways. A modern road normally smoothed and paved to allow easy travel of road users. While pavement is defined as surfaces intended for traffic and soil, which are protected by an overlay of imported or treated material with the objective to limit the stress in the ground. The surface of road as well as its associated construction is known as pavement.
One of the main functions of roads and pavements is to transfer and distribute transportation load onto the ground. Even on the ground soil itself we can use to travel, but the loads of the transportations that use the path is not evenly distributed since the soil is not compacted and supported. With roads and pavements, the loads of the transportations were equally distributed and this provides a safe and comfy journey.
The second function of road and pavement is to provide a flat surface. This is to achieve a comfortable, smooth and safe journey. A smooth riding surface is important for riding comfort and throughout the road development; this has become the measure of how road users see of a road. A rough surfaced road can be caused from few factors; one of it is caused from pavement distress due to structural deformation.
Besides, the other major factor of road and pavement is to prevent the subgrade from being damaged. Subgrade is the supporting soil underneath the pavement. It is important to protect the subgrade as it is the foundation for the road and pavement. Like building, if the foundation is damaged, the whole pavement is damaged as well. If the subgrade is over-stressed, it will deform and lose its ability to properly support the loads above it. So, the pavement should have sufficient structural capacity in terms of strength and thickness, to adequately reduce the stress so that the loads and stress do not exceed the strength and capacity of the subgrade. The thickness and strength can vary depending on the combination of subgrade types as well as loading condition.
Roads and pavements are also used to provide adequate surface friction or in other words, roads and pavements are to provide a skid resistance surface. The priority in road user requirement is that of safety. Every road user concerns about their safety when using roads. Safety, especially in wet conditions such as during heavy rains, can be linked to a loss of surface friction between the tyre and the pavement surface due to the existence of water surface on the road itself. So it is obvious that roads and pavements should be able to provide an adequate skid resistance for road users, in any weather conditions.
The last function of roads and pavements is to provide a waterproof layer. The outer surface of a pavement acts as a waterproof surface which prevents the subgrade that supports the pavement from becoming saturated because of water absorption. When they become saturated, the soil loses its ability to support the applied loads, let alone overload, and this will lead to a premature failure of the pavement itself. So, the outer layer should not contain even a tiny pore, in order to prevent water from being absorbed underneath.
Question 1d: Cellular concrete roofing units, pavement overlays, bridge decks airport runways, pressure vessels, blast-resistant structures, tunnel linings and ship-hull construction are some applications of a particular fiber reinforcement concrete. Specify the types of the fibers with characteristics comparison with the conventional concrete.
Fiber reinforced concrete can be defined as a composite material which consists of a mixture of cement, mortar or concrete and discontinuous and uniformly dispersed suitable fibers. The addition of this fiber would act as crack arrester as well as improving its static and dynamic properties. Fiber reinforced concrete is used as it has the advantages of static and dynamic tensile strength, energy absorbing characteristics and an improvised fatigue strength. The main factor that affects its properties is the relative fiber matrix stiffness where the modulus of elasticity of matrix helped in stress transfer efficiently. A good bond is important to improve the tensile strength of the material.
There are many applications with different types of fibers and these were affected by the characteristics of the certain fiber containing in the concrete:
Glass Fiber Reinforced Concrete (GFPC)
Glass fiber reinforced concretes are mainly used in exterior building panels or as an architectural precast concrete. One of the advantages of GFPC is that they are lightweight. Despite their light weight, a GFPC panel is strong and is more environmental friendly as they were mostly made of recycled post-consumer glass.
Steel Fiber Reinforced Concrete (SFRC)
Steel fiber reinforced concrete is a composite material made of hydraulic cements, water, fine and coarse aggregate and a dispersion of small, discontinuous steel fibers. The steel fibers are distributed uniformly throughout the concrete matrix which gives the SFRC the ability to control temperature and shrinkage cracks. They were commonly used in cellular concrete roofing unit.
Polypropylene Fiber reinforced Concrete (PFRC)
Polypropylene fiber reinforced concrete has the ability to improve freeze-thaw resistance, improve resistance to explosive in case of severe fire, and improves impact resistance. It is often used in foundation piles, pre-stressed piles and facing panels.
Asbestos Fiber Reinforced Concrete (AFRC)
Asbestos fiber reinforced concrete has been used since early 1900s which were applied into concrete. Unfortunately, this composite became a concern as it is venomous to health but AFRC were still used in some applications which is outside of health zone such as in pipes and sewer pipes.
Mica Flakes Fiber Reinforced Concrete (MFRC)
This type of fiber reinforced concrete partially replaces asbestos applications in cement boards, concrete pipes and repair materials. Mica flakes as fibers can help preventing long-term decreases in terms of tensile strength as well as impact strength.
Carbon Fiber Reinforced Concrete (CFRC)
Carbon fiber reinforced concrete is an electric conductor concrete and by this, they are normally used in locations where electrical contacts are necessary. Besides, it has the characteristic of corrosion resistance, compared to other metallic electrical contact materials.
Fiber Reinforced Concrete (FRC)
Conventional Reinforced Concrete
Protect steel from corrosion
Steel prone to corrosion
Lighter (in terms of materials)
Heavier (in terms of materials)
Greater strength (per 1mÂ³)
Weaker (per 1mÂ³)
Table: Characteristic comparison between FRC and conventional concrete
The above table shows the characteristic comparisons between fiber reinforced concrete and conventional concrete. in terms of durability, FRC is more durable compared to conventional concrete this is because of the presence of fibers in FRC that adds to the durability of the concrete and thus, making it more flexible to be used widely in construction.
Besides, the weight of FRC is relatively lighter compared to conventional concrete. Such as for Glass Fiber Reinforced Concrete, both the glass and concrete make up the volume and thus decreasing the weight as the fiber contained in the concrete has lower mass compared to a full conventional concrete. This superb characteristic increases the workability of the FRC, beating conventional concrete in terms of weight as well as workability. The workability of a FRC will reduce if the fiber volume is increased. Therefore, the volume of fiber need to be controlled but this is an advantage as the cost for materials will not be that high. the workability of FRC can be measured by conducting a Vebe test.
Unfortunately, a fiber reinforced concrete is more expensive as it is needed to be readily made in factories, so does the material costs which need to make up for the materials for fiber. But, from the table, it is obvious that FRC has more advantage over conventional concrete, despite the costs. So, this higher cost for sure will increase the reliability of the material, and the building itself.