There are some elementary objectives of the cladding system. These objectives are the reasons for the invention and adoption of cladding system due to our increasing construction technology and demands of clients. There are many types of clients, some are emphasize more on aesthetic value, some are emphasize more on functional value, some are emphasize on time of erection and even some are emphasize on construction cost. So, the primary objectives of cladding system can be concluded as below:
Supply of enclosure to the structure with the function of essential protection against the natural elements such as wind, rain, storm and etc.
Invention and adoption of dry construction method which is more advanced such as off-site prefabrication, off-site manufacturing and etc.
Minimize the additional dead load onto the frame.
Improve the aesthetic value of the structure or the architectural concept.
Control internal environment.
Thus, in order to accomplish these elementary objectives of cladding system, the cladding system must perform these functional requirements:
Strength and Stability
It should have sufficient strength to support its own weight between the points of support or fixings to the structure.
It must provide adequate stability against lateral wind pressure.
It is essential to allow the differential movement in material expansion and contraction between the cladding system, the structural frame and the adjacent building elements.
Exclusion of Wind and Rain
Generally, the method is to construct solid cladding systems with an outer leaf as a rain screen and inner leaf of light weight block for insulation.
In order to accommodate movement and resist weather deterioration, the material that used to seal joints and claddings must be resilient enough.
Durability and Freedom of Maintenance
The frequency and extent of work necessary to maintain minimum functional requirements & acceptable appearance must be minimized to save cost.
There are some problems and requirements of maintenance of several types of material. These are some examples. For masonry, a little maintenance is needed only. Glass requires frequent cleaning and renewal of seal. Besides that, sheet materials such as bronze, aluminium and stainless steel will be oxidized easily and faded faster as compare to masonry and glass.
Control of Internal Temperatures
As we know, the solar is gained through glass panel. Thus, we must control the proportion of glazed to ‘solid’ areas.
Besides that, thermal control can also be achieved by some methods. For example, deep recessed window used in conjunction with external vertical fins and used of non-transparent external louvres. By the way, used of special solar control glass is encouraged also.
Thermal Properties
Additional insulation need to be provided by lining of the cladding materials.
It must achieve the U-values that laid down in the building regulations
It must avoid the problems that would arise from ‘cold bridging’ and from surface and interstitial condensation.
The problem of air leakage should be minimized.
Environmental and Sustainability Issues
It is defined as how much the cladding system can contribute to the overall energy efficiency of the building.
Environmental friendliness of cladding materials also plays a very important role in these issues.
Fire Requirements
Due to the proximity of other buildings and the use class of the building, fire resistance may be required.
In order to restrict the fire from spread over the internal and external surfaces and within voids, the lining material that used for insulation is made up of non-combustible materials.
Sound Insulation
The resilient pad is used to prevent sound originating within the structure to be transferred vertically through the cladding members.
Airborne sound originating from external source can be prevented by utilizing double glazing panel to window area.
Aesthetic Issues
The context within which the building is situated will determine the level of aesthetic of that building.
Necessary to satisfy the aesthetic aspiration of the clients.
General Function of the Building
There are some functions of building that need to be stated and established such as day lighting and natural ventilation requirements, degree of privacy required, exploitation of pleasant views or exclusion of undesirable views and etc.
A CLIENT REQUIRES A ROAD THAT REQUIRES LITTLE MAINTENANCE WITH REASONABLE NON-SKID PROPERTIES. WITH THE AID OF DIAGRAMME, SUGGEST A TYPE OF ROAD AND THE CONSTRUCTION METHODOLOGY FOR THE PROPOSED ROAD.
The road that I will proposed which meets the demand of client is rigid pavement. Rigid pavement is made up of concrete road slab. These are some functions of pavement. Pavement provides a flat surface that makes the journey comfort. Pavement helps to transfer and distribute the transportation load onto the ground evenly. Besides that, pavement protects ground surface against weather effects such rain and wind. These are the characteristics of rigid pavement.
Characteristics
Rigid pavement
Subsidence damage
Considerable with expansion joints
Initial cost
High and require low skill labour
Maintenance
Low
Appearance
Glare from sun
Non skid properties
Reasonable
Resistance to wear
Good if the quality of concrete is controlled
Ease of reinstatement
Costly, difficult, require curing time
Weakness
The requirement of relatively frequently spaced temperature expansion and contraction joints, which also provides a less comfortable surface for riding.
Construction Methodology
The construction methodology of rigid pavement can be classified into several procedures which are placement, screeding, consolidation, finishing, curing and joints.
Placement
Truck or truck attachment is used to place the precast concrete directly to the desired position. Otherwise, placement machine is used for more accurate and even placement. Once the precast concrete has been unloaded from the truck, it tends to become less homogenous.
Figure 1 Figure 2
Screeding
During this process, the excess part of the roughly placed precast concrete is cut off to the desired elevation of slab. Generally, this is done by dragging a straightedge across the slab at the required elevation.
Consolidation
In this process, the freshly placed precast concrete is making to form a more uniform and compact mass. This can be done by eliminating unwanted air voids and causing it to move around potential obstruction such as reinforcement bar. Generally, consolidation is done by using vibrators which are formed by long and slender vibration rods. Vibrators can be drive by rotating an eccentric weight which causes the whole vibrator to move back and forth. Vibrators are used to excite particles within precast concrete mass. This will cause the particles attach each other closer and better flow around obstructions. Proper consolidation is very important to the performance of rigid pavement. It must possess adequate vibrations to enhance the durability. Too much or too little vibration will lower the performance of rigid pavement. Vibrator static head also influences the efficiency.
Figure 3
Finishing
In this process, the task is to create the final surface finish and texture of fresh precast concrete. In general, finishing can be categorized into 2 types which are floating and texturing. In floating, a flat surface is run across the precast concrete in number of times and may involve many different tools. This process is used to remove high spots, low spots and imperfections, embed larger aggregate particles beneath the surface and to prepare the surface of mortar for texturing with compaction. After floating, fresh precast concrete is quite smooth. A rough pattern is usually formed by dragging a broom, rough-textured item, or tinted instrument across the surface to enhance the non-skip property of rigid pavement. In general, texturing can be divided into 2 types which are Microtexture and Macrotexture. Microtexture is more common than Macrotexture. Microtexture is accomplished by dragging a section of burlap or artificial turf behind the paver.
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Curing
The task of this process refers to the maintenance of adequate moisture and temperature within a precast concrete mass as it sets and hardens in order to develop the desired properties of strength, durability and density. Curing can be done by 2 different methods which are water curing and sealed curing. Water curing is method that prevents moisture loss and supply additional water to precast concrete surface. This method is labour intensive and generally not practices in rigid pavement anymore. Sealed method is method that prevents moisture loss but do not supply any additional water. This can be done by putting a waterproof covering over a slab such as plastic or using a liquid membrane-forming chemical compound.
Figure 4 (Finishing) Figure 5 (Curing)
Joints
There are many types of joints used in rigid pavement. The basics of transverse contraction joint construction should include joint location, saw cutting timing, saw cutting depth and joint sealing. Joint locations are necessary to indicate on the construction plans and should be planned in advance. The timing of contraction joint sawing is determined by 2 main factors which are shrinkage cracking and precast concrete support strength and joint raveling. In the aspect of saw cutting depth, transverse contraction joints are usually cut to a depth of 1/4 to 1/3 of the total slab depth in order to make sure cracking only occurs at the joints. After the previous procedure has been done, it requires to be sealed to reduce the water and incompressible material entry.
Figure 6 (Joint Layout) Figure 7 (Shrinkage Crack) Figure 8 (Sawcut Depth)
DESCRIBE THE PERFORMANCE AND SPECIFY THE MATERIAL THAT CAN BE USED TO FILL THE VOID OF DISUSED STRUCTURES, EG: CULVERTS, REDUNDANT SEWERS, CELLARS AND BASEMENTS AND ALSO FOR SOIL STRUCTURAL STABILIZATION, EG: BRIDGE ABUTMENTS, TUNNEL STABILIZATION AND EMBANKMENTS.
In our construction technology, there are many materials that can be used and performed very well in construction process such as concrete, plastic, stone, ceramic and timber. All of these materials possess advantages and disadvantages. In this question, the material that will be chosen is aerated concrete.
There are a lot of reasons why I choose this material, aerated concrete. Aerated concrete is a highly workable and low density material which incorporating entrained air up to 50 percents. In general, it has the characteristics of self-levelling, self-compacting and may be pumped. Besides that, the risk of plastic shrinkage or settlement cracking of aerated concrete is significantly lower as compared to normal concrete. This foamed concrete is ideal for filling up the redundant or unnecessary voids such as disused fuel tanks, sewer systems, pipelines and culverts. Other than that, aerated concrete also has a good thermal insulation property.
The aerated concrete can be fully utilized in several applications such as:
Unwanted voids
Pipelines
Service ducts and shafts
Bridge arches or subways
Disused structures
Culverts
Redundant sewers
Cellars and basements
Higher structural stabilization
Bridge abutments
Tunnel stabilization
enbankments
Insulating fill
Low density insulating sub-screed
Insulating fill to house over-sites
By the way, there are several highlighted final concrete performances of aerated concrete that can said to be the advantages of this kind of concrete. Aerated concrete contains high entrained air content. With this property, the aerated concrete is able to resist the damage that formed from freeze and thaw. Besides that, entrained air can acts as a good thermal and acoustic insulator. The aerated concrete has good cohesion ability. It can form a stable foam structure that reduces settlement and reduces bleeding and segregation. Other than that, aerated concrete possess controlled density and strength. For example, low strength of concrete enables the removal for subsequent access to services and maintenance. The range of densities and strengths available depends on the types of foamed concrete. Structure that formed by aerated concrete is very stable. It can generally be surfaced after 24 hours.
Besides that, other materials can be combined together and included in the mix. Combination of different materials depends on the applications and requirements. There are some combinations such as polypropylene fiber, fibersteel, quarry fines, vermiculite, flyash and volcanic ash. Autoclaved aerated concrete is one common type of aerated concrete. It is a material like wood but without the disadvantages of combustibility, decay and termite damage. The initial cost of autoclaved aerated concrete is very high but it can be compensated by lower cost of labour, finish, maintenance, and energy. In terms of manufacturing issue, construction issue and etc, it is a good ecological choice. The autoclaved aerated concrete is very versatile because the mixture proportions can be modify to setup different insulation values and compressive strength. Due to the reason of autoclaved aerated concrete is light in weight and workable, thus it can reduce the construction time, waste and energy by faster speed of construction.
BRIEFLY DESCRIBE THE ACTIVITES INVOLVED IN EXTERNAL WORKS AT THE START OF THE CONTRACT.
In general, external works is defined as the construction works that done externally from the main building. The external works can be divided into several main parts which are drainage requirements, temporary constructions, public utilities, special industries services, minor external buildings, security and lighting. In construction industry, most of the activities are spanned within the entire project period but some of the external works are involved at the start of the contract. These external works are drainage main runs, access arrangement, storage facilities, car parks, hard areas for plants and machineries for construction of foundation and service mains to building entry.
Firstly, drainage will be explained in detail. Drainage can be divided into 2 main types which are surface drainage and sub-surface drainage. Surface drainage is defined as the removal and disposal of water from the surface of a pavement. Sub-surface drainage is the type of drainage that uses the underground pipes and other fittings to direct the flow of water from where it is not wanted to some other places. Sub-surface drainage might include land drainage. Land drainage can be defined as removing and disposing of surplus groundwater gardens, fields and other plots of open land.
Surface drainage system often refers as channels that direct the surface water to a drainage outlet. These channels are made up of stone or precast concrete. This system usually discharges all the relatively clean water into a local watercourse such as ditch, stream or river. This system can reduce the demand on the effluent treatment plant. The relatively clean water usually consists of water from the roof and the paving. The channels are slope down towards the public footpath and highway. After that, the water will be directed into gullies or linear drain which will flow to the storm water sewers later.
In surface drainage system, the gully and access point is function to collect and discharge the collected water into local watercourse. Generally, there are three types of gully and access point used to perform this function. They are individual trapped gully, continuous grating over precast channels and combined kerb and drainage system.
In the aspect of individual trapped gully, there are many types of gully that have been used. P-trap and hopper is commonly used with rainwater pick-ups rather than use in large areas drainage of paving. Yard gully also know as a bottle gully, compact gully or an universal gully. Other than that, road gully is much larger than P-trap and yard gully but they work in the same way. The specifications of road gully are it has a fixed 150mm diameter outlet but come in a variety of diameters and depths. For example, road gully the used within the carriage ways is commonly used to drain an area less than 250m2.
In the aspect of continuous grating over precast channels, it can be various sizes, from 50mm deep units for roof drainage to 250mm deep for motorway drains. These channels can made up of various materials such as polymer concrete, wet-press concrete, HDPE and stainless steel. In a specific application, the type of channels used will depends on the end use of the drain. There are two main types which are built-in fall units and regular depth units. Built-in fall units are channels that maintain a fixed depth along their whole length and compulsory laid to a fall. It is suitable to use in large drainage for flat areas such as car parks, freight yards, airports and etc. The regular depth units are suitable to use in short length drainage which has a natural gradient. Lastly, the combined kerb and drainage system have 2 main functions. It can acts as road isolator. Besides that, it is also a discharge point of collected surface water.
Generally, sub-surface drainage system deals with foul water such as kitchen waste, toilet or soil and vent pipes, bath or shower or bidet and any industrial process. Besides that, this system can deals with both foul water and surface water such as rain water pick-ups, yard or road gullies and linear drains. Sub-surface drainage system consists of underground pipe line, manhole or inspection chamber and culvert. In underground pipe line, various materials can be used to make pipes such as vitrified clay, uPVC, concrete, ductile and cast iron (CI), glassfibre reinforced plastics (GRP), high density polyethylene (HDPE), pitch fibre and asbestos.
In general, there are 3 main types of pipes which are socketed clayware, plain-end clay and plastic 100/150mm. There are 2 main types of jointing of pipes. Plain ended pipes are a type of pipes that have identical ends. They can be joined by means of a coupling. Other than that, socketed pipes have identifiable ‘male’ and ‘female’ ends. The method of laid must be in the way of ‘female’ end pointing upstream.
Next, access chambers are commonly not more than 600mm deep which provides an easy access for cursory inspection and access of maintenance equipments. Inspection chamber possess the same function as the access chamber but inspection chamber is larger than access chamber with a minimum 450mm diameter. Besides that, inspection chamber tend to have more branches or spurs feeding into them. Normally, the inspection chamber can be up to 1000mm deep. Manhole is the largest chamber that provides the same function. Manhole can be any depth with the minimum internal dimension of 600x900mm. There are two main types of manhole which are brick manhole and precast concrete manhole. After that, culvert can be defined as a structure which provides a waterway or other opening under a road. In general, the type of pipe culvert chosen should be class Z spun reinforced concrete with spun concrete collars or spigot and socket type.
At the start of the contract, there are some external works that need to be done in order to proceed to start the construction works. The external works that need to be done 1st is to prepare and provide hard access to all parts of the site, hard storage for materials, site facilities and car parks. Generally, in order to reduce the cost of temporary road and access, the contractor will lay the base course of the future permanent road as the temporary road and access. There is a way to keep the site temporary road dry for the convenience of construction works which is laying the drainage system as soon as possible. Public utilities services are very important to a building. Thus, all the public utilities need to be planned carefully before any major structures are built. Any constructions of service mains and ducts should be constructed concurrently with the foundation construction works in order to make the entire construction works faster and avoid any inconveniences.
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