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CONSTRUCTION FORMWORK AND FALSEWORK

1.0 INTRODUCTION

The construction of a concrete building requires formwork to support the slabs (Horizontal Formwork) as well as columns and walls ( Vertical Formwork ). Formwork is the contact surface and structural backing needed to contain fresh concrete until it can safely support itself. If it is not removed, it is called permanent formwork. If it has to be supported from below, the structural support is called falsework.

The exact distinction between formwork and falsework is not very important, but it is usual to call all material and equipment used to cast walls formwork. This is because the system of loads is self-contained, while for concrete members such as slabs or beams, falsework is used to take the loads to the ground below or to a similar support. For such members, the actual surface material and its immediate support is considered to be formwork.

Typically, formwork will be found in the context of a construction contract. The designer and the engineer will provide the contractor with details of the concrete work which is to be constructed, but will provide no information on how this is to be achieved. It is the contractor’s expertise which the client is buying. The contractor will study the shape of the structure to be created, and decide on appropriate methods to construct it. If the complexity and quality are both minimal, it may be left to a competent formwork carpenter. However, it is likely today that the design will be more scientific. This may be by formal structural design and detailing, so that the personnel on the site have precise guidance on what to do, or it may be that a formwork supplier will be called in and asked to propose methods and to supply the equipment needed. A main contractor may sublet the activity of the formwork to a specialist subcontractor, who would then take the responsibility for this aspect of the work.

The person who actually puts up the formwork will normally be a carpenter or joiner by trade. Many such workers have served a traditional apprenticeship, but today more and more people come into this job by other routes, with less effective training. They may be expected to operate without any guidance, or at the other extreme they may be provided with drawings which set out how to deal with every detail. Some training is available from the Construction Industry Development Board Malaysia ( CIBD ). Courses on design are available from some colleges, but it is fairly specialised subject and they are few and far between. The CIBD conducts examinations on formwork design at a trade level.

Formwork molds the concrete to the desired shape and size, and controls its position and alignment. Concrete forms are engineered structures that are required to support loads such as fresh concrete, construction materials, equipment, workers, various impacts and sometimes wind. Formwork system development has paralleled the growth of concrete

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construction throughout the twentieth century. As concrete has come of age and been assigned in creasingly significant structural tasks, formwork builders have had to keep pace. Form designers and builders are becoming increasingly aware of the need to keep abreast of technological advancements in other materials fields in order to develop creative innovations that are required to maintain quality and economy in the face of new formwork challenges.

Formwork was once built in place, used once, and subsequently wrecked. The trend today, however, is toward increasing prefabrication, assembly in large units, erection by mechanical means, and continuing reuse of forms. These development are in keeping with the increasing mechanization of production in construction sites and other fields.

Due to the globalization and the development of the world, the construction is increasing from day to day. Every concrete construction needs formworks. The principal requirements for concrete formwork are that it be safe, produce the desired shape and surface texture, and being economical. Besides that, it is a necessity to ensure that the materials should not pollute and harm the environment. Unfortunately, the traditional timber formwork has lead to some past and current technology and environmental impacts. Hence, other materials that can overcome the problems brought by timber should be chosen for formworks construction. It is to ensure the best quality of concrete and environmental friendly.

The usual design of formwork is for wall, slab, column, and beam. There are several types of formwork; timber, steel, aluminium and plastic formwork. The most preferred formwork is timber and steel. Therefore we are just focusing only in timber and steel formwork. This report is cover the past and current related technology including recommending steps that need to be taken in order to reduce environmental impacts from its activities. Brief information on timber and steel formworks is as stated below;

Timber Formwork:

The conventional wood system is sometimes referred to as the stick form or hand-over-hand method. Conventional wood system includes formwork for slabs, beams and foundations. The system is generally built of lumber or a combination of lumber and plywood or moisture-resistant particleboard. Formwork pieces are made and erected in situ. For stripping, conventional wood systems are stripped piece by piece, then cleaned. It is easy to produce but time-consuming for larger structures, and the plywood facing has a relatively short lifespan. It is still used extensively where the labour costs are lower than the costs for procuring re-usable formwork. It is also the most flexible type of formwork, so even where other systems are in use, complicated sections may use it.

Steel Formwork:

The conventional steel system is sometimes referred to as “ an improved stick system” It is made out of prefabricated modules with steel frames. It is now widely used in this industry especially for high cost construction. Steel formwork also produced good

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surfacing on the hard concrete. These types of formwork are easy to install and also easy to dismantled. It can be used for a long period because it is made out of the material that is not affected by the environment. It is also can reduced the wastage due to its properties. Steel formwork can also be produced according to the desirable size and shape, because it is made earlier in the factory. Due to its weight, tower crane and large mobile crane should be able for handling of steel formwork.

Figure 1: Formwork and Falsework

Figure 2 : Falsework

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2.0 LITERATURE REVIEW

2.1 Timber Formwork:

Timber is the most basic material. It is relatively cheap and easy to shape as required. Equally, it is easily cut up and reduced in size, eventually becoming waste. It is easy to fix inserts and the like on the inside of a form face for casting into concrete; it is relatively light in weight for handling, but it is of limited durability. An introduction to timber for structural use is given in the BSI Code of Practice for Falsework. Note that timber on site for formwork always has to be classified ad wet.

Timber is also the basic of a number of sheet materials. Generally, timber or wood formwork is made by putting together members of selected timber that have been cut into several different shapes. These include plywood, blockboard, chipboard, boards made from wood flakes ( oriented strand board and waterboard and hardboard or hardwood which density more than 880kg/m3 such as ‘Cengal’ and ‘Balau’. Long ago plywood was unsuitable for formwork, because the glue which held the veneers together failed in damp site conditions, but nowadays almost all glues are sufficiently durable. Outer veneers should be sanded and without holes normally referred to as solid. The choice was relate to the quality of the concrete surface required.

For boards which consist of timber particles bonded with a matrix of plastic glue, the low stiffness of this glue leads to a board which is less stiff than plywood or solid timber of the same thickness. The quality of the concrete surface produced from such boards may not be smooth enough, and the deterioration of such surfaces can be fairly rapid. Because the boards are cheaper, however, there are applications where they prove useful. Before the installation of the members of formwork, some criteria should be put into considerations. The crucial criteria that counts are as follow;

a) Shape of members b) Correct position c) Correct angles for batters etc. d) Line and level e) Accuracy within permitted tolerances f) Finishing heights (mark off) g) Verticality (plumb)

Other criteria that should also be taken into consideration are the jointing of the members. The joint of formwork must be flush and tight, nails should not protrude into the concrete. The water stops should be correctly positioned and fixed suitably supported by the formwork. The formwork is built on site out of timber and plywood or moisture resistant particleboard. It is easy to produce but time consuming for larger structures, and the plywood facing has a relatively short lifespan. It is still used extensively where the labour

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costs are lower than the costs for procuring re-usable formwork. After commencing with traditional plywood and timber formwork, it was found that there was a panel formwork on the market which proved to be much more economical and faster. We are especially urged to remember that today’s modern formwork is tomorrow’s traditional formwork and new methods and systems must continually be found to improve formwork in the future.

Figure 2 : Timber Formwork

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2.2 Steel Formwork:

Steel can be used both as sheet material for the face of formwork and as hot or cold-formed sections, used to form the support or framing. It is much more successfully fabricated in a shop. It is a heavy material, and thus the cost of handling it is likely to be greater, as it has to be dismantled into small pieces. Pieces are connected either by nuts and bolts, or often in proprietary systems by some more ingenious time saving device. With both methods, pieces are liable to be lost all too easily. Steel sections are used in the fabrication of different formwork components, namely:

1) Steel panel forms. 2) Horizontal and vertical shores. 3) Steel pan and dome components used for joist and waffle slab. 4) Steel pipes for formwork bracing.

Steel formwork is made by fabricating the steel into selected sizes and shape. Steel formwork may be classified in a general way as follows;

1) Unit forms of various standard sizes for the assembly of slab, beam, wall and column forms.

2) Purpose made the steel forms to specific shapes and sizes 3) Supports or units of falsework for strutting, bracing, backing, and propping various

steel. Steel formwork is made by shaping liquefy steel into various shape. The most common shape of steel formwork is as slab, beam, wall, and column.

For the manufacturing of slab formwork;

The typical maximum span indicated is based on a 150 mm slab. For the trapezoidal sections, the usual size permitting a simple or multiple span of

1.5 to 3.8m for 1.2mm sheet thickness. And for trapezoidal section designed for use in slim floor systems permit spans of

up to 6.5m unpropped and 9m propped. Also for re-entrant sections permitting a simple or multiple span of 2.0 to 5.5m for

1.2mm sheet thickness.

For the manufacturing of beam formwork;

The beams are cast with the floor slab there are two basic possibilities of carrying out of the formwork which beams are not too large and beams are large.

The spacing of the beams is relatively close, the beam formwork can include half of the slab formwork so that no further formwork is necessary.

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Went beam formwork is constructed in one piece it will be necessary to form the sides of the beam with a pitch or inclination of 10%.

Normally there have many sizes of beam such as 500 x 800mm, 700 x 800mm, 300 x 400mm, and 600 x 900mm.

For the manufacturing of wall formwork;

The wall panels are combined with the slab panels so that the wall and slabs can be formed monolithically in one casting operation,

And the number of joints between panels is minimized so that there is less chance of grout leakage or an uneven surface finish at the joint, which is a common fault with in traditional timber formwork.

For the manufacturing of column formwork;

The manufactured systems which may be assembled for different column sizes and heights. One of these is for circular columns consisting of stove-enamelled steel or aluminium mould segment which are connected with other aluminium mouldings having an elastic sealing, in a former.

These segments are made in two designs, one for column from 300 to 900mm in diameter with variation in formwork size of 25mm steps.

Other for column from 900 to 2000mm where the formwork size can be varied in steps of 50mm.

The manufacturers claim that steel or aluminium formwork can be used as many as 250 times.

But normally the manufacturing of column and beam formwork, the panels are moulded into the required sizes. The sizes are ought to be moulded according to the standard whether it is British Standard, Euro Code, or Malaysia Code.

Figure 4 : Steel Formwork

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2.3 Strength and Durability of Formwork :

Formwork for concrete must support all vertical loads that maybe applied until the loads can be carried by the concrete structure itself (George R. White & others, 1975). Strength and durability is important, it is frequently stiffness which is the controlling factor in the design. This is of direct importance to the flatness or straightness of the concrete. It should be sufficiently rigid under construction loads to maintain the designed shape of concrete. Besides that, it must be stable and strong enough to maintain large members in alignment. The formwork should be strong enough its own weight and the concrete weight. Other lateral forces caused by dumping of concrete, movement of construction equipment and action of wind must be resisted by formwork to prevent lateral failure. It becomes more crucial to big mass concrete construction. The forms must support all the applied loads without collapse or excessive deflection.

Timber formwork such as plywood is classified as interior or exterior. The classification is made on the basis of the resistance of the glue bond to moisture, which is affected by the adhesive used, the veneer grade, and the panel construction. Plywood is made in four exposure durability classifications: Exterior, Exposure 1, IMAGE (Exposure 2), and Interior. Exterior type is made with 100 percent waterproof glue. For greatest strength and stiffness, plywood should be installed with the face of grain perpendicular to the supports. Section properties parallel to the face grain of the plywood are based on panel construction which gives minimum values in this direction. Properties perpendicular to the face grain are based on a usually different panel construction, which gives minimum values in that direction.

Steel formwork is very durable if it is in thick form. But if it is in the sheet form, it will also dent if it is too thin. It can be used infinitely with the minimum maintenances. The maintenances are such as handling the forms carefully when erecting and stripping or moving the formworks. Besides that, the formworks should be clean and treat so that the concrete will not adhere to the formworks. They can be reused over 100 times meanwhile traditional timber formwork can be only used for 8-15 times (C.S. Poon, 2007). A set of steel formwork can be used to complete a building construction and might still be able to be used in other projects. It also very strong and able to sustain high load of concrete hence it is very suitable to be used when high stress occurs. They are more rigid and less possibility to formwork strength failure which may lead to formwork collapse. Furthermore, steel formwork frames are stronger and less susceptible to damage. But, steel formworks are very heavy and difficult to handle. Some large steel formworks might need crane to be transported at site.

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2.4 Formworks Materials Effects on Construction Duration:

Construction duration is defined as the rate in which concrete building is raised and can be expressed in terms of number of floors erected per week or months. Construction duration is an important criterion in a project. Shorter construction is normally preferred by both client and construction contractor as long construction time will lead to losses. Formwork operations can control the pace of construction projects. Formwork is typically supported by several levels of shores and reshores that carry the loads until the concrete gains enough strength to support its own weight and all other externally applied loads. As a result, several floors may be blocked, preventing the progress of any other construction activities. Faster formwork cycle from erection to stripping would allow for faster removal of shoring and reshoring and faster overall project progress.

Robert L. P. and Garold D. O. (1995) stated that, “Cellular-steel panels are frequently used for the forms and structural unit of floor systems. This system offers a numbers of advantages, including lightweight, the elimination of shores and form of concrete, rapid of construction and abundant raceways for utility services.”

The timber formworks are erected on site by fastening the framing lumber and sheathing materials such as plywood using spreaders and fasteners. As timber has a limitation of sizes, normally a formwork is built up of many pieces of lumber. Hence, it is time consuming to construct the timber formworks especially for complicated or large structures.

Steel formwork has a high efficiency and workability. This is because of steel formworks can be erected easily using modular systems clip, screw or bolts and nuts. Therefore, by using steel formwork, faster track construction can be achieved as construction duration of a project can be reduced.

Time for construction should not be wasted in formwork construction as it is a temporary structure. Besides that, delay of formworks will also postpone the work of concrete thus, lengthen the completion time of a project. Hence, suitable of formwork should be used to chosen for a project to shorten the project completion time.

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2.5 Quality Of Concrete Regarding To Formwork Materials:

The quality of the resulting concrete is dictated by the quality of formwork materials and workmanship. Many concrete related problems such as discoloration, stains, and dusting are attributed to concrete formwork. Also, some deformed concrete surface are due to deformed formwork systems caused by repetitive reuse and inadequate support of formwork. “The quality of surface finish of concrete is affected by the formwork materials used”. (George R. White & others, 1975).

The materials used will determine the perfection of concrete surface. Formwork materials must be impermeable to ensure the perfection of the concrete surface and the finished concrete shape will not be altered. To ensure the high quality of concrete, materials which are impermeable, have smooth surfaces and will not easily shrink or swell should be used to construction formwork. This is to ensure the water tightness and regularities of formwork so that the concrete produced will have smooth surfaces, even colour, and correct dimension and shape of concrete.

Unfortunately, timber which is a common formwork material is a porous material which can absorb water. The porosity of the timber is various and thus leading to variable degree of concretes’ mix water absorption. This might cause noticeably differences of colour tone in the stripped concrete surface, which are lighter and darker patches. As timber will absorb bleed water from the concrete surface and retain in the cell cavity, the moisture content of the timber formwork will increase subsequently with the time of the formworks are reused. If unpigmented plain concrete is used, the differential moisture content of timber formwork will cause a distinct variation in shade of the stripped concrete from dark on initial pours, to light on subsequent pours. Other than that, a mixture of old and new timber as formwork materials very often accentuates uneven colour of concrete surface. Besides that, timber has organic substances such as lignin which can result in discolouration of the concrete. This will cause the uneven colour of the concrete and affect the aesthetics of the concrete surface (Jack Cleaver, 2007).

Good quality, straight stock is need for timber formwork to ensure the perfection of concrete cast. A layer of mould oil should be applied to the inside surface of formwork to reduce the uneven colour of concrete. But, mould oil will increase the risk of blow holes. Blow holes are small holes, of less than 15mm in diameter, caused by air being trapped between the formwork and concrete face (R. Chudley, 1999).

Furthermore, as timber formworks are erected from pieces of timber; it is difficult to ensure that the joints are water tightness. Besides that, if the timber formwork is dry, it will absorb the moisture from wet concrete and swell and bulge thus give an unwanted profile for the finished concrete. On the other hand, if timber with high moisture content is used, it will shrink and cup which will cause the open joints. If the joints do not have water tightness, the mortar will leak and results in the disfigurement of the concrete such as honeycombing. Moreover, common defect in timber such as bow, crook and twist caused by improper drying

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will cause the inability of formwork to provide a proper alignment or smooth and straight surface for concreting and finally result in uneven concrete surface or concrete disfigurement. Plastering is need for levelling the uneven concrete surface before applying the floor finishes such as tiles and paints. If the leakage is serious, it might properly affect the strength of concrete.

Steel can provide a strong, impermeable, large and uniform formwork. As the steel formwork is cast in the factory, it has a precise and accurate specification. It will have the exact shape and dimension of the specific concrete product. Thus, better quality concrete products which meet the original concrete design will be produced by steel formworks. Besides that, it has only few joints as steel formwork can be mould in a longer span and larger panel. Hence, it can ensure the water tightness of formwork. Furthermore, the surface of steel formwork is smooth. The concrete surfaces obtained by using steel are suitable for applying tiles and paints directly (C.S. Poon, 2007). But, a very smooth surface produced by steel formwork might also will bring problems for process concrete finishing.

To make sure the quality, materials and equipment should be checked on arrival to make sure they are what is required by the designer. They should be examined for reduction of section or deterioration, particularly if they have been previously used. It should be ensured that components, such as pins, are to the manufacturer’s specification. All materials and items of equipment should be checked to ensure that they are in the intended place, and of the proper type. Material may be of the wrong grade or incorrect cross-section. Dimensions should be checked, to ensure that the form is in the right place and spacings are not too great. It is important that all connections are done up tightly, so that any movement is minimal and leakage is kept under control.

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2.6 Formwork Labour Forces:

Labour forces are needed in every construction activities. No matter how good is the materials, planning, programming, design, and supervision, if the labour forces are not good, then everything is in vain. For this reason there is a need for more labour forces who have been trained in the use of formwork plant and are not just men who can use a hammer. Therefore workers can be divided in skilled workers and general workers. Skilled workers are needed for special skill tasks and they are paid higher than general workers. The labour forces needed influence the construction project cost. The project cost increases with the needs of labour forces.

The construction of timber formworks is complicated and time consuming. Labour is needed intensively for the erecting works such as cutting the timber and fastening the framing lumber, sheathing materials, bracing and others. Skilled workers are needed to erect the formwork and mould the formwork shapes in order to ensure the quality of formwork. Other than that, many unskilled workers are needed for the general works such as timber cutting. Besides that, the striking process is difficult because the timber formwork has a lot of joints as it is made up of many pieces of lumber. Furthermore, the timber formwork members are usually hand-lifted from floor to floor at site for multi-storey construction. Therefore, labour is needed intensively.

The self-raising forms are prefabricated and remain connected until the top of the building is reached. This reduces the need to assemble and disassemble the forms after each lift. With the use of built in hydraulic rams to raise the formwork system, the requirements for crane time and crane attendants is greatly reduced. Craning operations are only needed to initially place the formwork system and to disassemble the system once the forming is complete. This allows the crane to be used elsewhere on the job site, thus possibly increasing productivity elsewhere since the crane is rarely needed with the self-raising forms.

Steel formwork is a prefabricated formwork system which is cast in the factory. When the formwork arrived at sites, it is properly cut in required size and shape. Besides that, it has specially designed formwork accessories such as ties, brackets and bracing hardware. The steel formwork frame is designed so that the panels can be easily and quickly fastened and unfastened. It can be handled as one unit. It requires only labour force for erecting, striking and re-erecting the formwork. Sometimes, crane is used to aid the formwork erection. Hence, it requires less labour forces.

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2.7 Formwork Economy:

Formwork is the largest cost component for a typical multistory reinforced concrete building. Formwork cost accounts for 40 to 60 percent of the cost of the concrete frame and for approximately 10 percent of the total building cost. “Formwork may account for 40% to 60% of the cost of concrete construction, it is essential that the formwork plan be carefully developed and evaluated” (S. W. Nunnally, 2007). Therefore, materials of formwork should be chosen thoroughly to minimize that cost. Pie chart 1a and pie chart 1b present a breakdown of different cost categories for conventional concrete slab and wall formwork. A large proportion of the cost of conventional formwork is related to formwork labour costs. Significant cost saving could be achieved by reducing labour costs.

Timber is an economical material of formworks construction but it has a short life span. As the reusability of timber formwork is low and it can only be reused 8-15 times, several sets of timber formworks are needed for a high-rise building or a large project (C.S. Poon, 2007). Hence, the cost of the formwork is high in long run. This is a waste of money for a construction project as formwork is only a temporary structure for a building. Furthermore, regarding to the concrete disfigurement of concrete problems caused by timber formworks, more plastering is needed to level the irregularities and thus it again increase the cost of a construction project.

Steel formworks might have the high cost at the beginning of the construction but as steel formwork has a long lifespan and high reusability; it can save the cost in long run. This is because less replacement of old formwork is needed. It can save concrete volume needed because it can form a long span comparing to timber formwork. Steel formwork slashes construction costs where can saves on all the key components of the floor - concrete, labour, and the supporting of the structure because lower preparatory costs , fewer temporary props, less site congestion and fast track construction. Moreover, the waste steel can be sold for recycling. The steel is molten and made in another product. This can not only increase the income of construction contractor but also reducing the construction waste (C.S. Poon, 2007).

(C. K. Austin 1978) also stated that steel forms are very durable where one set of steel formwork can be used to complete a project, and then reused for another project or scrapped for recycling. Steel forms can produce a better quality concrete finish when compared with timber forms. Although their initial cost is higher, they can be cheaper in the long run, particularly with their recycling potential.

Therefore, reuse of concrete formwork is a key for economic formwork construction. After only five reuses, formwork materials costs drop to 40 percent of the initial cost. Formwork elements must be handled with care and should not be dropped. After repairing, cleaning, and oiling, the used formwork elements should either be stockpiled for future use or reused in other areas. Before reusing formwork elements, they should be inspected for

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damage. Defects on the inside face must be repaired or removed; otherwise they will reflect on the finished surface of the concrete to show the same defect.

21%

28%38%

10%

3%

Pie chart 1a : Distribution of costs for cast-in-situ concrete slab

Concrete

Reinforcing

Formwork Labour

formwork Materials

Concrete Placing

52%

30%

11%

7%

Pie chart 1b : Distribution of costs for cast-in-situ concrete wall

Formwork Labour

Concrete Materials

Formwork Materials

Concrete Labour

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2.8 Formwork Maintenance:

When the formwork is struck, it should be cleaned and inspected for damage. For timber and plywood formwork, repair may consist of fixing pieces which are coming apart by re-nailing, perhaps replacing a damaged member, or replacing the facing material. If it is desired to repair the face sheeting, this can be done with a plastic filler, or in more major cases by infilling with another piece of plywood, a job for a good joiner. The use of a filler will only be successful if the timber is cut back far enough such that the mould oil has not penetrated; otherwise it would be impossible for the filler to get a good hold. Such a filler will almost invariably show on the concrete, owing to its different absorbency.

Formwork of timber and plywood can normally be dismantled, and if the state of the materials is good enough, they can be used again. It is most undesirable to leave timber with nails projecting. If these timbers are to be burnt, the nails should be bent over on dismantling; if not, they should be removed. The more thoroughly formwork has been constructed, the more difficult it will be to get it apart for further use.

If the equipment is of steel, site maintenance will be much less practicable. The forms can be cleaned, but it is not easy to remove dents, and the welding of broken parts will prove difficult. They should be returned to a metalworking shop which has adequate facilities. With proprietary equipment in particular it is difficult to judge the grade of steel, and welding techniques must relate to the original steel used to be successful.

Renovation of aluminium alloy members is even more difficult, and apart from straightening minor bends at corners, it is impracticable to do anything on site. Much plastic formwork is unmendable on site, and it is really only GRP which can be effectively repaired. This can be done by using car body techniques, but the comment about getting rid of the mould oil first is equally important here.

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2.9 Construction Waste:

Construction waste is becoming a serious environmental problem in many cities around the world. ( Chen,2002; Ferguson, 1995; Shen,2002; Smallwood,2000; Wong and Tanner, 1997). Construction and demolition ( C&D) debris frequently makes up 10-30% of the waste received at many landfill sites around the world ( Fishhein,1998). Construction and demolition ( C&D ) waste according to the EUWaste strategy is considered as one of the ‘priority’ waste streams. According to the sixth Environment Action Program entitled ‘Environment 2010: our future, our choice’, recommendation actions need to be taken with respect to the stream of C & D waste, ( EC,2001 ).

In Malaysia, 16,000 tonnes of solid waste produced in the country every day. There are about 230 landfills in Malaysia and an estimated three times as many illegal dumps. 80% of the landfills have an estimated remaining lifetime of only 2 Years (Agamuthu, 2003). In Malaysia, the construction industry generates a lot of construction waste which may cause significant damage to our environment. Waste minimisation and effective and sustainable waste management is thus a most pressing issue nowadays. Waste is defined as the by-product generated and remove from construction, renovation and demolition workplaces or sites of building and civil engineering structure. ( Cheung, 1993 ). Solid waste is defined as those wastes from human and animal activities. Wastes accepted by public authorities for ultimate disposal, including hazardous wastes, liquid-solid sludge from industry and water / waste water plants are within this definition. Solid waste can be classified as municipal waste ( e.g. paper, plastics, food wastes, ashes, and special wastes such as street sweepings, dead animals etc), industrial waste ( e.g. timber, demolition and construction waste, treatment plant waste, hazardous waste (e.g. radioactive substances, chemicals, biological waste, flammable waste, explosives etc) ( Kiely, 1997).

Constructions activities are increasing rapidly in the world due to development. Sadly, the construction industry has become the main source for the waste in the world. Construction waste can accounted for more than 50% of the waste deposited in a landfill (J. Ferguson, 1995). The increasing of construction wastes generation has caused significant impacts to the environment and become a pressing issue in the community. The impact of construction is both on economic and the environment. The wastes will take extra time and resources such as money and transportation for disposal that in increase the cost burden of construction firm or may slow down the construction progress. Besides that, if the waste was not disposal properly, it will cause pollution to the environment. “Unless these wastes were recycled, illegal dumping into valleys, rivers and drains will continue to cause pollution and environmental problems (Mayin M., 2006).

The majority of material waste in construction is formwork. Timber board is a common material that is used for formwork. The wastage is often caused by natural deterioration results from usage and cutting waste which are difficult to avoid. A construction site might be bearing wastage of 20% in timber used for foundation works (Tam,

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2002). Another material waste is concrete. The contractor might not estimate the accurate volume of concrete due to improper planning and finally caused over ordering or preparing of concrete. Steel reinforcement is also a material waste as cutting of steel bar will always produces waste. Lastly, masonry work is another waste generator in construction as bricks and blocks are the most common walling materials. The cutting of brick for certain size is the main cause of waste. Besides that, the broken damage of fragile bricks due to unpacked supply will also further increase the waste.

In order to minimize the construction waste generation, the materials needed should be estimated accurately or reused in construction industry if possible. Waste minimization requires careful planning, creative problem solving, changes in attitude, capital investment and a genuine commitment. However, it can save substantial amount of money through more efficient use of valuable resources and lower costs for waste treatment and disposal. Besides that, materials that can is durable and can be reused should be chosen as construction materials. As formwork which one of the main waste contributor in the construction industry, a properly selection of the type and materials for formwork should be done. The formwork should be durable, can be reused for many times. Materials that can be chosen are such as steel as it can be reused over 100 times according to C.S. Poon from Hong Kong Polytechnic University. Another solution for construction waste problem is recycling. The economic and environmental benefits to be gained from waste minimization and recycling are enormous. The possibilities of selling some of the waste materials make the removal of waste from site being no charge or can earn some extra money.

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2.10 Deforestation:

Deforestation is the conversion of forested areas to non-forest land use such as arable land, pasture, urban use, logged area, or wasteland. About half of the mature tropical forests, between 750 to 800 million hectares in the world have been fallen. The growing worldwide demand for timber and land for commercial and industrial development has lead to deforestation. Timber is a common material for most of the concrete construction. But it is not durable and only has a short lifespan. Hence, a lots of timber is needed for the timber formwork and thus timber formwork has become an important contributor to deforestation.

Furthermore, deforestation enhances the greenhouse effect and contributes to the global warming as it increases the amount of carbon dioxide (CO2) in the atmosphere. From 1850 to 1990, deforestation worldwide released 122 billion metric tons of carbon into the atmosphere, with the current rate being approximately 1.6 billion metric tons per year (Anonymous, 2007). The increasing of CO2 caused by deforestation will further increase the global temperature.

Worldwide, 5 to 80 million species of plants and animals comprise the "biodiversity" of planet Earth (Anonymous, 2007). Rain forest is the main habitat of those plants and animals. Many of the rain forest plants and animals can only be found in small areas, because they require a special environment in which to live. This makes them very vulnerable to deforestation. If their environment is destroyed, they might become extinct. Species are disappearing from the tropical rain forests as they are cleared.

Hence, the usage of timber should be reduced in order the save the forest in the world. Besides that, the reforestation and better forest management should be done to solve the problems. Materials other than timber should be use in construction.

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3.0 DISCUSSION

Formwork systems are one of the key factors that govern the success of a construction project in terms of speed, quality, cost and safety of works. Nowadays, most projects are required by the client to complete at the shortest time possible as a means to minimize cost of capital. For buildings of high-rise nature, the most effective way to expedite works is to achieve a very short floor cycle, that is, to have the structure of a typical floor completed in the shortest time. The key to achieve this, again, from the production point of views, is by the use of a set of efficient, appropriately designed formwork. Modern buildings in many occasions can be very complex, either in terms of scale or size of the building, no matter they are high-rise or horizontally spread, or in terms of architectural or structural design, or to fit for sophisticated building services or other facilities requirements. The design and use of the right formwork system, as well as the stipulation of an effective resource planning strategy to control and maximize the use of the formwork, are again crucial to the overall success of a project.

As we know that traditional timber formwork has lead to technology and environmental impacts from its activities, thus steel formwork is being introduced to reduce those weaknesses of traditional timber formwork. Steel has been an important material for the fabrication of both common and special purpose formwork. These are some advantages of steel formworks can both benefits in construction technology and environmental impacts from its activities.

Firstly, as we know that the material of steel formwork has a very high durability and strength. Steel formwork is more durable and has longer lifespan as it is stronger, less susceptible to damage and sturdier than timber formwork. Beside that, steel formwork provides adequate rigidity and strength so that it can sustain any load and movement without failure where it can be erected, moved and re-erected rapidly, disassembled, and provided suitable handling equipment is available for the large sections. Steel formwork also can sustain the big concrete mass comparing to timber formwork therefore it is suitable use in heavy construction. A set of steel formwork can be used to complete a building construction and might still be able to be used in other projects. Steel formwork also can be reused many times more than traditional timber formwork. Thus, it is more worth to use steel formwork for large and repetitive construction.

Besides that, steel formwork also has a high workability and efficiency. Steel formwork system can be erected twice faster than timber formwork system. This is because of steel formworks can be erected easily using modular systems clip or screw. Since, traditional timber formwork is time consuming and tedious to be erected as timber formwork are formed using many small pieces of wood and timber panels. In short, by using steel formwork, construction time of a project can be reduced because of fast track construction went use steel formwork.

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Moreover, steel formworks can produce a better quality concrete products. The steel formwork concrete products will have less disfigurement and irregularities comparing to concrete products of timber formworks. Normally, the steel formworks mould are made in factory, it will follow exactly the design specification. As a result the dimension and alignment accuracy of the concrete products will be assured. The concrete products of steel formwork will be smooth and are suitable to apply concrete finishes such as paints and tiles directly. As well as, the problem of uneven colour of concrete surface caused by the permeability of timber formwork will be reduce by using the steel formwork because steel is impermeable materials. Because of that no plastering is needed for levelling the uneven surface of concrete caused by imperfection of formwork.

Furthermore, steel formwork required less labour force for erecting, re-erecting, and striking the formwork. This is because steel formwork was in frame designed thereby the panels can be quickly and easily for fastened and unfastened. It can be handled as one unit and then steel formworks mould are made in factory. On the contrary, both the skilled and unskilled labour is needed intensively for do the timber formwork jobs such as cutting the wood or timber and forming the formworks on site. Therefore, comparing to traditional timber formworks, the steel formworks require much lesser of labour force for erecting, re-erecting, and striking the formworks. .

Even though, steel formwork might have the high initial cost in the construction project comparing to traditional timber formwork. But on the other hand steel formwork really can save the cost in long run. This is due to steel formwork has a high reusability and long lifespan. Likewise, the wasted steel formwork can be sold for recycling. This can not only reduce the waste disposal of formwork but also can increase the income of construction contractor by sold steel formwork for recycling. Besides that, waste steel are scrapped for recycling which less construction waste are produced. The wastage produce by steel are slashes into small amount. Moreover, the recycling of steel can both benefits the environment and contractors as they can earn some extra money from recycling of steel. Steel formwork application help reducing the problem which help to solve the construction waste problem which is so serious nowadays

Metal of steel is material which is iron that obtained from the nature. However, it only contributes very little or none deforestation or loss of biodiversity comparing to using the materials of timber. Even though metal mining might sometimes cause deforestation but the amount is very little if comparing to logging for timber formworks. The materials of steel is very durable and having a high reusability, hence not much metal mining is needed for steel formwork. Thus, it can reduce the deforestation and the biodiversity will be preserved. It follows that can then help to reduce the greenhouse effects and the degree of global warming.

In addition, steel formwork moulds can produce any desired concrete shapes as they are cast in the factory. The concrete steel formwork mould cast will be having the exact

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shape and dimension like in order or required and then steel formworks are suitable for any simple shape of concrete moulding from common rectangular shape to circular, ellipse and curved surfaced concrete products, thus steel formwork is a good choice. Steel formworks can produce concrete with correct dimension and smooth surface which is exactly like the designed concrete. But steel formwork is preferable for large areas of work with standard sizes and simple shape. However for smaller, irregular sizes, complex surface and mould designs timber is more economical.

Normally after the timber formwork was used and cannot be used again for the next timber formwork construct, the timber are usually burn by the person in charge and this contribute to pollution of environment such as air pollution that can cause serious health problems for children, pregnant women, and people with respiratory problems. But, if we use steel formwork can be reused for many times and recycle when it cannot be used anymore which the steel is melted and used for other application. Hence, less open burning will happen at site as no timber waste will be produced by steel formwork. Therefore, this can help to preserve the human health and environment.

The falsework is that part of formwork which supports the forms. In civil engineering, the heights and weights encountered are normally in excess of standard propping facilities and some form of scaffolding is used. Three basic types of scaffold which can be employed in falsework:

1) Scaffold tubes and fittings. 2) Prefabricated systems. 3) Specially designed falsework in the form of prefabricated units.

The first two types were initially designed for the access scaffolding market but have been used increasingly for falsework. The third type prefabricated tubular units is available from any the formwork and scaffolding specialists.

The advantages and disadvantages units used are depends on types of the falsework. Tube and fittings used as falsework provide the most versatile material available although unlikely to be the most economic meaning the labour in erecting and dismantling is very high compared with unit systems. Prefabricated systems initially designed for simple access scaffolding have made a great impact on the falsework market. The systems usually consist of vertical frames, which are linked together by a patent bracing system; this form of linking can be visually inspected to ensure stability whereas normal tube fittings cannot be checked by the same method. Proprietary systems of decking including telescopic beams or prefabricated beam are often linked with falsework systems. The prefabricated systems therefore offer simplicity of erection coupled with a built- in grit, which give high control of components spacing. Prefabricated falsework are made from larger diameter tube and are capable of carrying heavier loads than the normal scaffold units. These systems are used

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extensively for supporting bridges and other heavy structure, which require variable falsework. Typical falsework structure such as super- slim soldier and erection of scaffolding falsework

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4.0 SUMMARY

There is no simple, ready-available solution for most formwork situations for complex buildings, especially when the construction is to be done in a fast-track manner, like most of the projects in overseas. Due to the problems brought by traditional timber formwork, steel formworks has been introduced to be its solution of in both the technology and environmental impacts. Steel formwork brings a lot of advantages in the past and current technology of concrete forming comparing to traditional timber formworks.

After the discussion, we know that steel formworks can produce a better quality concrete finish comparing to timber formworks. Besides that, the steel formwork is suitable for any simple shapes such as rectangular and circular shape of concrete products. Steel formwork also has a high strength and durability. It can be reused much more times if compare with traditional timber formwork. Moreover, steel formwork has a high workability and efficiency. Steel formwork can be erected twice faster than timber formwork system. Although steel formwork initial cost is higher, it can be cheaper in the long run, particularly with its recycling potential and high reusability. The important was less labour force is needed for steel formwork construction.

Furthermore, steel formwork is more environmental friendly. Because steel formwork does not lead to the deforestation thus the biodiversity will be preserved. Hence, less open burning will happen at site if we just only use steel formwork. Besides that, as waste steel can be scrapped for recycling, thus less construction waste are produced. The problem of pollution due to improper management of construction will also can be eliminated.

In addition, about the falsework actually was any temporary structure used to support permanent structure while it is not self-supporting. Falsework is used to take the loads to the ground below or to a similar support. The important of falsework is often not fully appreciated and there is a tendency for civil engineering contractors to underprice this work in their tenders and as a result of this, design standards and construction are apt to suffer. If falsework subsequently collapse, permanent work might be damaged and worker injured or killed. Therefore the contractor must aware and use BS 5975:1982 is the code of practice which gives recommendations for the design and use of falsework on construction sites. For guidance on the design and use of access scaffolding and special scaffold structures other than falsework, reference should be made to BS 5973.

As a conclusion, steel formwork is a high performance in past and current technology and also environmental friendly material for formwork construction. The usage of timber in formwork construction should be reduced or replaced by other materials such as steel formwork or aluminium formwork. About the advantages and disadvantages units used are depends on types of the falsework. Therefore, the other falsework methods and other

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materials that have more advantage should also be researched in order to make the environmental impacts to the minimum while optimizing the formwork performance.

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5.0 REFERENCES

1) American Institute of Architects, ( AIA 1997). “Environmental Resource Guide”. John Wiley & Sons, New York.

2) Agamuthu, P. (2001). Solid Waste: Principles and Management. Institute of Biological Sciences, University of Malaya.

3) Anonymous (2007). http://sacass.edu (accessed on 2nd Aug, 2007) 4) Awad S.Hanna. (1999) Concrete Formwork System. University of Wisconsin-Madison,

Madison, Wisconsin, New York. 5) Bossink, B.A.G. and H.J.H. Brouwers. (1996) “Construction Waste: Quantification and

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13) J. Ferguson (1995). Managing and Minimizing Construction Waste: A Practical Guide 14) Michael P.Hurst (1983). Formwork. Construction Press, London and New York. 15) M.Mayin (2006).Recycle Wood, Construction Waste. The Star Newspaper. (3rd October,

2006) 16) R. Chudley (1999). Construction Technology. Addison Wesley 17) Robert L. Peurifoy and Gerold D. Oberlender. Formwork for Concrete Structure, Third

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