BACHELOR OF ENGINEERING (HONS) CIVILEC220 Course : Construction Technology (ECM 576) Title of Experiment : Formwork Group Number : EC220 7A1 List of Members in Group: No. Name Student ID 1 NUR ANISHA BINTI MOHD ISA 2014601394 2 NUR MAHIZAN BINTI AMMINUDIN 2014882972 3 NURUL AFIFAH BINTI FAUZI 2014645202 4 RUQAYYAH BINTI RASHID 2014441846 TABLE OF CONTENT No. Content Page 1.1 The Purpose of Formwork 1-2 1.2 General Design of Formwork 3 1.3 General Formwork Requirement 4 1.4 Material for Formwork 5 - 12 1.5 Surface treatment 13 - 15 1.6 Defect 16 1.7 Common Failure of Formwork 17 1.8 Causes of Failure 18 1.9 Types of Formwork 19 - 24 1.10 Case Study 26 - 28 1.0 FORMWORK 1.1 THE PURPOSE OF FORMWORK Formwork is a mould or box into which wet concrete can be poured and compacted so that it will flow and finally set to the inner profile of the box or mould. The purpose of this formwork is to contain freshly placed and compacted concrete until it has gained enough strength to be self-supporting. Formwork should be designed to withstand all expected loads include the self- weight, weight of reinforcement, weight of wet concrete and wind loads. It is must be sufficient to prevent deflection under loading otherwise it will undergo deformation. Furthermore, the formwork uses to produce a concrete member of the required shape and size. If the formwork design are not proper or does not follow the requirements, then it will break when the concrete is placed. There also various formwork shape that design based on horizontal system and vertical system. Formworks for horizontal system are beams and slabs and also formwork for vertical system are walls and column. Horizontal formwork is subjects to vertical loads which are to be carried off to solid subsoils through formwork bearers and main bearers as well as columns. The example of vertical loads are produced by persons and working tools. The vertical formwork system exerts lateral pressure of the concrete mix. This depends on the factors of concrete placing technology and also composition and properties of concrete mix. The formworks also use to produce the desired finish to the concrete. The appearance of the concrete is very importance so care is taken with the surface of the form. It is necessary that all steel particles are removed as they will rust and spoil the final appearance of the concrete. To reduce the incidence of blowholes from striking of the formwork, the surface 1 of the form must be coated with release agent prior to concreting which applied with a very light film. 2 . This failure can cause a dangerous collapse and gives serious impact on the appearance of the structural such as honeycomb. For example. formwork must set to line and level within the specified tolerance and include any camber or bend which may be required.1. The size and design of the panel should permit easy handling and simple method of erection and striking to reduce the incidence of blowholes. It also must have adequate strength to carry the working load and the weight or pressure of the wet concrete and to withstand incidental loading and vibration of the concrete.2 GENERAL DESIGN OF FORMWORK The formwork design must be sufficiently rigid to prevent undue deflection during the placing of the concrete. If the formwork is not rigid then the shape of concrete form when it is harden are not as original design. Furthermore. The joints between the formwork panels should be sufficiently tight to prevent loss of mortar from concrete. This will reduce its strength and the structure prone to collapse. these may lead to large deflections or leakage of mortar. When there is mistake in formwork design. Particular care is needed to provide sufficient number of form ties used to link together the opposite panel of a wall form. when using plywood as a formwork it is important to recognize that stiffness parallel to the face grain is less than the stiffness at right-angle to it. Arrangement of panels also should be such that they are not trapped during striking and it should be possible to strike side from beams without disturbing the soffit formwork. 3 . Thus. Furthermore. the formwork must have grout-tight joint. So that there is no honeycomb or fin produced. the time of striking should be related to the strength of the concrete and soffit forms to beams and slabs must be left in place longer than is necessary for the side forms. Concrete being a fluid when placed. 4 . it will take up the shape of the formwork which it must be the correct shape. self weight and any superimposed loads such as operatives and barrow runs over the formwork. This can be prevented by using sheet material or special self adhesive tape.1. The formwork must be accurately set out before the process of removing the formwork. size and in the right position.3 GENERAL REQUIREMENT OF FORMWORK Each formwork design should be strong enough to support the load of wet concrete which is generally considered to be approximately 2400 kg/m3. to prevent grout leakage. It must not be able to deflect under load which would include the loading of wet concrete. the requirement that need to be considered is hardness. moulded PVC and glass fibre reinforced polyester.2 Formwork Linings Formwork lining is functioning to give the smooth pattern or texture for the surfaces. The hardness of the formwork is significant to ensure that the formwork is strong enough to cater the concrete that is going to be place into it.1 Main Requirements In choosing the material for formwork.4 MATERIAL FOR FORMWORK 1.1. 1. 5 . This process will be done by lining the inside art of the formwork with various materials such as oil-tempered hardboard.4. moulded rubber. permeability and surface texture. Hardness is defined as the high resistance to various kinds of shape change when force is applied. Permeability on the other hand is the property where the material allows water to pass through its pores. Having good surface texture of formwork is the in order to get the best look of concrete once the formwork is removed.4. Surface texture is the physical condition of the formwork surface which is going result the appearance of the concrete. This requirement need to be considered to ensure that the formwork do not absorb too much of the concrete moisture. 2 shows the column stump formwork made up of timber.1 Figure 1. In order to use timber as formwork.1. the timber must ensure to have smooth and even surface. Figure 1. Figure 1.3 Timber Formwork Timber formwork is made up of timber.2 Plywood forms (in combination with timber) Plywood is an artificially manufactured wooden material available in different thickness and size used in formwork for concrete member. It is strong enough. decking and form linings in shuttering. It is also should be well-seasoned which is stable enough when it is exposed to the sun and rain. Comparing with other type of formwork. This kind of formwork can be easily produced manually with the desired shapes and sizes hence it is easily workable by hand or machine and can be nailed easily. 6 .4. Plywood is one of the mostly used materials for sheathing.1 shows the traditional timber formwork and Figure 1. durable and light weight. timber formwork has the most reasonable price. Advantages of Timber Formwork The main reason for the timber formwork widely used in construction is because it is economical for small projects as the price for timber is much cheaper as compared to other type of formwork material. This kind of formwork can be constructed by using the locally available timber which means the cost of production is very low. Timber formwork has the disadvantage of easily damage during fixing and dismantling of formwork. and bad flaws will leave imprint to the face of concrete. 7 . It could not be able to cater too much of loadings. Timber formwork also is easy to be constructed for any shape. size and height. The leakage through joints of timber will affect the efficiency of the formwork itself. Disadvantages of Timber Formwork However. timber formwork can be handled easily. It can break easily with improper handling. Therefore. Timber also has the excessive shrinkage due to the temperature changes which is going to affect the size of the formwork and result to poor shape of the concrete. Timber formwork can only be used up to 3 times in maximum which is not economical for the large construction where the formwork is required to be used many times. The pattern of grain. The weight of timber formwork is lighter as compared to steel or aluminium. with the light weight. knots. timber formwork is not really suitable for the large construction as the strength is not enough as compared to the metal formwork. The construction of formwork can be done even by unskilled labours with the proper apparatus and materials. 3 8 Figure 1.4 Metal Formwork (Steel) Steel formwork is made up of steel and has long life time and can be used multiple times as compared to the timber. The panels can be fabricated in large number in any desired modular shape or size.4. This type of shuttering is considered most suitable for circular or curved structures.4 shows how the steel formwork looks like. It is manufactured in the desired shapes and size and cannot be altered. Figure 1. This consists of panels fabricated out of thin steel plates stiffened along the edges by small steel angles.3 and 1.1. The panel units can be held together through the use of suitable clamps or bolts and nuts. Steel forms are largely used in large projects or in situation where large number reuses of the shuttering is possible. It also produce smooth finishes to the concrete surface as the formwork provide the smooth surface for the concrete. Figure 1.4 . Steel formwork is too heavy and make the handling process is difficult. Disadvantages of Steel Formwork’ Basically. 9 . Steel formwork not only gives very smooth finish to surface of member. steel formwork is higher in cost as compared to the timber. It has longer life as it can be used up to more than 100 times. hence it is economic for the big construction that requires multiple of formwork re-uses.Advantages of Steel Formwork As we know that steel has high strength and also durable. The fixing of steel formwork also can be easily done with the bolts and nuts. There will be no shrinkage in steel formwork due to the temperature changes as it will maintain its shape and size. it is also can be installed and dismantled easily. The production of steel formwork is done in manufacture industry and it is limited to the shape and structure which cannot be adjusted once it reaches the construction site. steel formwork is stronger to cater high load of the concrete. Therefore. Generally.6 10 . It has long life time and can be used multiple times as compared to the timber. Figure 1.5 Metal Formwork (Aluminium) Aluminium formwork is made up of aluminium.4.5 and 1.1. Figure 1. It also produce smooth finishes to the concrete surface as the formwork provide the smooth surface for the concrete.5 Figure 1.6 shows how the steel formwork looks like. However. aluminium formwork has not much different in term of characteristic with the steel formwork. it is lighter than steel due to the lower density. aluminium formwork has high strength and also durable. It has longer life as it can be used up to more than 100 times with the proper maintenance and refurbishment. Therefore. there will be no alteration is possible once the formwork is constructed.Advantages Similar with steel formwork. It is compatible only for residential apartments with repetitive layouts and restricted loads. Aluminum formworks become not cost effective if numbers of repetitions are less. Disadvantages Due to the fix shape manufactured. steel formwork is stronger to cater high load of the concrete. 11 . Aluminium formwork has high labour productivity as it is very light weight which makes it easy for manual handling. hence it is economic for the big construction that requires multiple of formwork re-uses. Disadvantages Due to the low load carrying capacity of plastic.4. If the formwork is carefully transported and used. 12 . Sculpture profile and repetition). It can be used for large section. interlocking system and can be used more than 100 times.4. Hence. It is use to produce a high quality surface finish (eg. the formwork can only cater for low loading of concrete. The disadvantages of glass fibre reinforce plastic is similar with plastic formwork. It can be used for simple concrete structures.7 Glass Fibre Reinforce Plastic This type of formwork is strong and light in weight.6 Plastic Formwork Plastic form work is a lightweight modular.1. it is not suitable for high construction. Furthermore. Advantages Plastic formwork is light weight shuttering hence requires less handling cost. Glass fibre reinforce plastic comprises of polyester resin reinforced with glass fibre. plastic formwork can be easily damage by heat. This type of shuttering is becoming popular for similar shape and large housing scheme. 1. The thickness of the formwork varies from 5 to 16 mm and can be used more than 100 times if handle with care. multiple reuses are possible making it highly economical. from applied coatings to form liner systems. Furthermore. It is the process that involves releasing agent that is coated on the formwork space prior concreting to facilitate easy removal of formwork.5. They are used in the storage of formwork and for concrete which will be hidden below ground.1 Neat oil with or without surfactant Neat oils are usually mineral oils and are suitable for all types of shuttering including steel formworks. Surface treatment is important for long life span of formwork. it can cause staining of concrete as it is not water resistant. They tend to produce blowholes and are not recommended for use for the production of high quality concrete surfaces. 1. neat oils with the addition of a small amount of surface activating or wetting agent minimize blowholes and have good form penetration and resistance to climatic conditions. it will produce an oily film on the surface that seem blemish. repeated or progressive use this neat oil will reduces the finish and leaves colour changes on finished surface 13 .1. The face contact materials each have individual texture and absorbency characteristics which require differing treatments to ensure the best possible results. Surface damage.5. poor / inconsistent surface finish and shorter life expectancy of the face contact material are all more likely upon omission of this vital area. While. Thus after application of this agent. If over application of this releasing agent. SURFACE TREATMENT Formwork surface treatments are now many and varied. Its appearance is not significance as we only applied for thin layer only. It is recommended for absorbent surfaces such as timber form not very suitable on steel formwork.2 Mould cream emulsion Emulsions of water in oil tend to be removed by rain. giving a safer surface to walk on unlike an oily film. Unlike chemical releasing agents. on soffit formwork. It doesn’t leave any oily film after it is dry. Chemical release agent more rate of coverage than conventional oils that can give a good quality finish surface. this agent cannot be used for concreting under freezing so it cannot be used in the countries that have four season climate. It provides high quality finishes and facilitates the work as it can be applied by spray only. Increased cost is compensated for by better coverage compared with the oil-based materials. it is expensive for a given volume but can be economical based on the application method as we only apply it for a thin layer. It is also not water resistant that tends to be removed by rain if it is constructed under exposed area. but minimize blowholes and are good general purpose release agents. They generally have good weathering resistance and water resistant that can maintain the coating under possible rainy area. For all high quality work. they are particularly suited to use in dusty. dry climates. they should be applied lightly by spray to avoid retardation. and in pre-stressed concrete applications. Even though. 1. 1. Thus.3 Chemical release agent It can be used for all types of formwork which are steel and timber formwork. 14 .5.5. 5. Wax treatments also come into this category.5.4 Paints and waxes These are not strictly release agents but are sealers which prevent release agents being absorbed into the form face. Presence of water on formwork’s surface can cause uneven finish as the water can seep through the formwork’s materials during hydration process of concrete occur. 15 . 1.1. They are not recommended for good class work and are seldom used.5 Water phased emulsion Emulsions of oil in water produce a dark porous skin on the concrete which is not durable. They are all particularly useful where it is necessary to avoid uneven porosity with consequent colour variations in the concrete surface and to give increased usage of the formwork. to have a better workability concerning the finishing operation.6. Blow holes are a cosmetic problem only and will not affect the long-term performance of the concrete structure. DEFECT 1. They are caused by air in the concrete being trapped against the form face.2.6. adjust batches on the jobsite by adding water.6. cavities on vertical surfaces of concrete. Usually small variation of moisture in concrete is acceptable but a different coloration can be easily perceptible when you compare the edge of two different concrete placements.1. the addition of calcium chloride to accelerate the setting time of concrete or the coexistence of poor mixing makes the concrete colour blotchy. Also. generally rounded. generally less than 15 mm across. 1. Some blow holes are almost inevitable unless a permeable formwork material is used. Uneven surface colour Discoloration problems may be caused by inconsistency in the mix design or by the quality of the aggregates (porous aggregate emerging the surface can absorb moisture and so the surrounding paste could be darker). 16 . Sometimes contractors. sometimes due to insufficient vibration. Blow holes Blow holes are individual.1. In addition the concrete should have adequate workability. The occurrence of blow holes can be minimised by the use of a suitable release agent on the surface of the formwork and the use of adequate vibration. 2 Inadequate of props Insufficient ties and props due to dirty forms with concrete from previous pour left on (ill-fitting joint). incorrect mixing of release agent. 17 .7. 1.4 Surface blemishes It can cause: Scabbing due to incorrect release agent – dirty forms. 1.7.7. props or wedges not tight enough. 1.7. Forms filled too rapidly. Metal locking devices not right enough in column or beam clamps. no enough to existing concrete that can cause pies. COMMON FAILURES OF FORMWORK 1.1 Dimensional inaccuracy Possible design deficiency is excessive deflection.7. lack of release agent Staining due to incorrect release agent – incorrect release agent.1. over or under application.3 Loss of material –ties or props incorrectly spaced Ties or props incorrectly spaced. 8. 18 . the concrete affected may be over stresses and cracked.3 No preconstruction plans of concrete casting. 1. Plus. This is because we have standard that must be follow for concrete casting and formwork removal then we know when the concrete are strong enough to cater the imposed loads. 1. the collapse of a floor resulted to the impact loading of the floor directly below it which also failed and collapsed to the lower floor.8CAUSES OF FAILURE 1. they can contribute to the failure of the structure. different types of formworks have different estimated time for formwork removal or reshoring process.1. or reshoring program When every stage do not have proper schedule.1 Premature removal of shores and reshores Movement of shores or reshores re removed too soon. For example. In extreme case there may be major failure to the building.8. This is also due to the structure cannot sustain its own self weight and deflection. formwork plans. removal of formwork schedules.8.2 Insufficient concrete strength Formwork failures results from insufficient concrete strength to sustain applied load after construction. and formwork for strip foundations. Foundation ii. Wall Foundation formwork Foundation formworks can be designed in various ways. Foundation formwork 19 . Basically there is a difference between formwork for individual foundations. The type of design is dictated by the size. normally designed as socket foundations. Slab v. Column iii. Beam iv. mainly by the height of the foundation formwork. The formwork for individual foundations is similar to column formwork and the formwork for strip foundations is similar to the formwork. Among them are: i.9 TYPES OF FORMWORK Formworks that have been used in construction sites came in several types.1. As the sizes of concrete column increases. Column formwork 20 . large heights and relatively high rates of concrete placement.Column formwork Reinforced concrete column forms are subjected to lateral pressure because of their small cross section. the stiffness of the formwork must be increased by either increasing thickness of sheathing or vertical stiffeners must be added to prevent sheathing deflection. Thus It is necessary to provide tight joints and strong tie support to the formwork. the thickness of the sheeting and cover straps and the width of a thrust-board. the width of the sheeting bottom is dimensioned so as to accept. Depending on the size of the beam. a special preparation table must be manufactured on site. Such individual parts are manufactured based on the beam dimensions specified in the project. For prefabrication of the formwork sheeting parts. Beam formwork 21 . at both sides of the width of the reinforced concrete column.Beam formwork Beam formwork has prefabricated formwork sheeting parts (sheeting bottom and side sheeting panels). The sheeting bottom and the side panels consists of sheeting boards nailed together by means of cover straps. The floor slabs can be structural slabs supported on a steel or concrete structural frame. or slab-on-grade. Structural slab formwork Slab-on-Grade formwork Slab-on-Grade Forms are forms for concrete slabs placed on grade. Slab-on-grade formwork 22 .Slab formwork Formwork for reinforced concrete slabs depends on the type of slabs to be constructed. These slab formworks are usually quite simple as concrete is placed on compacted earth or gravel levelled base. Thus no support is required for concrete at the bottom. Components of a wall formwork 23 . Ties and spreaders – These are used to hold the sides of the forms at the correct spacing.Wall formwork Formworks for wall construction are subjected to relatively lower lateral pressure than column forms due to their large cross-sectional area. Studs – to support the sheathing or Wales by forming a framework to keep the forms aligned and support the studs. The components of wall forms are: Panel sheathing – It is used to shape the wall and retain the concrete until it sets. Braces – It is used to prevent deflection of forms under lateral pressure and keep the formwork erect. 1 STRIKING OF FORMWORK Striking is the process of formwork removal in the process of casting concrete. Exposure conditions of the site As the mean temperature increases. thus increasing the striking time. Factors Affecting Period of Striking i. concrete containing blast furnace slag (GGBS) or pulverized ash requires longer striking period than normal Portland cement concrete. ii. to support the self-weight and any imposed loads.9. Weather of casting concrete The surrounding weather of the site also influence the striking time. the formwork is removed for further curing. Types of concrete used Different type of concrete needs different period of time to harden. This is because the concrete attain strength at an increased rate.1. iii. Soffit forms are usually left in place for longer periods and removed last in case of slab and beams. Once the concrete has achieved the initial recommended strength. For example. 24 . Cold weather retards the rate of setting and stiffness. the time required for removal of formwork reduces. Common examples for these admixtures are accelerators which reduce the setting time of concrete. v. 25 . Type and dimensions of structure Structural members like beams require more time before striking due to relatively bigger cross sections and being more critical element. as in walls and column sides.iv. Side forms are removed much sooner for curing. Admixtures or treatment to concrete The striking time can be brought down to the required value by adding admixtures to the concrete. The first one is timer formwork which is used for the 7 first floors. In the construction site. they use timber formwork from ground floor to 8 floors which take 3 weeks for concrete to harden whereas the use aluminium formwork from 8 floors to the top floor and the concrete only take 6 days to harden. 26 .10 CASE STUDY We have done site visit at Wangsa Maju for construction of high end apartment. This apartment more to reinforce concrete structure and do not use any steel structure. Figure shows the construction of timber formwork by the labours and the installation of the formworks on the surface of the building. Timber formwork used for those floors because of the uncertainty of the design of each floor as they consist of different facilities. there are two types of formwork used. For formwork. They provide for facilities from ground floor to 7th floor which include gym. shop lots and parking lots. swimming pool.1. This high end building consists of two blocks. one of the blocks has 21 floors and the other block have 23 floors. This apartment begins to construct at end of November 2016 and assumed to be completed one and half year from now which means 40% of the apartment have been constructed. Another type of formwork used in this construction site is aluminium formwork. 27 . This kind of formwork is used for the floor 8 and above because those floors consist of the same design of apartment houses in each floor. Since the floors are repetitive. aluminium formwork is sufficient and economical to be used since it can be used multiple times with the proper care and handling. Figure below shows the picture of aluminium formwork taken on the construction site. At the site. If it is not vibrated properly it may leave voids called “honeycombing.” The exposed aggregate leaves a honeycomb look and hence the name. Uneven colour surface is occurred due to the use of timber formwork. it tends to absorb the water in the concrete mix that later on will cause the hardened concrete looks dry. We know that timber formwork comes in various grains and surface. 28 . When concrete is poured into the foundation forms it does not just flow in like water and fill up the forms to the top. there are several defects that we can observe for example uneven surface colour and honey comb defect. One of the properties of timber formwork is absorbent. This first picture is of honeycombing in a footing. When concrete is poured in the formwork.