FORMWORK CPCCCA3019A Erect & Dismantle formwork for suspended slabs, columns, beams and walls

Learning Outcomes At the end of this session learners will be able to: erect and dismantle formwork to suspended slabs, columns, beams and walls to contain concrete in above ground construction including the use of timber, metal or prefabricated formwork of modular or in situ design.

Legislation & Information Applicable to FORMWORK Workplace, Health & Safety Regulation, 2011 Australian Standard for Formwork AS3610.1

FORMWORK INTRODUCTION This unit refers to the basic work practice of selecting, erecting and dismantling formwork. Erection, dismantling and maintenance refers to the putting together (assembly), taking down and taking care of the formwork used on a construction site, which is used to form a mould for the concrete to be placed into. Assessment of this unit is carried out in practical tasks involving the erection of formwork for suspended slabs, columns, beams and walls. These tasks must involve a demonstration of the skills required to assist in stripping, cleaning and storage of formwork. Formwork can best be described as a mould that shapes concrete, and is used extensively in the building industry. Some typical applications of formwork are: Footings Columns Slab-on-Ground Suspended Slabs Suspended Beams Walls

FORMWORK Suspended Slabs Formwork for suspended slab construction usually consists of one of the following: Timber/Formply Metal forms Modular Systems   Formwork Requirements Formwork is the temporary construction that gives form to and supports the freshly placed concrete. The loads carried by the formwork are considerable and it must be strong enough to support workers, materials and equipment as well as the concrete without movement or fear of collapse. It is often specially designed and supervised by an engineer. There are three main principles that must be observed in the design and construction of formwork. They are: Quality Safety Economy

FORMWORK Quality The forms, which shape the freshly placed concrete, will imprint in the surface of the concrete any defect present on the face of the form. Forms must be true to size, plumb, and square and correctly aligned in accordance with acceptable tolerances laid down in the specification. Four factors are important to good craftsmanship: Accuracy Rigidity Tightness of joints Finish

FORMWORK Accuracy The plasticity of fresh concrete allows it to be moulded into any desired structural or architectural shape. The moulds or forms are equivalent to a photographic negative of the concrete construction, any inaccuracy or blemish in the formwork being reproduced identically in the structure. It is therefore essential that forms be designed and constructed accurately, so that the desired size, shape, position and finish of the cast concrete structure are obtained. Wherever possible, forms should be set level with the finished top of the proposed concrete so that they can be used as a screed.

FORMWORK Rigidity Formwork should be of substantial construction to prevent distortion when supporting wet concrete. It should be sufficiently rigid to prevent: Bulging Sagging Movement

FORMWORK Bulging Bulging can be prevented by ensuring that the supporting members are strong enough to support all of the loads and are spaced in accordance with the specified centre-to-centre dimension.

FORMWORK Formwork must be braced to prevent movement in any direction. Its function and purpose is to maintain rigidity and stability. For suspended beams and slabs, lateral ties prevent the vertical supports from being displaced by knocking or from bending while under load.

FORMWORK Tightness of Joints Joints between intersecting members in direct contact with the concrete during placement, must be tight enough to prevent leakage of the cement paste. Leakage of cement paste will form unsightly fins and result in a honeycomb surface to the concrete. Any flaws in the concrete will require a considerable amount of work to restore the surface finish. Planed timber or form ply will provide a neater finish and is much easier to clean for re-use than sawn timber.

FORMWORK Finish There are several surface finishes, which can be obtained by treating the surface of the form. Industrial buildings generally require a smooth finish; however, simulated wood grain finishes can be produced by exposing the grain of timber forms by sand blasting. Special plywood sheets can also be made for this purpose. Joints, nails, screws, and tie wire leave unsightly imprints on the concrete surface. Always ensure that you provide a clear and even surface to the face of the forms.

FORMWORK Stripping When formwork is stripped, ensure that safe and damage limiting procedures are used, for example, supporting components during the process. Safety There are two aspects of safety, which must be observed: Strength, design and construction of formwork and supporting components Work procedures

FORMWORK Strength, Design & Construction The dead load of the fresh concrete and reinforcing steel is approximately 2500kg (per cubic metre). It is essential that the formwork and formwork components are strong enough to support the concrete and all other imposed loads. While the design and the supervision is the work of a specialist (Engineer), you can contribute to the safety of the job by ensuring that directions and specifications are strictly observed.

FORMWORK Work Procedures The safety of yourself and other workers on-the-job can be ensured if safe working procedures are practiced at all times. The following safety factors must be observed: Keep the work area clear of off-cuts and loose materials. Make sure that all structural components are firmly fixed before leaving the job; even for a few minutes. When you have finished using a particular tool, put it in your toolbox. This practice will prevent it from being lost or from falling on a work mate. Ensure electric leads and air hoses do not create tripping hazards. Immediately report unsafe equipment or structural components when they are noticed to your supervisor, and always warn your fellow workers. Ensure that handrails and kickboards are in place and securely fixed. Observe safety signs and wear your safety clothing and equipment at all times while on the job.

FORMWORK

FORMWORK OBSERVE SAFETY SIGNS and BARRICADES Formwork can collapse as a result of faulty design or careless workmanship. A collapse may result in costly structural damage or, more seriously, injury or even loss of life. Safety is of particular importance to workers involved in the construction and removal of formwork. Always ensure that you pay attention to constructional details and observe correct working practices.

FORMWORK PREPARATION OF FORMS FOR CONCRETING Cleaning All dirt, mortar, wood chips, sawdust, etc. must be removed from inside the forms before concreting can commence. If the bottom of the form cannot be reached, then clean out holes should be provided at suitable points to permit the removal of foreign matter. A jet of air or water can often be used effectively to remove debris. All clean out holes must be carefully closed after cleaning out the forms. It is important to clean out this debris as it may be seen in finished concrete, cause air bubbles and imperfections, compromise strength and expose reinforcement.

FORMWORK Release Agents (Form Oils) Most form materials require the application of a release agent to the surfaces, which will make contact with concrete. The following are the requirements for release agents: Act as a parting compound to facilitate the easy release of forms without concrete sticking to their surfaces. Act as a sealer to prevent the forms absorbing water from the concrete. Not to stain or disfigure the concrete surface. Not to leave a surface deposit this will prevent adhesion of a subsequently applied render, paint or other material.

FORMWORK Types of Release Agents Release agents (also known as form oils) are generally one of six types: Neat oil Mould cream (water emulsified into oil vehicle) Water soluble emulsion (oil emulsified into water vehicle) Neat oil with additives (surfacing or wetting agents) Chemically reactive agents Barrier paints and coatings Application of Coatings Surface coating should be applied to smooth, clean surfaces by roller, brush, spray, wiping, etc, depending on the type of coating. Coverage must be complete and uniform for good stripping and appearance. There should be no excess coating to stain the concrete.

FORMWORK Cleaning of Formwork Any concrete adhering to the forms must be removed before re-use of the forms. The sooner it is removed the easier it will be and less sustained by the forms. Different means are used on the various materials: Steel Forms - metal scraper Plywood Forms - stiff brush Sawn Timber - metal scraper Glass Reinforced Plastic - brass brush   Install Blockouts When the formwork is in place but prior to the placement of the concrete all services to be built-in must be accurately placed according to the drawings and firmly fixed in position so as not to move during the concreting procedure. Blockouts or core holes for service penetrations or other structural elements must be accurately positioned and firmly fastened to the formwork or reinforcing steel, if applicable. Polystyrene foam, shaped to the required size and detail, is often used for small and sometimes large block outs. At other times, timber formwork, capable of being easily dismantled at removal, is fabricated and installed prior to the placement of the concrete.

FORMWORK 2. REMOVE AND RECLAIM FORMWORK Removal of formwork for suspended concrete slabs should not be undertaken by inexperienced persons. Removal of formwork before concrete has gained sufficient strength to support itself and the loads placed upon it will result in failure of the concrete. In many cases the engineer will require back propping for continued support after the formwork has been stripped. Ideally, formwork should be left in place as long as possible to provide protection for the corners of edges and to assist with curing. Stripping formwork requires considerable care on the part of workers to avoid damage to the green concrete. Concrete can easily be damaged by scratching and shipping, even though it may have developed sufficient strength to support itself. Care must be taken to protect the concrete and to extend the useful life of the forms by careful handling. Not only must the forms hold together, but they must remain dimensionally accurate and stay in good condition to make accurate alignment and clean joints possible. Form panels and column, wall and floor components should not be dropped. ALL NAILS SHOULD BE REMOVED FROM FORMWORK

FORMWORK 3. PREPARATION FOR STORAGE To prevent steel forms rusting during prolonged storage it is advisable to coat them with a thin film of oil, of a type that will not damage the concrete. If sump oil is used, it will need to be removed before the forms are re-used for columns, which are to be cement rendered. 4. STORAGE If the forms are to be re-used later, it is important that they are: Stacked to prevent distortion Stacked to prevent rising dampness Protected from heat/wind/rain and Protected from contact surfaces The above information dealing with the removal and reclaiming of formwork, preparation for storage and storage is general information for all participants.

FORMWORK 4. Studs and Wales  Studs and wales are used in wall formwork or edge beam construction. Studs are the vertical members and wale the horizontal.   5. Starter bars Starter bars are the reinforcement bars that are protruding out from previously poured concrete. They help to tie in between joins from column to slab or slab to column. 6. Braces/Props Braces and props are used to secure formwork columns and walls and to help straighten and align. They are needed to add to the strength and stiffness of the formwork during the pouring of the concrete.