See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/318373680 FORMWORK FOR MODERN AND VISUAL CONCRETE CONSTRUCTIONS Conference Paper · May 2017 CITATIONS READS 0 5,457 3 authors: Naser Kabashi Cene Krasniqi faculty of civil engineering and architecture,Kosovo University of Prishtina 71 PUBLICATIONS 54 CITATIONS 29 PUBLICATIONS 21 CITATIONS SEE PROFILE SEE PROFILE Qani Kadiri University of Prishtina 5 PUBLICATIONS 19 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: COMPARISON THE BEHAVIOUR OF RC BEAMS WITH GFRP, CFRP AND STEEL REINFORCED BARS View project Behaviour the Rigid pavements structures reinforced with fibres View project All content following this page was uploaded by Naser Kabashi on 12 July 2017. The user has requested enhancement of the downloaded file. FORMWORK FOR MODERN AND VISUAL CONCRETE CONSTRUCTIONS 1Kabashi,N., 1Krasniqi,C.,1Kadiri,Q.,1Sadikaj.A.,2Morina.H. 1 Department of Civil Engineering, University of Prishtina, str. Bregu I Diellit nn.10000 Prishtine, Kosova 2 Institute of Building Materials and Structures “IBMS” Prishtina, str A.Ramadani 74/2, 10000 Prishtine, Kosova ABSTRACT Concrete as an architectural and structural material has passed many evaluations during the past decade, always in increasing interest from the architects and engineers to realize the attractive and durable design. The finishing surface of concrete, such one the requested parameter is on functions of many variables. The mix design, techniques of concrete compaction and caste in place, surface treatment, type of formworks, are some of factors which directly will indicate the durability quality and visual aspects of concrete in structures. In order to achieve a good release performance, easy application and cleaning of the formwork, without any defects, it is important to use the right release agent technology and formwork typ. Moreover the application of resource friendly technologies with a high degree of sustainability is becoming more and more important every year in modern and esthetic visually of concrete constructions. Keywords: Formwork; visual concrete, durability, quality, agents, ect 1. INTRODUCTION Concrete construction has gone through significant changes since the early 1990s and continues to develop. Innovations in formwork, concrete as a material, and reinforcement developments are just three of the contributors to what has become a significantly quicker, safer and less wasteful form of efficient construction. The concept of modern concrete incorporates main and secondary materials which are by-products from other industrial processes, such as fly ash, silica fume and ground granulated blast furnace slag (GGBS), which minimize the usage of Portland cement. This is a orientation of both economic and environmental parameters to involve in one. The final results of concrete constructions in actually design of modern concrete is in direct relations with formwork, including the types and benefits in different types of frameworks. The new formwork systems are reusable with little waste generated compared to traditional formwork. The assembled units are intended for use throughout the duration of a project without dismantling. Increased speed and time efficiency on-site. The repetitive nature of the work, combined with the engineered nature of the formwork, allows site teams to finely tune their operations, which in turn leads to minimal concrete wastage. 2. FORMWORK SYSTEMS The construction of formwork takes time and involves expenditure up to 20 to 25% of the cost of the structure or even more. Design of these temporary structures are made to economic expenditure. The operation of removing the formwork is known as stripping. Stripped formwork can be reused. Reusable forms are known as panel forms and non-usable are called stationary forms. Timber is the most common material used for formwork. The disadvantage with timber formwork is that it will warp, swell and shrink. Application of water impermeable cost to the surface of wood mitigates these defects. On the process of the development technology in civil engineering works are developed the different types of concrete formwork. In general the formworks systems based on the materials, presented in fig.1, are: Plywood Formwork Steel Formwork Aluminum Formwork Plastic Formwork Vacuumatics 3D formwork Fabric formwork a/Plastic formwork d/ aluminum formwork b/ plywood formwork c/ steel formwork e/ fabric formwork f/ vacuum 3D formwork fig.1. Types of formwork/a.b,c.d,e,f) Each of the system must to fulfill the requirements for formwork: Easy removal Economy Strength Rigidity Less leakage Smooth surface Light weight Quality Supports Two major categories of formwork are job built and prefabricated. Job-built forms are often designed, built, and used with the particular requirements of a single project in mind. They are most often constructed using plywood sheathing and lumber framing. They may also incorporate proprietary hardware in their assembly. Prefabricated or commercial forms are usually constructed with materials that can be reused many times. Their higher initial cost is offset by the potential for more reuse cycles than job-built forms of lumber and plywood or possible cost savings from increased productivity in erecting and stripping the forms. Commercial concrete forms may be of standard design or custom built for a particular application. Some types of commercial forms are designed to span relatively long distances without intermediate supports. Some girder forms of this type are constructed so that the sides of the forms behave like a plate girder to carry the dead and live loads. The main concrete elements for different positions and forms are constructed on the formwork system, which will be:[3],[4],[5]. Flat slabs Columns formwork Ribbed and waffle slabs Beams and slabs Post-tensioned slabs Tunnel form Table form Fig.2. Formworks for different types of concrete elements 3. HOW FORMWORK AFFECTS VISUAL AND MODERN CONCRETE QUALITY Architectural modern concrete compare with common structural concrete in focused of exposed surfaces or forms may be more important than the strength of the members. The properties of fresh concrete are such that it may be cast or molded to produce any shape that forms can be made. A variety of structure may also be obtained by adding a color or admixture to the concrete mix or by adding a surface coating on the formwork or after the concrete has hardened. The surfaces may be extremely smooth or they may be quite rough, depending on the desired effects. The appearances of large and possibly drab areas can be improved greatly by the use of recessed or raised panels, rustications, ornaments, and other designs. Metal molds can produce concrete having extremely smooth surfaces. A variety of surface patterns can be obtained using form liners that are placed on the inside of plywood sheathing. A large variety of shapes is available from companies that supply formwork accessories. Permits the forming of concrete with a great variety of intricate details, such are: Stained Concrete; Stamped Concrete; Form Liners; Smooth-Surfaced Concrete; etc. In this research works we are focused on the smooth surface of concrete, such a parameter for visual and modern concrete, and the formwork effect in concrete and concrete quality. The selection and construction of good quality formwork is fundamental to achieving a good finish. Impermeable linings such as steel, polypropylene, Glass reinforced plastic (GRP) and high density overlay (HDO) board produce a smooth, shiny surface whereas timber, unsealed plywood, paper faced or medium density overlay (MDO) boards give a matt finish.[7]. Fig 3. Formwork for architectural Modern Concrete The increasing idea for creative and organic shapes in modern architecture, although it is not always easy to realize the architect designs. Theoretically, concrete is the perfect material to make all kind of various shapes since, after all, fresh concrete can be poured into any formwork shape. Traditional formworks however are very stiff and straight-lined, rendering flat walls, and rectangular beams or columns. These panel formworks are often the limiting factor for more organic architecture. Flexible fabric formwork might create new possibilities for designers and contractors to realize these kind of organic shapes. Realizations of the requested idea is on the direct relations with type and characteristics of formwork. Formwork cannot avoid impacting the surface appearance of concrete. The impact can be controlled, however, by using formwork that has benign interactions with the concrete and has consistent contact surfaces. For satisfactory appearance, formwork has to be accurately placed, rigidly installed, and have tightly sealed joints. Forms should be clean, maintained, and used a consistent number of times. In some cases, forms may be limited to a single use if the conditions dictate. Forms should be sealed with non-vapor-transmitting coatings, and form release agents should be used to achieve consistent form removal. Consistent formwork in consistent conditions with benign interaction with the concrete is necessary for uniform-appearing architectural concrete. From practical point of view also the curing structural concrete apply to architectural concrete, must be in considerations for architectural concrete. A consistent curing process should begin as soon as possible and be consistently maintained among the different pours. Because it is easier to achieve consistent results with curing compounds, architectural concrete should not be wet-cured. But to make the curing more uniform, concrete should be consistently misted before applying curing compounds. Generally some unexpected event causes one member to fail, then others become overloaded or misaligned and the entire formwork structure collapses. The main causes of formwork failure are: improper stripping and shore removal inadequate bracing vibration unstable soil under mudsills inadequate control of concrete placement lack of attention to formwork details. 4. CASE STUDY – APPLY THE REALESE AGENT IN IMPROVEMENT THE CONTACT FORMWORK-CONCRETE Formwork needs to be treated with a release agent so that it can be removed easily after the concrete has set. Failure to use a release agent can result in the formwork sticking to the concrete, which may lead to damage of the concrete surface when it is prised off. A single application of release agent is all that is required when forms are then used. Care must be taken to cover all the surface that will come in contact with the surface of concrete. However, if there is an excess of release agent, it may cause staining or retardation of the concrete. There are different release agents depending on what material is used for the formwork. The three most common release agents for formwork are: 1. Neat oils with surfactants: used mainly on steel surfaces, but also suitable for timber and plywood. 2. Mould cream emulsions: good general purpose release agents for use on timber and plywood. 3. Chemical release agents: recommended for high quality work, applied by spray to all types of form face. Before the concrete is poured into the formwork, it must be checked by someone who has been trained to inspect formwork. Depending on how big or complicated the pour is, the inspection may just take few minutes or it could take hours. Only when the formwork has been approved, may the pour take place.[8]. In our case the type of release agent DMA 1000, MAPEI producer. The effect of the release agent it will be focused in the some lines in concrete. We used some of graphical forms just to check the visual in concrete with and without the release agent, presented in fig 4a , 4b & fig 5. Fig.4a. Visual surface of concrete with DMA 1000 Fig.4b. Visual surface of concrete without DMA 1000 Fig. 5. Visual surface of concrete with DMA 1000 The realization and using the DMA 1000 is done in positions: concrete wall, prepared and placed the concrete in properly way. Before placing the concrete are checked the some properties of fresh concrete, just to verify the workability and pump ability of concrete. The preparing activities are presented in following fig 6. Fig.6. Necessary activities before the placing the concrete in formwork 4.1.Concrete parameters for properly cast in place The properly cast in place of fresh concrete is directly in relations with main properties: - Workability Air entrainment Cohesively of the fresh concrete stability, mobility and compactability Using the chemical admixtures Concrete High placement Oriented parameter for our case study are presented in table 1. Table1- properties of fresh concrete Main Properties of fresh Concrete at the cast in place Workability/Consistency Air Entrainment Chemical Admixture High placement temperature Formwork s= 160 mm/ S4 Mapefluid AC2 Max 4 m Max 30 0C plywood 3.5 % Full filling the all requested properties concrete as just a plain surface with the commonly held characteristic appearance of ‘looking like concrete’ can be ‘improved’ by grit-blasting a ‘Picasso’ on the surface. The surface is still the same surface; however, the eye is now drawn to the interesting sketch almost as if it were a kind of graffiti. Decorative, by definition, means ‘adoring; suited to embellish’. I would suggest concrete can either be made decorative or is decorative without post-applied treatment. The appreciation is in the eye of the beholder. I would argue that it is the skill of the designer, user or applicator that makes concrete decorative.[ Graham F TrueDecorative &Innovative Concrete], presented in fig7. Fig. 7. Decorative concrete in buildings Another effect of visual modern concrete, especially in facades of building in Prishtina, was in progress in buildings built about 1970. Today the interest is on increasing process for details in facades in more important buildings. Some of building are presented in following fig 8 &fig 9. Fig.8 a. Building of Faulty of Civil Engineering Fig.8.b. A part of Prishtina –visual concrete in facades Fig.9. A part of Prishtina –visual concrete in facades 4. CONCLUSIONS In many cases, based on the architectural request for visual modern concrete, the effects in output results is multi functionality. The texture of cast in situ concrete is typically dictated by the formwork facing material providing an ‘as struck’ finish. The selection and construction of appropriate, good quality formwork is fundamental to achieving a good finish surfaces such nature concrete or surface and texture can be created by lining the formwork with a material to create the surface. Based on the experience and applications of different types of formwork we can conclude: Concrete contractor will determine the formwork required to meet the required finish or performance of specification. This specification puts the onus on the designer to ensure that this form finish will give them the appearance required. The formwork should be grout tight and all joints between panels sealed with an appropriate clear non-staining sealant to eliminate any grout loss. Release agents help prevent the concrete binding to the formwork. The release agent must be non-staining and not wash off during wet weather, nor break down over the concrete curing period. The release agents must be compatible with the admixtures in the concrete and the formwork used. The properties of fresh concrete will fulfilled the requested parameters to eliminate many additional nonliked effects , such are: segregation; bleeding; 5. REFERNCES [1] David Bennett; Architectural In situ Concrete; RIBA Publishing, 2007 [2] Graham True; Decorative and innovative use of Concrete; Whittles Publishing;2013 [3] Robert L.Peurifoy;Garold D.Oberlender: Formwork for Concrete Structures;McGrawHill,2011 [4] APA; Concrete Forming:Design/Construction Guide/; 2012 [5] David W.Johnston; Design and Construction of Concrete Forwork;Concrete Construction Engineering Handbook; [6] Aberdeen Group; Effects of formwork on concrete; PublicationsC370429, 1973 [7] John J Orr; Anthony P Derby; Tim J Ibell: Concrete structures using fabric formwork; Journal :Structures. [8] Mapei:Form Release Agent DMA 1000; Technical Specifications [9] John Gambatese, PhD, PE;Andre Barbosa, PhD;Amrutha Das : Use and Re-use of Formwork:Safety Risks and Reliability Assessment, September 2014 [10] Kamran M. Nemati; Temporary Structures Formwork for Concrete; TOKYO INSTITUTE OF TECHNOLOGY,2005 [11] N.Kabashi;Technology of Concrete; University of Prishtina, 2006 View publication stats
