INSTITUTO SUPERIOR TÉCNICO MESTRADO EM ARQUITETURA_2014/2015. Joana Alves Samúdio EXTENDED ABSTRACT

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1 INSTITUTO SUPERIOR TÉCNICO MESTRADO EM ARQUITETURA_2014/2015 Joana Alves Samúdio EXTENDED ABSTRACT FAÇADE COVERING WITH PANELS REINFORCED WITH GLASS FIBER (GRC) The use of GRC prefabricated systems and solutions is more and more frequent in the construction sector. This tendency has been stimulated by the many advantages this type of production brings to the sector, as for instance the quickness of work execution and the quality of the elements produced, as well as their versatility, being adaptable to different applications. The use of GRC panels is a relatively recent covering solution in Portugal, although quite common in countries such as the United States, Japan or Spain. However, at national level, the resort to this kind of solution is not yet frequent, mainly due to the high cost of such covering material and the lack of investment in the civil construction sector, in view of the current economic context. From the architectural perspective, GRC panels offer great versatility in the conception of façades. This versatility translates into the possibility to create panels of big dimension and complex geometry, as well as access to a wide variety of finishes. The present essay aimed the identification of the potentialities and knowledge on the application of prefabricated fibre glass reinforced concrete façade panels (GRC). The intention was to systematize the processes of production, conception and installation of GRC panels. This systematization was designed to establish the different factors to be considered in the construction of buildings that use this type of covering. More specifically, how the panels should be shaped, based on their fixing to the building s solid structure, on the fixing system and joint solution applied. Considering that the use of prefabricated elements is still a distrusted construction system, the purpose was also to demonstrate the advantages of this kind of solution, aiming a more systematic employ. 1

2 PREFABRICATION From the end of the 18th century on, with the Industrial Revolution, the mechanization of the productive process takes place, passing from the artisan shop to the factory (Fernandes, 2009). All through the 19th century, new materials are developed, such as cast iron and glass, and later, the industrial production of concrete and steel introduces the first prefabricated concrete products, which involved significant modifications in the construction sector. The term prefabrication refers to the practice of producing building components of standard dimension, industrially, in a place other than the worksite. Construction comprising prefabricated elements considers the normalization of such elements, rationalization of the application techniques and control and systematization of the manufacturing processes, presupposing the organization of production according to optimization criteria, including the processes of transport, installation and quality inspection and control. The post-war reconstruction processes were the main drivers of prefabricated construction, introducing a form of massive construction based in large units, often corresponding to type projects. However, these early experiences in the field of prefabrication had little repercussion, for lack of economic viability of the prefabrication processes used and for the difficulty in competing with traditional construction (Pinto, 2000). Therefore, until the early 70s, prefabricated construction was characterized by the use of large and weighty panels (Pinto, 2000), giving rise to urban environments of great homogeneity, quickly associated to poor quality construction (Sousa J., 2010). From middle 70s on, occurs a decline in heavy prefabrication in western countries. This was justified by the prefabricated market downfall, which encountered then great social rejection due to the monotonous and monolithic uniformity brought by the solutions offered (Santiago, 1999, p. 68), and by the occurrence of a few accidents in buildings constructed with big panels (Oliveira & Sabbatini, 2003). Furthermore, housing needs in the industrialized countries were met and heavy prefabrication processes implied major financial investments. The heavy prefabrication rejection was also associated to a greater attention given to construction quality, environmental comfort standards and component offer diversification. In the period between 1970 and 1985, the production of prefabricated elements evolves to open prefabrication systems, so as to give answer to the market s growing demand concerning flexibility and form variation. The innovations occurred in the 19th century last decades, mainly in the area of construction technology, created great impact and contributed significantly for a higher efficiency in production processes and final product quality. In the field of prefabrication, this translated into the production of new components façade elements, giving rise to lighter and more resistant pieces, often by incorporating other materials. 2

3 THE FAÇADE With the development of resistant structures, the façade gradually lost its structural function and began to be conceived autonomously, acting as skin to the building. When structure no longer conditioned the dimension, form or number of openings, it allowed the dematerialization of the surrounding elements. All of that increased the façades freedom of design and specialized its conception in the building s global project. A fundamental aspect in façade conception is the external covering selection. The external covering has direct influence on the conditions of salubrity and habitableness inside the building. It must protect the crude wall from the action of many aggressive agents, being resistant to those agents, must reinforce water tightness, offer flatness, verticality and superficial regularity features and, at the same time, produce the decorative effect intended (LNEC, 1995). The need to reduce the environmental impact of the construction sector and the energy consumption in buildings has led to an increased attention to coverings selection. The use of prefabricated components for façade covering is currently common practice in the civil construction area. These components attest the final quality of work, when high-quality materials and qualified workforce are involved, as well as high-level control in production and installation on site. The new covering materials offer great advantages, mainly better resistance and subsequent reduction of components volume and weight, ease of installation and durability (Mateus, 2004). This fact introduces flexibility in architectural conception, ease and quickness of installation on site, reduction of conclusion dates and subsequent reduction of costs. GRC FAÇADE PANELS The development of construction technologies has allowed altering and exploiting construction aesthetics through the introduction of new composite materials and components, and structural solutions. There are many diverse materials available in the market to create façade covering panels. To create lighter panels, there are, in the class of cementitious materials: light aggregate concrete, autoclaved concrete, polymer concrete or glass fibre reinforced concrete (GRC). It was in the context of evolution of materials engineering that were explored the first applications of glass fibre to reinforce concrete and that were developed GRC façades. The first uses of fibre as reinforcing material happened in the 30s in the USA, in the context of the polymer industry. In the 50s, the first experiences in the use of fibre to reinforce concrete took place, but it was in the 60s that significant advances occurred in the field of this material, as a result of the first studies carried out on the composite. In the early 70s, the Pilkington Brothers company obtains a patent on glass fibre, that is initially commercialized under the denomination of Cem-FIL AR. 3

4 Glass fibre reinforced concrete, or GRC, is a composite material formed of a concrete matrix, sand, water and additives, where glass fibres of short length, usually 1-5 cm, are disseminated (Ferreira, 2001, p. 1). The presence of fibres offers great deformation absorption ability and considerable resistance to efforts of traction, flexion and impact (Sousa F.M., 2010). Therefore, when the panel is subject to efforts of traction, the fibres will delay the occurrence of fissures, by amplifying the matrix resistance to fissure. GRC panels can attain high resistance, in conformity with their weight which is quite reduced. This reflects in the reduction of the panel weight, which can be 1/6 of the weight of an equivalent element in reinforced concrete (Fernandes J.L., 2008). These panels can be characterized according to three types: 1) shell; 2) stud frame and 3) sandwich, besides simples panels, generally used to create smaller pieces. The panel production method is selected in accordance with geometry and kind of solicitations the panels will have to endure throughout their lifetime. The process of production must allow the incorporation of sufficient fibres, so as to attain the intended reinforcement of each specific work. There are several methods of production of GRC panels, the two main being the direct projection or spray-up method and the premix method. The spray-up method is the most commonly used in the production of panels, due to its efficacy and easiness of execution. In this process, there is a simultaneous projection of concrete mortar and glass fibres, by means of a projection gun. GRC panels may receive different techniques of finishing, for aesthetic purposes or to reproduce other materials. Finishing may be applied in the production phase or after panel demoulding. GRC panels enable architectural versatility, as they offer a wide variety in terms of geometry, dimensions, colour and texture. This versatility is possible, because these panels are uniformly reinforced, overcoming the limitations imposed by reinforcement difficulties. The moulding determines the panels dimension and mass, and is directly related to deformities induced by temperature and humidity variations. The panel must be dimensioned so as to be resistant to forces and charges transfer, it may be subject to during its useful lifetime. The panels design must consider the effect of its own weight, the action of wind and temperature and humidity variations, so that cyclic movement occurs freely not creating tension beyond panel or fixing resistance. In generic terms, the design of a panel comprises the following stages: definition of panel geometry and dimension, considering the limitations of transport; definition of agents the panel will be subject to (own weight, wind, temperature variations, etc.); determination of panel thickness; confirmation of previous values, considering resistance to flexion; identification of fixing systems and respective application points. The dimensioning of joints between panels is also an important stage in the façade project, as it is their function to accommodate production tolerances and cyclic movements of expansion and retraction the panels are subject to. The joint areas are generally critical points in the façade performance, being exposed to inclement 4

5 weather and subject to different solicitations. The dimensioning and choice of material should consider the level of façade performance expected, the building s function, the façade orientation and economical aspects. CASE STUDIES An analysis was made of the solutions used in six buildings established as case studies, namely: Secondary School Rainha Dona Amélia in Lisbon; Secondary School of Pombal; Secondary School Jorge Peixinho in Montijo; Vodafone Headquarters Building in Lisbon; Almada s Preventive Cardiology Institute in Monte da Caparica; and Psychiatry and Mental Health Department in Beja. This analysis intended to: 1) identify the covering area where GRC panels were applied; 2) determine the fixing system used and how it was connected to the solid structure; and 3) determine the type of joint used. The selection of these case studies was based on works with panels produced by the company Prégaia. This choice was justified for being the leading company at national level in the production of façade panels. It was established that GRC is a material of attractive characteristics enabling multiple applications. CONCLUSIONS One of the great advantages, at architectural level, was proven to be the possibility to combine different panel typologies stud-frame, sandwich or nervured in the same building. This gives homogeneity to the façade in terms of material, although different application solutions may be at use. Another advantage is the possibility to offer a wide variety of finishes for the panel: polished, textured, pigmented or engraved. The absence of steel reinforcement increases these panels resistance to corrosion, becoming a solution adequate to maritime environments. This fact reflects on the covering higher durability, maintaining its mechanical and aesthetic features for longer. Based on a relation of cost-benefit, the stud-frame typology proves to be more expensive, as it does not serve directly a function in terms of the façade thermal performance. The choice of the stud-frame panel typology is solely motivated by architectural reasons, serving a mainly aesthetical function, unlike the sandwich typology, which comprises thermal insulation and contributes for the building s performance. This system may even replace the insulation system, in case of adoption of a sealed joint system. The use of GRC panels in the covering of façades is a solution still concentrated in some countries, such as Spain, United Kingdom, United States, Canada and Japan. The introduction of this system in the Portuguese market represents the possibility of an efficient technology of façade covering and the establishment of new fields of action for the manufacturers of prefabricated elements, with a real advantage for architects and work providers. 5

6 REFERENCES Fernandes, A. (2009). Habitação (colectiva) Modular Pré-fabricada: Considerações, origens e desenvolvimento. (Tese de Mestrado em Arquitetura). Faculdade de Ciências e Tecnologias da Universidade de Coimbra, Coimbra. Fernandes, J. L. (2008). Tratamento de Juntas em Painéis de GRC. (Tese de Mestrado em Engenharia Civil). Faculdade de Engenharia Universidade do Porto, Porto. Ferreira, J. P. (2001). Caracterização Estrutural do Betão Reforçado com Fibra de Vidro (GRC). Aplicação a Torres de Telecomunicações. (Tese de Doutoramento em Engenharia Civil). Instituto Superior Técnico, Lisboa. LNEC. (1995). Curso de Especialização Sobre Revestimentos de Paredes. (2º ed.). Lisboa: LNEC. Mateus, R. (2004). Novas tecnologias construtivas com vista à sustentabilidade da construção. (Tese de Mestrado em Engenharia Civil). Universidade do Minho, Guimarães. Oliveira, L. A. (2002). Tecnologia de Painéis Pré- Fabricados Arquitectônicos de Concreto para Emprego em Fachadas de Edifícios. (Tese de Mestrado em Engenharia Civil). Escola Politécnica da USP, São Paulo. Patinha, S. (2011). Construção Modular - Desenvolvimento da ideia: Casa numa Caixa. (Tese de Mestrado em Engenharia Civil). Universidade de Aveiro, Aveiro. Pinto, A. (2000). A Pré-fabricação na Indústria da Construção. 1º Congresso Nacional da Indústria de Pré- Fabricação em Betão. (pp ). Porto: ANIPC. Santiago, A. (1999). Pré-fabricação aberta e pré-fabricação fechada. 3º Jornadas de Estruturas de Betão. (pp ). Porto: Faculdade de Engenharia da U. P. Sarabanda, C. (2013). Habitação Modular Evolutiva. (Tese de Mestrado em Engenharia Civil.) Instituto Superior de Engenharia do Porto, Porto. Sousa, F. M. (2010). Fachadas Ventiladas em Edifícios. Tipificação de soluções e interpretação do funcionamento conjunto suporte/acabamento. (Tese de Mestrado em Engenharia Civil). Faculdade de Engenharia Universidade do Porto, Porto. Sousa, J. (2010). Potencial de Aplicação de Sistemas Pré- Fabricados na Reabilitação Térmica de Fachadas.(Tese de Mestrado em Engenharia Civil). Universidade do Porto, Porto. 6