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Abstract(s)
Em virtude das mudanças climáticas globais que se têm vindo a sentir nas últimas décadas, cada vez mais observam-se fortes precipitações no nosso país e em vários locais do mundo. A aplicação de misturas betuminosas drenantes nas camadas de desgaste em rodovias tem como objetivo controlar o escoamento superficial e, consequentemente, aumentar a sua segurança de circulação. Recentemente, a aplicação destas camadas tem aumentado verificando-se o seu uso principalmente na Europa e Estados Unidos da América.
As misturas betuminosas drenantes são aplicadas na camada de desgaste dos pavimentos rodoviários devido às muitas vantagens que apresentam, tais como, o aumento da segurança de circulação durante a precipitação e a redução do ruído. Graças à sua estrutura com elevada porosidade, as misturas betuminosas drenantes permitem que a água seja drenada e percolada no seu interior, sendo escoada para a berma ou para sistemas de drenagem apropriados adjacentes à camada, o que reduz os efeitos de pulverização, aumentando a visibilidade dos condutores durante os períodos de chuva. Contudo, e apesar das vantagens descritas anteriormente, a aplicação destas camadas possui algumas limitações. As grandes desvantagens das misturas betuminosas drenantes são a colmatação dos seus vazios e a sua durabilidade. Muitos dos efeitos funcionais negativos resultam do prejuízo que as águas superficiais provocam na segurança e nível de serviço de circulação. Para melhorar a qualidade das misturas betuminosas drenantes vários estudos e pesquisas têm sido realizados por todo o mundo.
A presente dissertação incide o seu estudo na avaliação da influência da ação da água nas misturas betuminosas drenantes e do efeito da adição de fibras celulósicas na sua composição, comparando o seu desempenho com as misturas drenantes sem esta adição. Inicialmente, realizou-se a sua formulação baseada na baridade, na porosidade e na perda de massa por desgaste, efetuada através do ensaio cântabro seco e imerso, obtendo-se o teor ótimo de ligante betuminoso. A avaliação destas misturas realizou-se através dos ensaios de determinação do módulo de rigidez por tração indireta, sensibilidade à água e permeabilidade. Através do trabalho laboratorial concluiu-se que as fibras celulósicas contribuem para a melhoria das propriedades de coesão e reforçam as misturas betuminosas drenantes, permitindo um maior teor de ligante em relação às misturas sem esta adição. Este fator revela-se bastante importante para as camadas de desgaste drenantes, sendo que um teor de ligante betuminoso mais elevado forma uma película mais espessa em torno dos agregados que aumenta a durabilidade destas misturas.
The increase in rainfall figures over the past decades, in our country and many parts of the world, has been a result of global climate change. The recent increase in the use of porous asphalt, particularly in Europe and the United States of America, is due to its efficiency in controlling runoff and safety on roads. Porous asphalt mixtures are applied to the surface layer of roads due to the many advantages that they bring, such as increased traffic safety during precipitation and noise reduction. Due to its structure with high void content, porous asphalt allows water to be drained and percolated within, being disposed to the side or to appropriate drainage systems adjacent to this layer, which reduces spray effects, increasing the driver’s visibility during periods of rain. However, despite the advantages described above, the application of these layers has some limitations. The major disadvantages of porous asphalt mixtures are clogging and durability. Many of the negative functional effects on the surface result from water damages causing losses in traffic safety and road service level. To improve the quality of porous asphalt much research and several studies have been conducted throughout the world. This dissertation focuses on the assessment of the influence of the action of water in porous asphalt mixtures and the effect of the addition of cellulosic fibers in its composition, comparing its performance with the porous asphalt mixtures without this addition. First, there was its formulation based on bulk density, air voids and particle loss, made through the dry and immerse cantabro particle loss test, obtaining the optimal content of bituminous binder. The evaluation of these mixtures was performed by tests for determining indirect tensile stiffness modulus, water sensitivity and permeability. Through the laboratory work, it was concluded that cellulosic fibers contribute to the improvement of cohesion properties and enhance the porous asphalt mix, allowing an increased binder content compared to the mixtures without this addition. This factor appears to be very important for superficial porous asphalt layers, and a higher content of bituminous binder forms a thicker film that enhances the durability of these mixtures.
The increase in rainfall figures over the past decades, in our country and many parts of the world, has been a result of global climate change. The recent increase in the use of porous asphalt, particularly in Europe and the United States of America, is due to its efficiency in controlling runoff and safety on roads. Porous asphalt mixtures are applied to the surface layer of roads due to the many advantages that they bring, such as increased traffic safety during precipitation and noise reduction. Due to its structure with high void content, porous asphalt allows water to be drained and percolated within, being disposed to the side or to appropriate drainage systems adjacent to this layer, which reduces spray effects, increasing the driver’s visibility during periods of rain. However, despite the advantages described above, the application of these layers has some limitations. The major disadvantages of porous asphalt mixtures are clogging and durability. Many of the negative functional effects on the surface result from water damages causing losses in traffic safety and road service level. To improve the quality of porous asphalt much research and several studies have been conducted throughout the world. This dissertation focuses on the assessment of the influence of the action of water in porous asphalt mixtures and the effect of the addition of cellulosic fibers in its composition, comparing its performance with the porous asphalt mixtures without this addition. First, there was its formulation based on bulk density, air voids and particle loss, made through the dry and immerse cantabro particle loss test, obtaining the optimal content of bituminous binder. The evaluation of these mixtures was performed by tests for determining indirect tensile stiffness modulus, water sensitivity and permeability. Through the laboratory work, it was concluded that cellulosic fibers contribute to the improvement of cohesion properties and enhance the porous asphalt mix, allowing an increased binder content compared to the mixtures without this addition. This factor appears to be very important for superficial porous asphalt layers, and a higher content of bituminous binder forms a thicker film that enhances the durability of these mixtures.
Description
Keywords
Ensaio Cântabro Fibras Celulósicas Mistura Betuminosa Drenante Permeabilidade Sensibilidade à Água.