Abstract

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES The growing concern with the environment, in recent years, awakens the study of new technologies in the field of paving. Less polluting technologies that minimize the degradation of the environment and that seek to meet sustainability measures are the guiding principle of many researches currently developed. Within this context, pavement recycling emerged as an alternative to reduce the amount of virgin aggregates needed in new pavements, and to reuse this material of great economic value, which was previously deposited on the environment, without adequate reuse. In order to meet the requirements of the Kyoto Protocol of 1997, warm asphalt mixtures have emerged, which have brought a number of benefits when compared to conventional hot mixes, allowing the reduction of the machining and compacting temperatures usually employed, as well as the reduction of consumption decreasing the emission of pollutants and improving the working conditions of operators. Thus, the study of the warm recycled asphalt mixtures begins, which combine the insertion of the recycled pavement material with the technology of the warm mixtures, obtaining an expressive gain in the amount of material to be inserted in new asphalt masses, due to the lower reheating of the milled material. The aim of the present study was to conduct a study on warm recycled asphalt mixtures using conventional binders CAP 50/70 and modified by polymer CAP 60/85. Four asphalt mixtures were studied per binder, between conventional hot mix (reference), warm (no milling), and warm mixtures with 25 and 50% milling (replacing the total mass of virgin aggregates), totaling in eight blends surveyed. After being dosed by the Superpave methodology and analyzed for its volumetric and densification properties, the samples were evaluated for tensile strength (tensile strength by diametral compression and Flow Number), deformability (modulus of resilience and complex modulus) and adhesion and cohesion (Lottman Modified and wear resistance). The main results indicated that the performance of the warm asphalt mixtures is equivalent to the conventional hot mixes. There is also a significant improvement for blends with embedded milling, highlighting the gains obtained in the Flow Number test, which grows significantly as the milling content of the blend increases, as well as the results of adhesion and cohesion through Modified Lottman test, which proved to be positive, probably due to the milling used in the present research to have modified polymer binder (CAP 60/85) in its composition. As for the modified binder mixtures, it is possible to affirm that there is an expressive improvement of performance when compared to the mixtures with conventional binder. A crescente preocupação com o meio ambiente, nos últimos anos, desperta o estudo de novas tecnologias no ramo da pavimentação. Tecnologias menos poluentes, que minimizem a degradação do ambiente e que busquem atender as medidas de sustentabilidade são o fio condutor de muitas pesquisas desenvolvidas atualmente. Dentro deste contexto, a reciclagem de pavimentos surgiu como alternativa de reduzir a quantidade de agregados virgens necessários em novos pavimentos, e reaproveitar esse material de grande valor econômico, que antes era deposto sobre o meio ambiente, sem reutilização adequada. Buscando atender às premissas do Protocolo de Kyoto, de 1997, surgiram as misturas asfálticas mornas, que trouxeram uma série de benefícios, se comparadas às misturas convencionais a quente, permitindo a redução das temperaturas de usinagem e compactação usualmente empregadas, além da redução do consumo energético, diminuição da emissão de poluentes e melhoria nas condições de trabalho dos operadores. Dessa forma, tem início o estudo das misturas asfálticas recicladas mornas, as quais aliam a inserção do material reciclado de pavimento com a tecnologia das misturas mornas, obtendo um ganho expressivo na quantidade de material a ser inserido em novas massas asfálticas, devido ao menor reaquecimento do material fresado. Com esse intuito, o objetivo da presente pesquisa foi realizar um estudo sobre misturas asfálticas recicladas mornas, utilizando ligantes convencional CAP 50/70 e modificado por polímero CAP 60/85. Estudaram-se quatro misturas asfálticas por ligante, entre misturas convencional a quente (referência), morna (sem fresado), e morna com 25 e 50% de fresado (em substituição à massa total de agregados virgens), totalizando em oito misturas pesquisadas. Após dosadas pela metodologia Superpave e analisadas suas propriedades volumétricas e de densificação, as amostras foram avaliadas quanto às propriedades de resistência (resistência à tração por compressão diametral e Flow Number), deformabilidade (módulo de resiliência e módulo complexo) e adesão e coesão (Lottman modificado e resistência ao desgaste cântabro). Os principais resultados apontaram que o desempenho das misturas asfálticas mornas é equivalente às convencionais a quente. Existe também uma melhora significativa para as misturas com fresado incorporado, ressaltando os ganhos obtidos no ensaio de Flow Number, que cresce expressivamente à medida em que se aumenta o teor de fresado da mistura, assim como, os resultados de adesão e coesão, através do ensaio Lottman modificado, que se mostraram positivos, provavelmente, devido ao fresado utilizado na presente pesquisa dispor de ligante envelhecido modificado com polímero (CAP 60/85) em sua composição. Quanto às misturas com ligante modificado, é possível afirmar que existe uma expressiva melhora de desempenho quando comparadas às misturas com ligante convencional.

Abstract

The complexity and severity of contact stresses at the rail-wheel interface coupled with operational conditions of acceleration and braking can lead to the formation of discrete defects such as squats and wheel burns even in the best maintained railway networks. Modern track inspection technologies are deployed for the early detection of such defects to manage the required remedial action to prevent transverse rail breaks. The remedial actions involve either in-situ repair or the replacement of a short length of rail containing the defect. This paper examines the technical and financial imperatives for rail defect repair and details a novel, cost effective, and largely automated low preheat weld restoration technology for the in-situ repair of discrete rail head defects. The paper provides explanation of the science behind the use of low preheat process through instrumented trials to establish the thermal history, metallographic examinations to establish internal integrity, and controlled tests to demonstrate fatigue resistance under cyclic loading. Key findings of the independently audited trial are also summarised.

Abstract

The mechanical recycling of long-fiber reinforced composite materials is presented as an alternative of greater technological simplicity as well as low energy consumption, emission of pollutants and use of solvents, which places it in an advantageous position from the point of view of environmental sustainability. However, the products obtained are short-fibered, which reduces their mechanical reinforcement capability, and have been used mainly as fillers for cementitious, asphalt and thermoplastic matrices.

The technologies used to reduce the size of the initial pieces substantially influence the characteristics of the final product obtained, especially important if they are to be used for functional purposes in terms of electrical or thermal properties. In addition, the fibers obtained have a proportion of resin from the initial composite material, so the subsequent treatment processes of these fibers, both physical and chemical, can affect the amount of final resin present in the product, its agglomeration or its surface characteristics.

The current challenge for these products is to find processes that allow a better quality and greater uniformity of the final properties of the short fiber composites, so that the products obtained present a greater added value, which allows them to compete with other current discontinuous reinforcements.