Resistência à fadiga de misturas betuminosas com betumes temperados

As problemáticas ambientais que se têm levantado nos últimos anos conduzem a um maior cuidado com o meio ambiente. Para colmatar este facto surgiram, na indústria viária, as misturas betuminosas com betumes temperados que se encontram dentro de um conjunto de novas técnicas que estão a ser desenvolvidas para redução dos consumos, nomeadamente, a poupança de energia e a emissão de gases para a atmosfera, através da diminuição da temperatura de produção. O principal objetivo desta dissertação é estudar o comportamento mecânico de misturas betuminosas produzidas com betumes temperados, com e sem incorporação de material fresado, ao nível da resistência à fadiga. Nestas misturas as temperaturas de produção são inferiores às das misturas betuminosas tradicionais a quente. Esta dissertação inicia com um estado de arte, onde se abordam misturas betuminosas a quente, misturas betuminosas com betumes temperados e misturas com incorporação de material fresado (RAP – Reclaimed Asphalt Pavement), bem como os benefícios a nível social, ambiental e económico. Em seguida, faz-se uma breve abordagem à caracterização da resistência à fadiga de misturas betuminosas, expondo os ensaios mais utilizados. Posteriormente, apresenta-se a metodologia usada para a produção, em laboratório, das misturas betuminosas com diferentes teores de betume para a determinação do teor ótimo de ligante, através da realização de ensaios para a obtenção das propriedades fundamentais. Por último, são realizados ensaios de caracterização, nomeadamente, o ensaio de tração indireta em compressão diametral, o ensaio de sensibilidade à água e o ensaio de flexão em quatro pontos para avaliação da resistência à fadiga das misturas betuminosas. No final, apresentamse as principais conclusões do estudo e propõem-se alguns trabalhos futuros no desenvolvimento deste. Os resultados obtidos mostram que as misturas betuminosas com betumes temperados, com ou sem incorporação de material fresado, apresentam um comportamento mecânico à fadiga muito idêntico às misturas betuminosas a quente. Concluiu-se que as misturas betuminosas temperadas têm um desempenho similar às misturas tradicionais a quente, embora careçam de um cuidado acrescido na fase de produção e aplicação, nomeadamente, no controlo da temperatura de compactação.The environmental issues that have been raised over recent years have led to greater concern with the environment. To address this fact the asphalt industry has developed warm mixasphalt in the context of new technologies that are being developed to reduce energy consumption, in particular saving energy and decreasing gas emissions into the atmosphere, by lowering the mixing temperature. The aim of this dissertation is to study the mechanical behaviour of warm-mix asphalt, with and without incorporation of reclaimed asphalt pavement, at the level of fatigue resistance. In these mixtures, the mixing temperatures are lower than those of the traditional hot-mix asphalt. This dissertation begins with a state of art which addresses hot-mix asphalt, warm-mix asphalt and mixtures with incorporation of reclaimed asphalt pavement, as well as the associated social, environmental and economic benefits. Then, the fatigue resistance of asphalt mixtures is characterised, addressing the most used tests. Subsequently, the methodology used for mixing, in the laboratory, asphalt mixtures with different levels of bitumen content to determine the optimum binder content is presented, by conducting tests in order to obtain fundamental properties. Finally, characterisation tests are performed, namely the indirect tensile stiffness modulus test, the water sensitivity test, and the four point bending test in order to evaluate the fatigue resistance of the asphalt mixtures. In the end, the main conclusions of the study are presented and further research is suggested. The obtained results show that the mechanical fatigue behaviour of warm-mix asphalt, with or without addition of reclaimed asphalt pavement, is very similar to hot-mix asphalt. It was concluded that warm-mix asphalt have a similar performance to traditional hot-mix asphalt, although they require extra care in mixing and placing, in particular, with regard to the control of the compaction temperature

Use of Cellulosic Fibres in Double Layer Porous Asphalt

Climate change, namely precipitation patterns alteration, has led to extreme conditions such as floods and droughts. In turn, excessive construction has led to the waterproofing of the soil, increasing the surface runoff and decreasing the groundwater recharge capacity. The permeable pavements used in areas with low traffic lead to a decrease in the probability of floods peaks occurrence and the sediments reduction and pollutants transport, ensuring rainwater quality improvement. This study aims to evaluate the porous asphalt performance, developed in the laboratory, with addition of cellulosic fibres. One of the main objectives of cellulosic fibres use is to stop binder drainage, preventing its loss during storage and transport. Comparing to the conventional porous asphalt the cellulosic fibres addition improved the porous asphalt performance. The cellulosic fibres allowed the bitumen content increase, enabling retention and better aggregates coating and, consequently, a greater mixture durability. With this solution, it is intended to develop better practices of resilience and adaptation to the extreme climate changes and respond to the sustainability current demands, through the eco-friendly materials use. The mix design was performed for different size aggregates (with fine aggregates – PA1 and with coarse aggregates – PA2). The percentage influence of the fibres to be used was studied. It was observed that overall, the binder drainage decreases as the cellulose fibres percentage increases. It was found that the PA2 mixture obtained most binder drainage relative to PA1 mixture, irrespective of the fibres percentage used. Subsequently, the performance was evaluated through laboratory tests of indirect tensile stiffness modulus, water sensitivity, permeability and permanent deformation. The stiffness modulus for the two mixtures groups (with and without cellulosic fibres) presented very similar values between them. For the water sensitivity test it was observed that porous asphalt containing more fine aggregates are more susceptible to the water presence than mixtures with coarse aggregates. The porous asphalt with coarse aggregates have more air voids which allow water to pass easily leading to ITSR higher values. In the permeability test was observed that asphalt porous without cellulosic fibres presented had lower permeability than asphalt porous with cellulosic fibres. The resistance to permanent deformation results indicates better behaviour of porous asphalt with cellulosic fibres, verifying a bigger rut depth in porous asphalt without cellulosic fibres. In this study, it was observed that porous asphalt with bitumen higher percentages improve the performance to permanent deformation. This fact was only possible due to the bitumen retention by the cellulosic fibres.info:eu-repo/semantics/publishedVersio

Permeable pavements – green infrastructures as a flood mitigation measure

Permeable asphalt pavements have been one of the solutions used to increase the permeability of road pavements given the growing urbanization and climate change. The high porosity and permeability of surface layers with PA (porous asphalt) mixtures allows the water infiltration and, consequently, reduces superficial runoff and contributes to the recharge of underground aquifers. However, the infiltration capacity may be impaired by clogged pores with sediments. The double layer porous asphalt (DLPA) was developed to mitigate this effect. This is a key issue in the pavements’ service life. Information on the clogging processes in these layers is not yet well characterized. The study was carried out using a rainfall simulator in order to generate design storm events with a known intensity and duration. The experimental methodology adopted took into account different phases of evaluation of the infiltration capacity with two clogging cycles (500 and 1000 g m-2). The DLPA infiltration capacity was evaluated in the different phases after different precipitation events (100, 200 and 300 mm h-1). The results showed that, in general, the double layer porous asphalt has the capacity to drain the water, even after clogging and with lower voids content. The infiltration capacity was partially restored when subjected to simple maintenance.info:eu-repo/semantics/publishedVersio

Study of the porous asphalt performance with cellulosic fibres

The porous asphalt (PA) use in road pavements surface layers is one of the most common solutions worldwide to address the climate changes impact like heavy rain. The aim of this study is to evaluate the performance of these mixtures with the cellulosic fibres addition, known for their adherence capacity between the aggregates and the binder. These will help to prevent the binder loss by drainage, which is one of the main problems of porous asphalt, since the fine aggregates content is reduced. Comparing to the conventional porous asphalt the cellulosic fibres addition improved performance to permanent deformation.info:eu-repo/semantics/publishedVersio

Influence of clogging on the hydrologic performance of a double layer porous asphalt

Nowadays, the increasing urbanisation and the effect of climate change in cities has been a constant concern. In particular, the floods cause a significant increase in surface runoff, mostly on roads and parking areas. As an alternative to asphalt pavements, usually used in these areas, permeable pavements have been developed with Porous Asphalt (PA). These pavements allow the infiltration of water from the surface to the ground due to the high void content of the PA, thus reducing the surface runoff and increasing recharge of groundwater. Over the years, the infiltration capacity of the mixtures decreases with the clogging by sediments from the vehicles themselves and/or from the local environment. In order to mitigate this effect, a Double Layer Porous Asphalt (DLPA) was developed. This research intends to deepen the knowledge about the influence of the clogging of a DLPA, with respect to the infiltration capacity, since it is an essential theme in the pavements lifespan and that needs to be developed. This study considered different evaluation phases of the infiltration capacity with two clogging cycles (500 and 1000 g/m2). The materials used were: sand, region soil, and rubber waste. The infiltration capacity test was performed in different phases after a rainfall event of 100 mm/h with a rainfall simulator developed for this purpose. Furthermore, the permeability test with the falling head permeameter was carried out in parallel, obtaining outflow times for each clogging phase and subsequent maintenance phase. The research concluded that DLPA has a high infiltration capacity after the first clogging cycle in both performed tests. In the second clogging cycle, the results show that the infiltration decreased due to the partial filling of the pores, mainly, for the rubber-filled DLPA. The type of clogging material influences the infiltration capacity, nevertheless partially recovered after simple maintenance was performed.info:eu-repo/semantics/publishedVersio

Characterization of the Skid Resistance and Mean Texture Depth in a Permeable Asphalt Pavement

Road pavements need a deep characterization of the surface layer, with which the vehicles have direct contact and, therefore, must provide security to the users. The use of permeable asphalt pavements (PAP) with porous layers has provide obvious advantages in reducing runoff and the rainwater infiltration into the soil or for storage. However, the study of the interaction between the pavement surface layer and the tire rubber requires additional tests in terms of texture and friction, since they are important parameters for the design, construction, management, maintenance and roads safety. Considering the application of a PAP in a parking lot, the study objective was to characterize in the field the pavement surface in terms of mean texture depth (MTD) and skid resistance (Pendulum test value, PTV). The methods used were the volumetric technique by the patch test and the pendulum test, according to EN 13036-1 and EN 13036-4, respectively. The double layer porous asphalt (DLPA) at the surface is characterized by having a structure with high voids content that led to results of clearly rougher macrotexture and good skid resistance. The normalized limit values were met, however, a very strong correlation between MTD and PTV was not observed. A comparison was also made with porous surfaces of other studies and it was found that porous asphalt has a good behaviour at the start of construction which may tend to improve in the long term. From the study, it is concluded that the PAP presents good performance of the surface layer, providing road safety to users.info:eu-repo/semantics/publishedVersio

Permeable asphalt pavement as a measure of urban green infrastructure in the extreme events mitigation

Population growth in cities has led to an increase in the infrastructures construction, including buildings and roadways. This aspect leads directly to the soils waterproofing. In turn, changes in precipitation patterns are developing into higher and more frequent intensities. Thus, these two conjugated aspects decrease the rainwater infiltration into soils and increase the volume of surface runoff. The practice of green and sustainable urban solutions has encouraged research in these areas. The porous asphalt pavement, as a green infrastructure, is part of practical solutions set to address urban challenges related to land use and adaptation to climate change. In this field, permeable pavements with porous asphalt mixtures (PA) have several advantages in terms of reducing the runoff generated by the floods. The porous structure of these pavements, compared to a conventional asphalt pavement, allows the rainwater infiltration in the subsoil, and consequently, the water quality improvement. This green infrastructure solution can be applied in cities, particularly in streets or parking lots to mitigate the floods effects. Over the years, the pores of these pavements can be filled by sediment, reducing their function in the rainwater infiltration. Thus, double layer porous asphalt (DLPA) was developed to mitigate the clogging effect and facilitate the water infiltration into the lower layers. This study intends to deepen the knowledge of the performance of DLPA when subjected to clogging. The experimental methodology consisted on four evaluation phases of the DLPA infiltration capacity submitted to three precipitation events (100, 200 and 300 mm/h) in each phase. The evaluation first phase determined the behavior after DLPA construction. In phases two and three, two 500 g/m2 clogging cycles were performed, totaling a 1000 g/m2 final simulation. Sand with gradation accented in fine particles was used as clogging material. In the last phase, the DLPA was subjected to simple sweeping and vacuuming maintenance. A precipitation simulator, type sprinkler, capable of simulating the real precipitation was developed for this purpose. The main conclusions show that the DLPA has the capacity to drain the water, even after two clogging cycles. The infiltration results of flows lead to an efficient performance of the DPLA in the surface runoff attenuation, since this was not observed in any of the evaluation phases, even at intensities of 200 and 300 mm/h, simulating intense precipitation events. The infiltration capacity under clogging conditions decreased about 7% on average in the three intensities relative to the initial performance that is after construction. However, this was restored when subjected to simple maintenance, recovering the DLPA hydraulic functionality. In summary, the study proved the efficacy of using a DLPA when it retains thicker surface sediments and limits the fine sediments entry to the remaining layers. At the same time, it is guaranteed the rainwater infiltration and the surface runoff reduction and is therefore a viable solution to put into practice in permeable pavements.info:eu-repo/semantics/publishedVersio

Hydraulic Conductivity of the Permeable Asphalt Pavement – Laboratory vs In Situ Test

Permeable asphalt pavements (PAP) are a key measure for mitigating the climate change effects in urban areas. Cities are becoming increasingly dense and have large areas of waterproofing due to the excessive construction of buildings and highways that prevent the rainwater drainage into the soil. Recently, the PAP study with a double layer porous asphalt (DLPA) has been an alternative to the use of a porous asphalt single layer (PA), with recognized advantages in increasing water infiltration and, consequently, in decreasing surface runoff. It was developed in field a PAP of small dimensions to assess its capacity to respond to floods. The purpose of this study is to evaluate the hydraulic conductivity (K) of the DLPA applied on the PAP, both in laboratory conditions and in field conditions, and verify the representativeness of the laboratory results in relation to the results obtained in situ. In laboratory terms, the LCS permeameter was used, which evaluates the vertical and horizontal hydraulic conductivity, both in specimens produced in the laboratory and in cores extracted in situ. In the field, the LCS permeameter and the falling head permeameter were used to measure the hydraulic conductivity and the relative hydraulic conductivity (HC), respectively. The laboratory tests were performed according to Standards EN 12697-19 and NLT 327 and the in situ tests according to Standards EN 12697-40 and NLT 327. It was verified that the specimens produced in the laboratory of the two porous layers showed values of K (vertical and horizontal) lower than those obtained in the field cores, both for the individual layers PA and for the DLPA. Thus, it was found that the study in controlled environment differs in terms of results. This divergence justified the need to perform a field study in order to perceive the actual performance of the PAP surface layer. This study was characterized by the values of K (m/s) and HC (s-1), from which it was not possible to obtain a relation. From this study it was concluded that the measuring methods of the hydraulic conductivity in the laboratory were close to the behaviour of the same in situ, however its evaluation under real conditions is always essential.info:eu-repo/semantics/publishedVersio

Desempenho de misturas recicladas temperadas

Um dos principais desafios que a sociedade enfrenta nos dias de hoje são as preocupações com o meio ambiente sendo um dos objetivos mais procurado a diminuição do consumo de combustíveis fósseis e das emissões para a atmosfera.N/

Formulação e Aplicação

As alterações climáticas têm conduzido a padrões de precipitação mais elevados e frequentes, causando um aumento instantâneo das águas pluviais que acarretam riscos como inundações.N/