Predicting pavement evolution is a fundamental component in pavement maintenance and rehabilitati... more Predicting pavement evolution is a fundamental component in pavement maintenance and rehabilitation management work. However, it is very complex to carry out due to several drawbacks, namely a common use of inadequate quality control procedures or a lack of reproducibility of quality control data. This paper describes the main conclusions of a study on the influence of construction quality control data on pavement evolution. It was possible to develop a methodology for this purpose based on stiffness modulus evolution, which will also allow for the assessment of the pavement’s design. The study involved the establishment of a statistical analysis procedure in order to analyse construction quality variability data, and the use of deflection tests, stiffness modulus tests, back-analysis of FWD data and the development of a procedure to correct the effect of temperature within the pavement on stiffness modulus. Results analysis showed that control quality data variability has an import...
This paper seeks to determine the degree of association between selected variables associated to ... more This paper seeks to determine the degree of association between selected variables associated to aspects of road safety (driver, vehicle, road and road environment). The database used consists of accident statistics for roads in Northern Portugal in the period 1999 to 2008. Empirical data analysis using Chi-square testing for association shows that the variables weather conditions, road layout, passengers, pedestrians and driver victims are all associated to the type of accident, although the degree of association is low. The results obtained will be used to develop an accident prediction model for the road network studied. 1. INTRODUCAO A nivel mundial, quando se avaliam os acidentes rodoviarios, conclui-se que a ocorrencia destes eventos depende da contribuicao de multiplos fatores, sendo eles: (i) condutor; (ii) estrada e ambiente viario; (iii) veiculo. Estes fatores agem tanto de forma isolada quanto associados entre si. Ha um consenso sobre a responsabilidade do comportamento d...
Modern noise control policies acknowledge noise abatement at source. As far as traffic noise is c... more Modern noise control policies acknowledge noise abatement at source. As far as traffic noise is concerned, those policies involve the assessment of pavement quality respecting to tyre-road noise and its prevision, like any other pavement performance parameter. This work relies on the Close Proximity method (CPX) to assess tyre-road noise and on complementary tests such as noise absorption, damping and surface texture. Those tests were carried out on several types of pavement surfaces of the national road network. A new approach to tyre-road noise modelling was made with the data through Data Mining techniques. The main results were the assessment of the contribution of each type of surface to traffic noise and the analysis of the relative importance of each variable integrated in the model. It was found that speed is preponderant and damping is significantly more important than the other variables related to texture.
Traffic noise affects greatly health and well-being of people, consequently the knowledge and con... more Traffic noise affects greatly health and well-being of people, consequently the knowledge and control of the factors affecting it is very important. In this study models to predict tyre-pavement noise acoustic and psychoacoustic indicators based on type of pavement, texture, pavement distresses and speed were developed and used to assess the importance of each factor. By applying data mining techniques, in particular artificial neural networks and support vector machines, models with good predictive capacity of both acoustic and psychoacoustic noise indicators were obtained, constituting a precious tool to reduce the tyre-pavement noise. Moreover, the proposed models allowed for the assessment of the influence of the input parameters controlling noise such as: type of pavement, texture, speed and pavement distresses for the first time. It was found that pavement distresses and, as expected, speed influence strongly tyre-pavement noise. In this way it is clearly shown that preventive...
This article intends to be an approach to road network rehabilitation in the context of the new c... more This article intends to be an approach to road network rehabilitation in the context of the new challenges for the near future. Firstly, the current methodology used in the maintenance and rehabilitation and its impact on the pavement life cycle costs is presented. Secondly, the role of innovation at the service of society in the field of road engineering is presented in order to assure a high level of the ride quality, as well as a sustainable construction and rehabilitation of road pavements.
Sound absorption is a material property which contributes to reduce noise levels when sound propa... more Sound absorption is a material property which contributes to reduce noise levels when sound propagates from the source to the receiver. Porous materials have particularly good absorption characteristics, not only because of the high percentage of air voids, but also due to their flow resistance and tortuosity. Road surface layers made of gap graded mixtures are among those absorptive materials. Because these mixtures have a void content that may be considered of medium level, this study aims to characterise their absorption capacity, particularly of those with rubberized asphalt binder. For this purpose, absorption measurements in a Kundt’s tube were performed on cores extracted from slabs with different gap graded asphalt. In order to study the effect of the rubberized asphalt, the mixtures were produced in laboratory with two types of rubberized asphalt and with unmodified asphalt. The effect of the binder was pondered with this procedure. Furthermore, the effect of porosity was c...
FCT – Fundacao para a Ciencia e Tecnologia e contem informacao proveniente dos projetos PEst-OE/E... more FCT – Fundacao para a Ciencia e Tecnologia e contem informacao proveniente dos projetos PEst-OE/ECI/UI4047/2014, PEst-OE/EEI/UI0319/2014 financiados no âmbito do Programa Operacional Tematico Fatores de Competitividade (COMPETE) e comparticipados pelo Fundo Comunitario Europeu FEDER, do projeto PTDC/ECM-TRA 3568/2014 cofinanciado pelo Programa Operacional Competitividade e Internacionalizacao e pelo projeto NORTE-07-0162-FEDER-000076- cave@CCG, ON.2 – Programa Operacional Regional do Norte.
While sound absorption is an acoustic related prope rty reasonably well known and currently used ... more While sound absorption is an acoustic related prope rty reasonably well known and currently used to characterize low noise surfaces, damping is a prope rty commonly used in other domains to define the en ergy dissipation of a material but rarely used to charac terize this important mechanism in road pavements. This paper compares noise related properties such as dam ping and absorption of five road pavement surfaces. Two of which are innovative and therefore expected to b e low noise since they have high voids content, incorporate fine grading aggregates and expanded cl ay. Other two incorporate rubber and waste high-den sity polyethylene giving them an elastic and stiff behav iour respectively. The fifth is a conventional mate rial, asphalt concrete, used for control. Sound absorptio n tests and mechanical impedance tests were carried out in 30x30 cm slabs at 20oC. To measure absorption, an i mpedance tube with an open end was put on the surfaces. To determine damping, the response...
With the pressure to lower traffic noise limits due to environmental impacts, many questions have... more With the pressure to lower traffic noise limits due to environmental impacts, many questions have been raised regarding pedestrians’ safety. Aiming at investigating the effect of traffic noise on crossing behaviour of pedestrians, a virtual environment was reproduced based on data collected from a vehicle passing-by at different speeds and decelerations. In the virtual environment, an experiment with nineteen auditory stimuli was carried out. Eleven participants were asked to signal the moment they thought it was safe to cross the street, without visual information about the car approaching. The Time-to-Collision (TTC) was calculated and compared to the real TTC, to assure that pedestrians’ real vs. virtual crossing behaviour was identical. Afterwards, the crossing rate was calculated and correlated with acoustic and psychoacoustic parameters. Loudness was found to be the best indicator for representing the crossing rate, followed by the maximum sound pressure level (SPLmax). Withou...
O ruido produzido pelo trafego rodoviario, sendo uma componente importante de poluicao ambiental ... more O ruido produzido pelo trafego rodoviario, sendo uma componente importante de poluicao ambiental que afecta significativamente as populacoes, foi incluido no conjunto de indicadores de desempenho dos pavimentos. No entanto, a informacao existente quanto ao impacte ambiental dos diferentes tipos de camadas de desgaste utilizadas correntemente em Portugal e escassa, de modo a nao ser possivel fazerem-se consideracoes ao nivel da gestao dos pavimentos, particularmente no que respeita as estrategias de reabilitacao. Neste artigo faz-se a comparacao do nivel de ruido (Lmax) em diversos pavimentos com camadas de desgaste delgadas adoptadas actualmente na reabilitacao funcional de pavimentos. O nivel de ruido dos veiculos ligeiros e obtido pelos metodos da passagem controlada (CPB) e da proximidade imediata (CPX). A metodologia utilizada foi a preconizada nas normas ISO 11819-1:1997 e ISO CD 11819-2. Em ambos os metodos, as camadas delgadas apresentam niveis de ruido reduzidos relativament...
Noise classification of road surfaces has been addressed in many European countries. This paper p... more Noise classification of road surfaces has been addressed in many European countries. This paper presents the first approach towards noise classification of Portuguese road pavements. In this early stage, it aims at establishing guidelines for decision makers to support their noise reduction policies and the development of a classification system adapted to the European recommendations. A ranking to provide guidance on tire-road noise emission levels for immediate use by decision makers, road authorities, contracting parties and environmental officers will be established. This research was based on the results provided by three early studies covering more than ten different surfaces, among which, rubberized asphalt and experimental non conventional surfaces with optimized grading. On each road trial, the tire-road noise generated by light vehicles and heavy trucks at three speed levels were measured by means of the Controlled Pass-By method (CPB). Three of these runs were also tested...
Wearing course layers with a rubberized asphalt binder have been lately recommended as a measure ... more Wearing course layers with a rubberized asphalt binder have been lately recommended as a measure to mitigate noise. Their acoustical performance in an early age seems to be superior to that shown by conventional layers. Nevertheless, there is no deep knowledge in relation to their behavior throughout their lifetime. The research carried out aims at observing and studying this type of mixes. For this purpose, several road sections with gap-graded mixtures, two of which with rubberized asphalt, were selected. On each road section the tyreroad noise generated by two light vehicles was measured by means of pass-by tests. After three years, those tests were repeated under the same conditions. The results focused on the comparison of the noise level versus speed among layers at the same testing time and on the same layers with different ages. The results obtained three years ago showed that gap-graded asphalt rubber mixtures have a similar performance than that of other type of gap-graded...
This work was financed by FEDER grants through the Operational Competitiveness Program – COMPETE ... more This work was financed by FEDER grants through the Operational Competitiveness Program – COMPETE and ON.2 – Novo Norte (Programa Operacional Regional do Norte 2007/2013) integrated in the structural funds QREN and the project PEst-OE/ECI/UI4047/2014 supported by Portuguese Foundation for Science and Technology.
Normal incidence sound absorption coefficient of materials is usually calculated with the use of ... more Normal incidence sound absorption coefficient of materials is usually calculated with the use of an impedance tube following the ISO 10534-2 international standard. The same is applied in the evaluation of the sound absorption characteristics of pavement mixtures. In this research an impedance tube which was specifically designed to be used in field conditions has been developed. In order test the tube six asphalt slabs were constructed in laboratory and its sound absorption coefficient measured with the new impedance tube. Then, several road sections, with different types of surface, among dense asphalt layers and thin layers, namely with rubberized asphalt were tested. In this paper, some considerations are made regarding the performance of the new impedance tube and the sound absorption coefficient of each asphalt mixtures.
Este trabalho enquadra-se nas atividades do projeto de investigacao AnPeB – Analise do comportame... more Este trabalho enquadra-se nas atividades do projeto de investigacao AnPeB – Analise do comportamento de peoes com base em ambientes simulados e sua incorporacao na modelacao de risco (PTDC/ECM-TRA/3568/2014), foi financiado no âmbito do projeto Promover a Producao Cientifica e Desenvolvimento Tecnologico e a Constituicao de Redes Tematicas (3599-PPCDT) e comparticipado pelo Fundo Comunitario Europeu FEDER. De referir ainda a Fundacao para a Ciencia e a Tecnologia devido ao financiamento da bolsa de doutoramento SFRH/BD/131638/2017.
Traffic noise is an important branch of the environment pollution which deeply affects the popula... more Traffic noise is an important branch of the environment pollution which deeply affects the population and for that reason it has been included in the set of pavement performance indicators. Nevertheless, the knowledge on the environmental impact of the existing surface pavement layers is very limited, particularly for what respects to tyre/road noise of thin layers. These layers are at the present time widely used in a great extent with rubberized asphalt both in urban and rural roads especially in the north of Portugal due to environmental concerns. In this paper the comparison of the tyre/road noise (Lmax) generated in roads with thin surface layers is made. The noise levels generated by light and heavy vehicles are set according to the Statistical Pass-By Method (SPB) of which test methods is described in the standard ISO 11819-1:1997. At management level the information provided by tyre/road noise tests is essential to support environmentally sustainable construction and mainten...
Acoustic absorption properties of materials have often been used to reduce the generation and pro... more Acoustic absorption properties of materials have often been used to reduce the generation and propagation of sound. The research carried out in this paper deals with sound absorption in relation to road surface layers. As the presence of water affects significantly the noise generated by the tyre-road contact, an evaluation of the sound absorption coefficient was made to several wet gap-graded mixtures with different levels of porosity and different contents of rubberized asphalt bitumen. A vacuum device was used to soak the interstices of the cores with water, which were then tested by means of an impedance tube, according with standard ISO 10534-2:1998. It was found that the values of the normal incidence sound absorption coefficient became smeared over the frequency spectrum in comparison with dry samples and that the quantity of rubber in the asphalt bitumen affected the way water fills the cores and, consequently, its sound absorption characteristics.
This paper aims at assessing the relative effect of Portuguese pavement surfaces on traffic noise... more This paper aims at assessing the relative effect of Portuguese pavement surfaces on traffic noise. It presents the main results obtained with two distinct experiments, originally intended for other purposes, which address a significant number of thin layers and porous layers. These experiments included nine road surfaces: three of them were gap graded, three contained rubberized asphalt, one had porous asphalt and two had dense asphalt. On these road sections the tyre-road noise generated by two-axle heavy trucks and three-axle heavy trucks and several light vehicles at three levels of speed were measured by means of pass-by tests. Surface texture tests were also performed. The results focused on noise level variation versus speed and estimated noise level for each speed level versus type of surface. The best performances were achieved by gap graded mixtures with and without rubberized binder and small grain sizes. The fair behaviour shown by the porous asphalt indicates that the su...
Predicting pavement evolution is a fundamental component in pavement maintenance and rehabilitati... more Predicting pavement evolution is a fundamental component in pavement maintenance and rehabilitation management work. However, it is very complex to carry out due to several drawbacks, namely a common use of inadequate quality control procedures or a lack of reproducibility of quality control data. This paper describes the main conclusions of a study on the influence of construction quality control data on pavement evolution. It was possible to develop a methodology for this purpose based on stiffness modulus evolution, which will also allow for the assessment of the pavement’s design. The study involved the establishment of a statistical analysis procedure in order to analyse construction quality variability data, and the use of deflection tests, stiffness modulus tests, back-analysis of FWD data and the development of a procedure to correct the effect of temperature within the pavement on stiffness modulus. Results analysis showed that control quality data variability has an import...
This paper seeks to determine the degree of association between selected variables associated to ... more This paper seeks to determine the degree of association between selected variables associated to aspects of road safety (driver, vehicle, road and road environment). The database used consists of accident statistics for roads in Northern Portugal in the period 1999 to 2008. Empirical data analysis using Chi-square testing for association shows that the variables weather conditions, road layout, passengers, pedestrians and driver victims are all associated to the type of accident, although the degree of association is low. The results obtained will be used to develop an accident prediction model for the road network studied. 1. INTRODUCAO A nivel mundial, quando se avaliam os acidentes rodoviarios, conclui-se que a ocorrencia destes eventos depende da contribuicao de multiplos fatores, sendo eles: (i) condutor; (ii) estrada e ambiente viario; (iii) veiculo. Estes fatores agem tanto de forma isolada quanto associados entre si. Ha um consenso sobre a responsabilidade do comportamento d...
Modern noise control policies acknowledge noise abatement at source. As far as traffic noise is c... more Modern noise control policies acknowledge noise abatement at source. As far as traffic noise is concerned, those policies involve the assessment of pavement quality respecting to tyre-road noise and its prevision, like any other pavement performance parameter. This work relies on the Close Proximity method (CPX) to assess tyre-road noise and on complementary tests such as noise absorption, damping and surface texture. Those tests were carried out on several types of pavement surfaces of the national road network. A new approach to tyre-road noise modelling was made with the data through Data Mining techniques. The main results were the assessment of the contribution of each type of surface to traffic noise and the analysis of the relative importance of each variable integrated in the model. It was found that speed is preponderant and damping is significantly more important than the other variables related to texture.
Traffic noise affects greatly health and well-being of people, consequently the knowledge and con... more Traffic noise affects greatly health and well-being of people, consequently the knowledge and control of the factors affecting it is very important. In this study models to predict tyre-pavement noise acoustic and psychoacoustic indicators based on type of pavement, texture, pavement distresses and speed were developed and used to assess the importance of each factor. By applying data mining techniques, in particular artificial neural networks and support vector machines, models with good predictive capacity of both acoustic and psychoacoustic noise indicators were obtained, constituting a precious tool to reduce the tyre-pavement noise. Moreover, the proposed models allowed for the assessment of the influence of the input parameters controlling noise such as: type of pavement, texture, speed and pavement distresses for the first time. It was found that pavement distresses and, as expected, speed influence strongly tyre-pavement noise. In this way it is clearly shown that preventive...
This article intends to be an approach to road network rehabilitation in the context of the new c... more This article intends to be an approach to road network rehabilitation in the context of the new challenges for the near future. Firstly, the current methodology used in the maintenance and rehabilitation and its impact on the pavement life cycle costs is presented. Secondly, the role of innovation at the service of society in the field of road engineering is presented in order to assure a high level of the ride quality, as well as a sustainable construction and rehabilitation of road pavements.
Sound absorption is a material property which contributes to reduce noise levels when sound propa... more Sound absorption is a material property which contributes to reduce noise levels when sound propagates from the source to the receiver. Porous materials have particularly good absorption characteristics, not only because of the high percentage of air voids, but also due to their flow resistance and tortuosity. Road surface layers made of gap graded mixtures are among those absorptive materials. Because these mixtures have a void content that may be considered of medium level, this study aims to characterise their absorption capacity, particularly of those with rubberized asphalt binder. For this purpose, absorption measurements in a Kundt’s tube were performed on cores extracted from slabs with different gap graded asphalt. In order to study the effect of the rubberized asphalt, the mixtures were produced in laboratory with two types of rubberized asphalt and with unmodified asphalt. The effect of the binder was pondered with this procedure. Furthermore, the effect of porosity was c...
FCT – Fundacao para a Ciencia e Tecnologia e contem informacao proveniente dos projetos PEst-OE/E... more FCT – Fundacao para a Ciencia e Tecnologia e contem informacao proveniente dos projetos PEst-OE/ECI/UI4047/2014, PEst-OE/EEI/UI0319/2014 financiados no âmbito do Programa Operacional Tematico Fatores de Competitividade (COMPETE) e comparticipados pelo Fundo Comunitario Europeu FEDER, do projeto PTDC/ECM-TRA 3568/2014 cofinanciado pelo Programa Operacional Competitividade e Internacionalizacao e pelo projeto NORTE-07-0162-FEDER-000076- cave@CCG, ON.2 – Programa Operacional Regional do Norte.
While sound absorption is an acoustic related prope rty reasonably well known and currently used ... more While sound absorption is an acoustic related prope rty reasonably well known and currently used to characterize low noise surfaces, damping is a prope rty commonly used in other domains to define the en ergy dissipation of a material but rarely used to charac terize this important mechanism in road pavements. This paper compares noise related properties such as dam ping and absorption of five road pavement surfaces. Two of which are innovative and therefore expected to b e low noise since they have high voids content, incorporate fine grading aggregates and expanded cl ay. Other two incorporate rubber and waste high-den sity polyethylene giving them an elastic and stiff behav iour respectively. The fifth is a conventional mate rial, asphalt concrete, used for control. Sound absorptio n tests and mechanical impedance tests were carried out in 30x30 cm slabs at 20oC. To measure absorption, an i mpedance tube with an open end was put on the surfaces. To determine damping, the response...
With the pressure to lower traffic noise limits due to environmental impacts, many questions have... more With the pressure to lower traffic noise limits due to environmental impacts, many questions have been raised regarding pedestrians’ safety. Aiming at investigating the effect of traffic noise on crossing behaviour of pedestrians, a virtual environment was reproduced based on data collected from a vehicle passing-by at different speeds and decelerations. In the virtual environment, an experiment with nineteen auditory stimuli was carried out. Eleven participants were asked to signal the moment they thought it was safe to cross the street, without visual information about the car approaching. The Time-to-Collision (TTC) was calculated and compared to the real TTC, to assure that pedestrians’ real vs. virtual crossing behaviour was identical. Afterwards, the crossing rate was calculated and correlated with acoustic and psychoacoustic parameters. Loudness was found to be the best indicator for representing the crossing rate, followed by the maximum sound pressure level (SPLmax). Withou...
O ruido produzido pelo trafego rodoviario, sendo uma componente importante de poluicao ambiental ... more O ruido produzido pelo trafego rodoviario, sendo uma componente importante de poluicao ambiental que afecta significativamente as populacoes, foi incluido no conjunto de indicadores de desempenho dos pavimentos. No entanto, a informacao existente quanto ao impacte ambiental dos diferentes tipos de camadas de desgaste utilizadas correntemente em Portugal e escassa, de modo a nao ser possivel fazerem-se consideracoes ao nivel da gestao dos pavimentos, particularmente no que respeita as estrategias de reabilitacao. Neste artigo faz-se a comparacao do nivel de ruido (Lmax) em diversos pavimentos com camadas de desgaste delgadas adoptadas actualmente na reabilitacao funcional de pavimentos. O nivel de ruido dos veiculos ligeiros e obtido pelos metodos da passagem controlada (CPB) e da proximidade imediata (CPX). A metodologia utilizada foi a preconizada nas normas ISO 11819-1:1997 e ISO CD 11819-2. Em ambos os metodos, as camadas delgadas apresentam niveis de ruido reduzidos relativament...
Noise classification of road surfaces has been addressed in many European countries. This paper p... more Noise classification of road surfaces has been addressed in many European countries. This paper presents the first approach towards noise classification of Portuguese road pavements. In this early stage, it aims at establishing guidelines for decision makers to support their noise reduction policies and the development of a classification system adapted to the European recommendations. A ranking to provide guidance on tire-road noise emission levels for immediate use by decision makers, road authorities, contracting parties and environmental officers will be established. This research was based on the results provided by three early studies covering more than ten different surfaces, among which, rubberized asphalt and experimental non conventional surfaces with optimized grading. On each road trial, the tire-road noise generated by light vehicles and heavy trucks at three speed levels were measured by means of the Controlled Pass-By method (CPB). Three of these runs were also tested...
Wearing course layers with a rubberized asphalt binder have been lately recommended as a measure ... more Wearing course layers with a rubberized asphalt binder have been lately recommended as a measure to mitigate noise. Their acoustical performance in an early age seems to be superior to that shown by conventional layers. Nevertheless, there is no deep knowledge in relation to their behavior throughout their lifetime. The research carried out aims at observing and studying this type of mixes. For this purpose, several road sections with gap-graded mixtures, two of which with rubberized asphalt, were selected. On each road section the tyreroad noise generated by two light vehicles was measured by means of pass-by tests. After three years, those tests were repeated under the same conditions. The results focused on the comparison of the noise level versus speed among layers at the same testing time and on the same layers with different ages. The results obtained three years ago showed that gap-graded asphalt rubber mixtures have a similar performance than that of other type of gap-graded...
This work was financed by FEDER grants through the Operational Competitiveness Program – COMPETE ... more This work was financed by FEDER grants through the Operational Competitiveness Program – COMPETE and ON.2 – Novo Norte (Programa Operacional Regional do Norte 2007/2013) integrated in the structural funds QREN and the project PEst-OE/ECI/UI4047/2014 supported by Portuguese Foundation for Science and Technology.
Normal incidence sound absorption coefficient of materials is usually calculated with the use of ... more Normal incidence sound absorption coefficient of materials is usually calculated with the use of an impedance tube following the ISO 10534-2 international standard. The same is applied in the evaluation of the sound absorption characteristics of pavement mixtures. In this research an impedance tube which was specifically designed to be used in field conditions has been developed. In order test the tube six asphalt slabs were constructed in laboratory and its sound absorption coefficient measured with the new impedance tube. Then, several road sections, with different types of surface, among dense asphalt layers and thin layers, namely with rubberized asphalt were tested. In this paper, some considerations are made regarding the performance of the new impedance tube and the sound absorption coefficient of each asphalt mixtures.
Este trabalho enquadra-se nas atividades do projeto de investigacao AnPeB – Analise do comportame... more Este trabalho enquadra-se nas atividades do projeto de investigacao AnPeB – Analise do comportamento de peoes com base em ambientes simulados e sua incorporacao na modelacao de risco (PTDC/ECM-TRA/3568/2014), foi financiado no âmbito do projeto Promover a Producao Cientifica e Desenvolvimento Tecnologico e a Constituicao de Redes Tematicas (3599-PPCDT) e comparticipado pelo Fundo Comunitario Europeu FEDER. De referir ainda a Fundacao para a Ciencia e a Tecnologia devido ao financiamento da bolsa de doutoramento SFRH/BD/131638/2017.
Traffic noise is an important branch of the environment pollution which deeply affects the popula... more Traffic noise is an important branch of the environment pollution which deeply affects the population and for that reason it has been included in the set of pavement performance indicators. Nevertheless, the knowledge on the environmental impact of the existing surface pavement layers is very limited, particularly for what respects to tyre/road noise of thin layers. These layers are at the present time widely used in a great extent with rubberized asphalt both in urban and rural roads especially in the north of Portugal due to environmental concerns. In this paper the comparison of the tyre/road noise (Lmax) generated in roads with thin surface layers is made. The noise levels generated by light and heavy vehicles are set according to the Statistical Pass-By Method (SPB) of which test methods is described in the standard ISO 11819-1:1997. At management level the information provided by tyre/road noise tests is essential to support environmentally sustainable construction and mainten...
Acoustic absorption properties of materials have often been used to reduce the generation and pro... more Acoustic absorption properties of materials have often been used to reduce the generation and propagation of sound. The research carried out in this paper deals with sound absorption in relation to road surface layers. As the presence of water affects significantly the noise generated by the tyre-road contact, an evaluation of the sound absorption coefficient was made to several wet gap-graded mixtures with different levels of porosity and different contents of rubberized asphalt bitumen. A vacuum device was used to soak the interstices of the cores with water, which were then tested by means of an impedance tube, according with standard ISO 10534-2:1998. It was found that the values of the normal incidence sound absorption coefficient became smeared over the frequency spectrum in comparison with dry samples and that the quantity of rubber in the asphalt bitumen affected the way water fills the cores and, consequently, its sound absorption characteristics.
This paper aims at assessing the relative effect of Portuguese pavement surfaces on traffic noise... more This paper aims at assessing the relative effect of Portuguese pavement surfaces on traffic noise. It presents the main results obtained with two distinct experiments, originally intended for other purposes, which address a significant number of thin layers and porous layers. These experiments included nine road surfaces: three of them were gap graded, three contained rubberized asphalt, one had porous asphalt and two had dense asphalt. On these road sections the tyre-road noise generated by two-axle heavy trucks and three-axle heavy trucks and several light vehicles at three levels of speed were measured by means of pass-by tests. Surface texture tests were also performed. The results focused on noise level variation versus speed and estimated noise level for each speed level versus type of surface. The best performances were achieved by gap graded mixtures with and without rubberized binder and small grain sizes. The fair behaviour shown by the porous asphalt indicates that the su...
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