Evaluation of fatigue performance at different temperatures

The fatigue performance of asphalt mixtures is used to predict pavement life to control the cracking in the asphalt layers. The design of an asphalt pavement is usually made for a specific temperature, what is intended to represent the pavement behaviour throughout a whole year. For damage analysis during a year, along which the pavement temperature constant-ly varies, it is necessary to calculate the fatigue performance of pavements at a wide range of temperatures. Thus, this paper presents the evaluation of the fatigue response of two asphalt mixtures, a conventional and an asphalt rubber mixture. Frequency sweep tests were also per-formed to evaluate the stiffness modulus. The fatigue test results showed that the fatigue life de-creases when the test temperature decreases up to a certain value. After that value, the fatigue life increases when the test temperature decreases. To explain this phenomenon, this paper presents the preliminary tests carried out to measure the temperature inside the testing speci-mens to verify possible discrepancies between the climatic chamber temperature and the speci-men temperature

An Analysis of the Decay B→D∗XℓνˉℓB \rightarrow D^* X \ell \bar\nu_\ell with Predictions from Heavy Quark and Chiral Symmetry

This paper considers the implications of the heavy quark and chiral symmetries for the semi-leptonic decay $B \rightarrow D^* X \ell \bar \nu_\ell$. The general kinematic analysis for decays of the form {\sl pseudoscalar meson $\rightarrow$ vector meson $+$ pseudoscalar meson $+$ lepton $+$ anti-lepton} is presented. This formalism is applied to the above exclusive decay which allows the differential decay rate to be expressed in a form that is ideally suited for the experimental determination of the different form factors for the process through angular distribution measurements. Heavy quark and chiral symmetry predictions for the form factors are presented, and the differential decay rate is calculated in the kinematic region where chiral perturbation theory is valid.Comment: 15 pages, uses jytex.tex and tables.tex; 3 figures not included but available on reques

Inducing charges and currents from extra dimensions

In a particular variant of Kaluza-Klein theory, the so-called induced-matter theory (IMT), it is shown that any configuration of matter may be geometrically induced from a five-dimensional vacuum space. By using a similar approach we show that any distribution of charges and currents may also be induced from a five-dimensional vacuum space. Whereas in the case of IMT the geometry is Riemannian and the fundamental equations are the five-dimensional Einstein equations in vacuum, here we consider a Minkowskian geometry and the five-dimensional Maxwell equations in vacuum.Comment: 8 pages. Accepted for publication in Modern Physics Letters

Superstatistics, thermodynamics, and fluctuations

A thermodynamic-like formalism is developed for superstatistical systems based on conditional entropies. This theory takes into account large-scale variations of intensive variables of systems in nonequilibrium stationary states. Ordinary thermodynamics is recovered as a special case of the present theory, and corrections to it can be systematically evaluated. A generalization of Einstein's relation for fluctuations is presented using a maximum entropy condition.Comment: 16 pages, no figures. The title changed, some explanations and references added. Accepted for publication in Phys. Rev.

Assessment of stiffness and fatigue tests in Portugal

In the last decade, quality control of asphalt mixtures for pavement construction on the main Portuguese national road network used, most of the time, four-point bending beam tests (4pb) results as a reference. Stiffness modulus and fatigue laws established with samples prepared in the laboratory are usually used as a reference for behaviour/quality control analysis of the samples coming from the construction site. There is however, with this procedure, not only a problem of real world representation but also a question of the compatibility of results coming, again most of the time, from different laboratories using different equipments. Trying to address the second problem, this paper presents the results obtained from four-point bending tests carried out in three different laboratories in Portugal, owning three different 4pb equip-ments, concerning the performance characterization of a typical Portuguese base course asphalt mixture. The paper finally discusses the variability of the results obtained and underlines the main inferences that could be extracted

Improvement of the functional pavement quality with asphalt rubber mixtures

Skid resistance and texture are important safety characteristics which need to be considered in flexible pavement design, maintenance and rehabilitation. The main objective of this paper is to optimize surface texture characteristics in asphalt rubber pavements, mainly macrotexture to reduce splash, spray and hydroplaning and microtexture to increase friction at low and high speeds. The objective was accomplished by measuring the friction surface with two different tests: (i) British pendulum; (ii) Volumetric Method. The specimens prepared in the laboratory represent the as-constructed pavement surface. In this study, two different mixtures grading (dense and gap) were produced using three types of binders: (i) conventional asphalt; (ii) asphalt rubber using terminal blend process; (iii) asphalt rubber using continuous blend process. The binder content influence in functional quality was tested by using the same configuration for mixtures with more 1% of asphalt rubber content. The results of this study were carried out to evaluate the effect of asphalt rubber production process and mixtures gradation on the pavement surface characteristics. The results showed that the mixture with gap grading exhibit higher texture in comparison of mixtures with a dense grade gradation. The asphalt rubber mixtures improved the skid resistance compared to conventional mixtures. This research indicates that the CRM (crumb rubber modified) production with rubber from the different processes have significant differences in pavement surface characteristics.União Europeia (UE) - Programme Alban (E04D040507BR)

Fatigue laws for Brazilians asphalt rubber mixtures obtained in 4 point bending tests

The majority of Brazilian roadpavements consistsof thin pavement structures unable to resist the damage caused by heavy loads and an increasing traffic demand. The main structural distress modes found in Brazilians asphalt layers is fatigue cracking. One of the prom-ising techniques to improve the pavement performance is through asphalt rubber mixtures, which make use of crumb rubber from scrap tires to modify and enhance the properties of the asphalt. The inexistence of fatigue laws for asphalt rubber mixtures to be applied in road design encouraged the study presented in this paper, aiming at the development of prediction models for fatigue and dynamic modulus from the results obtained in laboratory tests. Four mixtures (gap and dense graded) containing Brazilian terminal blend asphalt rubbers were assessed through four point bending tests to evaluate their fatigue and stiffness properties

Desempenho de misturas betuminosas com betume modificado com borracha através do processo húmido

Este trabalho apresenta os resultados da avaliação de desempenho mecânico de misturas betuminosas produzidas com betume modificado com borracha de pneus usados através do processo húmido, utilizando o sistema terminal blend e o sistema continuous blend. Os betumes modificados com borracha através dos dois sistemas foram caracterizados através dos seguintes ensaios: (i) penetração; (ii) ponto de amolecimento (método anel e bola); (iii) resiliência; (iv) viscosidade Brookfield. A avaliação do comportamento mecânico das misturas betuminosas inclui a resistência à fadiga, através do ensaio de flexão em quatro pontos e da deformação permanente utilizando o ensaio de corte simples repetido à altura constante (RSST-CH). Para este estudo foram produzidas misturas betuminosas com dois tipos de granulometria: (i) granulometria densa (Instituto do Asfalto Faixa IV) com betume borracha terminal blend; (ii) granulometria descontínua tipo gap graded (Caltrans ARHM-GG), com betume borracha continuous blend. As misturas com betume borracha foram comparadas com a mistura de referência denominada concreto asfáltico usinado a quente (DNIT 031/2006), preparada com betume convencional. Os resultados mostraram que a mistura com betume modificado com borracha através do sistema terminal blend apresentou o melhor desempenho, com maior vida à fadiga e maior resistência às deformações permanentes.Programa de Bolsas de Alto Nível da União Europeia para a América Latina (Programa ALβAN) - bolsa nº E04D040507BRConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ