Asphalt mixtures produced with 100% reclaimed materials

The environmental and economic benefits of using Reclaimed Asphalt Pavement (RAP) material in hot mix asphalt (HMA) applications could be pushed up to the limit, by producing totally recycled HMAs (100% RAP), but the performance of this alternative must be satisfactory. In fact, these mixtures could possibly present a lower performance due to the behaviour of the aged binder, which loses its lighter fractions with time. In order to improve the mixture properties, a binder rejuvenator should be used. Thus, in the present study, the utilization of a used motor oil as a rejuvenator was evaluated. This would allow the modification of the aged binder, restoring some of its original properties and promoting an adequate performance of the mixture. The optimal amount of oil was determined by conventional bitumen tests, using the achievement of a bitumen with a penetration grade above, as the selection criterion for the definition of the amount of oil. Once the amount of rejuvenator (oil) was defined, laboratory specimens were prepared and tested for water sensitivity, permanent deformation, stiffness and fatigue, in order to confirm that the totally recycled mixture will perform as good as a conventional mixture used for comparison purposes.Fundação para a Ciência e a Tecnologia (FCT

Avaliação do desempenho de misturas betuminosas temperadas

A diminuição do consumo de combustíveis e das emissões de gases com efeitos de estufa são um grande desafio da sociedade actual. No fabrico de misturas betuminosas desenvolveram-se recentemente diversas tecnologias para redução da temperatura de produção e aplicação em obra que promoveram a produção de misturas betuminosas temperadas (MBT). Inúmeros benefícios no uso das MBT têm potenciado o seu crescente desenvolvimento, destacando-se a redução das emissões no fabrico e a diminuição do combustível gasto nos queimadores. Na colocação em obra, as MBT garantem uma trabalhabilidade adequada à sua aplicação e compactação a menores temperaturas, reduzindo a produção de fumos, possibilitando o transporte a longas distâncias, alargando a época de pavimentação, e permitindo a sua aplicação a temperaturas atmosféricas inferiores. Neste trabalho compara-se o desempenho mecânico de uma mistura betuminosa (AC 14 Surf 50/70) produzida a temperaturas convencionais e a menores temperaturas (125 a 135 ºC), através da introdução de dois aditivos (Sasobit® e Cecabase®). Foram determinadas as propriedades dos ligantes base e modificados (penetração, anel e bola, viscosidade e reologia) para observação do comportamento, determinação das temperaturas de fabrico e aferição da percentagem de aditivo. A caracterização das misturas foi realizada inicialmente em laboratório (propriedades volumétricas, sensibilidade à água e resistência à deformação permanente), realizando-se em seguida um trecho experimental onde foram extraídos provetes para determinação das características anteriormente referidas, além do módulo de rigidez. Em comparação com a mistura convencional, conseguiu-se reduzir a temperatura das MBT cerca de 15 a 25 ºC mantendo idênticas propriedades volumétricas e mecânicas em laboratório, o que não se conseguiu no trecho devido a um problema de contaminação com o combustível usado no queimador

Evaluation of the rheological behaviour of Warm Mix Asphalt (WMA) modified binders

Several processes and products are available to produce warm mix asphalt (WMA). The use of those may reduce the mixing and compaction temperatures in relation to hot mix asphalt (HMA), ensuring a good performance of the pavement. Lower plant mixing temperatures mean reduction in fuel consumption and lower emissions, what may contribute to diminish odours and health problems. A laboratory study on the properties of the modified binders (using two commercial WMA additives—Sasobit® and Cecabase®) was carried out through conventional (penetration, softening point), dynamic viscosity and rheology (DSR) tests, in order to establish the optimum additive content. Stripping of binder from the aggregates is a reported problem in WMA. Thus, the affinity of the modified binders was assessed without encountering significant problems. It was also observed that only Sasobit® alters the viscosity of the binder. A maximum temperature reduction of 15°C was achieved using 4% of Sasobit® with a softer binder

Indicadores biofísicos de sistemas agroflorestais.

Palestra

Heart rate and blood pressure in mitral valve prolapse patients : divergent effects of long-term propranolol therapy. Correlations with catecholamines

Copyright © 2007 Published by Elsevier Inc.Introduction: There is a well-known association between mitral valve prolapse (MVP) and low blood pressure (BP), although patients (P) often have high levels of catecholamines (CAT) and high heart rate (HR). To our knowledge, there are no studies about the effects of long-term adrenergic b-blockade on these parameters. Methods: Twenty normal individuals (N)—8 males (M) (49.9 F 12.9 years) and 12 females (F) (41.8 F 11.8 years); 46 MVP P—15 M (49.3 F 15.5 years) and 31 F (42.0 F 12.8 years). Phase1—in both N and P free of medication, determination of (1) 24H urinary epinephrine (E) and norepinephrine (NE) by HPLC; (2) rest HR by ECG; (3) 24H ambulatory HR and BP (ABM). Phase2—same tests in MVP P while taking propranolol by 10 to 12 months. Results: CAT ng/mg creatinine: E—M 5.1 F 2.5 (N), 9.1 F 3.9 (Ph1), 7.9 F 3.1 (Ph2); F 6.2 F 3.5 (N), 13.0 F 9.7 (Ph1), 10.7 F 6.7 (Ph2). Higher in P ( P b .01), lower under propranolol ( P = .002). NE—M 22.2 F 7.2 (N), 36.8 F 16.8 (Ph1), 27.4 F 10.6 (Ph2); F 28.1 F 7.3 (N), 46.2 F 18.1 (Ph1), 33.0 F 12.9 (Ph2). Higher in P ( P b .01), lower under propranolol ( P b .001). HR—M 75 F 5.4 (N), 79 F 7.2 (Ph1), 65 F 3.8 (Ph2); F 74 F 3.2 (N), 80 F 6.5 (Ph1), 69 F 6.2 (Ph2). Lower under propranolol ( P b .0001). ABM: phase1—HR higher in P. SBP and DBP lower in P. Phase2—lower HR whereas higher SBP and DBP in P under propranolol. No correlation between BP and CAT. Correlation between E levels and rest HR. Conclusions: These MVP patients had high levels of CAT, high HR, and low BP. With long-term b-blockade, HR decreased related to E, but BP raised, supporting the role of b2 receptors supercoupling on low BP in MVP.info:eu-repo/semantics/publishedVersio

Microstructural evolution of a low-alloy steel / nickel superalloy dissimilar metal weld during post-weld heat treatment

The microstructural evolution of a dissimilar metal weld (DMW) obtained by narrow-gap gas tungsten arc welding (NG-GTAW) was investigated after it was subjected to a post-weld heat treatment (PWHT). The case studied here is a joint between low-alloy steel pipes and a stainless steel steam generator using a nickel based alloy as filler material. The fusion boundary that was the focus of this work was that between the low-alloy steel (2.25Cr-1Mo) and the nickel alloy (alloy 82). The difference in matrix phase and chemical composition between the two alloys leads to a large difference in chemical potential for carbon, which is mobile at the PWHT temperature. A number of advanced characterization techniques were used to assess the gradient of composition, hardness and microstructures across the fusion line, both as welded and after PWHT. This complete analysis permits to highlight and understand the main microstructural changes occurring during the PWHT

Heart rate and blood pressure in mitral valve prolapse patients : divergent effects of long-term propranolol therapy and correlations with catecholamines

Copyright © 2007 The Anatolian Journal of Cardiology.Objective: There is a well known association between mitral valve prolapse (MVP) and low blood pressure (BP), although patients often have high levels of catecholamines and high heart rate (HR). The main objective of our study was to evaluate the effects of long-term adrenergic beta-blockade on these parameters. Methods: The study population consisted of 46 patients with MVP and the control group consisted of 20 normal individuals. The study had two phases: in the first phase, patients were free of medications. In the second phase, patients were under treatment with propranolol for 10 to 12 months. The tests were performed in normal individuals and patients in the first phase. Only patients underwent the same tests in the second phase. Measurement of urinary epinephrine and norepinephrine levels, by high performance liquid chromatography, was done. Rest HR was determined by electrocardiogram (ECG), and ambulatory blood pressure and HR were evaluated by 24 hours ambulatory blood pressure monitoring (ABPM) using the auscultatory method. Results: The levels of epinephrine and norepinephrine were significantly higher in patients than in normal controls and decreased under propranolol. Rest and ambulatory HR were higher in patients and decreased under propranolol. The 24 hours systolic and diastolic BPs were lower in patients, and their values increased under propranolol. Heart rate decreasing and epinephrine levels reduction were positively correlated. No correlation was found between BP increase and catecholamine levels. Conclusion: The study results show divergent effects of propranolol on blood pressure, which increased, and on heart rate, that decreased, in patients with MVP. Heart rate decrease was an expected result and depends, namely, on b1 receptors blockade. Increase in BP is an unusual response to adrenergic beta-blockade in normal conditions, and this finding supports the preponderance of b2 receptors on the BP control in patients with MVP.info:eu-repo/semantics/publishedVersio