1,720,962 research outputs found
A novel method to characterise asphalt binder at high temperature
No full textThe current experimental method used in Europe to characterise asphalt binder at high temperature is based on the Ring & Ball softening point. However, for modified binders it was demonstrated that such a method is unable to correctly characterise the material. In the present work, an alternative solution to determine the high-temperature properties of asphalt binders using the dynamic shear rheometer (DSR) is proposed: the Binder-Fast-Characterisation-Test (BTSV) (Bitumen-Typisierungs-Schnell-Verfahren, in German). Two parameters are identified for the rheological characterisation of asphalt binders: the temperature T-BTSV, which is related to the Ring & Ball softening point and is an indicator of the binder stiffness, and the phase angle delta(BTSV), which provides information on the degree of binder modification. These two key parameters are used to discriminate among the different asphalt binder domains in the high-temperature range
A New Binder-Fast-Characterization-Test Using a Dynamic Shear Rheometer and Its Application for Rejuvenating Reclaimed Asphalt Binder
No full textA simple method using a dynamic shear rheometer is proposed for determining high-temperature key parameters of asphalt binders in place of the ring-and-ball softening point, currently used in Germany. The test was recently introduced in the German standards under the name Bitumen-Typisierungs-Schnell Verfahren (BTSV), which translates to Binder-Fast-Characterization-Test. Two key parameters are obtained as the result of the test: the temperature T-BTSV, at which the shear modulus is equal to 15.0 kPa, and the corresponding phase angle delta(BTSV). While T-BTSV provides information on material hardness, dBTSV indicates the degree of modification. Based on these two parameters, a classification system is proposed for different asphalt binder grades commonly used in Europe. Additionally, the procedure was applied for rejuvenating aged asphalt binder extracted from reclaimed asphalt pavement (RAP). A linear relation is observed for the two key parameters when blending RAP binder with different proportions of rejuvenator. These findings were used to evaluate the effectiveness of different rejuvenating additives
Investigation on the low temperature properties of asphalt binder: Glass transition temperature and modulus shift factor
No full textThis paper investigates the effect of the glass transition temperature, T-g, and the use of modulus shift factors b(T) on the measured rheological properties of asphalt binders at low temperatures. First, temperature-frequency (T-f) sweep tests are performed with the Dynamic Shear Rheometer (DSR) on asphalt binder, and, the corresponding T-g is calculated. Next, modulus shift factors b(T) is applied to the modulus data measured at temperatures below T-g in the Cole-Cole plot. Finally, a visual comparison of master curves and the parameter assessment of 2 Spring 2 Parabolic 1 Dashpot (2S2P1D) model are used to evaluate the effect of b(T). A significant increase in dynamic shear modulus is observed when the DSR test is performed below T-g, while b(T) can take into account this phenomenon on the shape of the curves in the Cole-Cole plot. Hence, the combined use of the horizontal shift factor, a(T), and modulus shift factor, b(T), is recommended when the DSR tests are performed at temperatures lower than the corresponding asphalt binders T-g. (C) 2020 Elsevier Ltd. All rights reserved
Investigation on the Combined Recycling of Reclaimed Asphalt Pavement and Steel Slag in Asphalt Mixture at Low Temperature
No full textIn this paper the effect of the combined use of different amount of Reclaimed Asphalt Pavement (RAP) and Electric Arc Furnace Steel Slag (EAFSS) on the low temperature properties of asphalt mixture is investigated with two experimental methods: Bending Beam Rheometer (BBR) mixture creep and Semi-Circular Bending (SCB) fracture tests. Creep stiffness, m-value, thermal stress, critical cracking temperature, fracture energy and fracture toughness are derived, and then, statistically and graphically compared. The results indicate that mixtures with 100% EAFSS show similar low temperature creep and fracture behavior compared to conventional mixtures, while the presence of RAP results in poorer material performance also when EAFSS is included in the mix design
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Investigation on the Effect of Physical Hardening and Aging Condition on Low-Temperature Properties of Asphalt Binder Based on BBR
No full textLow-temperature properties of asphalt binders are fundamental for designing asphalt mixture in cold regions. This is especially true for alternative technologies such as Warm Mix Asphalt (WMA), for which a temperature reduction during production may potentially lead to substantial benefits in terms of long-term aging conditions. At low temperature, asphalt binder is conventionally characterized based on creep tests conducted with the Bending Beam Rheometer (BBR) in ethanol at a single conditioning time of 1 h. However, asphalt binders undergo significant time-dependent stiffening, often referred to physical hardening, when stored at such low temperatures. In this paper, the effect of aging temperatures and physical hardening on the low temperature rheological properties is experimentally investigated and modeled. First, BBR tests are performed on four long-term aged asphalt binders, which were previously short-term aged at three different temperatures (123 degrees C, 143 degrees C, and 163 degrees C), after three different conditioning times: 1 h, 24 h and 72 h. Next, the creep stiffness, S(t), relaxation parameter, m-value, and difference in critical temperature, Delta T-c are calculated and compared. Finally, the Huet model is fitted to the experimental data with the goal of comparing the effect of aging temperatures and physical hardening on the rheological parameters. Results indicate that physical hardening causes a significant increase in creep stiffness in the first 24 h while only moderate contribution is obtained when condition time is extended. In addition, the reduced production temperature of 40 degrees C can significantly improve the aging properties of asphalt binders at low temperatures while mitigating the effect of physical hardening
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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