1,720,960 research outputs found
Laboratory Study to Evaluate the Influence of Reclaimed Asphalt Content on Performance of Recycled Porous Asphalt
No full textRoad-pavement maintenance and rehabilitation are more frequently performed on porous asphalt (PA) surface layers because of their inherent low durability. Such activities lead to the production of a considerable amount of reclaimed asphalt (RA), mainly from PA layers and from the heavy use of virgin non-renewable natural resources, because of the fact that the use of RA is not usually allowed in PA. In this sense, the use of milled materials from old PA wearing courses in new PA layers promotes an important cycle of re-use that should be encouraged. The experimental study aims to investigate the performance of recycled PA mixtures prepared by partly substituting virgin aggregates with selected coarse RA from a milled PA wearing course. A reference PA mixture (without RA) and six recycled PA mixtures prepared with two amounts of RA (20 % and 25 %) and three total binder contents (5.25 %, 5.50 %, and 5.75 %) were investigated in terms of compactability, durability, and water resistance. In this sense, indirect tensile strength (ITS) tests, particle loss (Cantabro) tests, semicircular bending (SCB) tests, and repeated indirect tensile tests were carried out in both dry and wet conditions. Moreover, compactability properties of the reference PA mixture and the recycled PA mixtures were compared. Results showed that recycled PA mixtures with 20 % and 25 % of RA can perform as well as the reference PA mixture in terms of moisture resistance and durability if an accurate mix design is performed. The optimum total binder content was found to increase as the amount of RA increases, because of the fact that a prominent part of the aged binder acts as "black aggregate." Finally, on the basis of a performance-based equivalence principle, a reliable approach for a practical method able to predict the amount of "re-activated" binder within the RA is proposed
In-plant production of warm recycled mixtures produced with sbs modified bitumen: A case study
No full textAsphalt mixtures produced at reduced temperatures through Warm Mix Additives (WMA) allow reductions of fuel consumption and harmful emissions, ensuring economic and environmental benefits. Considering that nowadays mixtures include more and more often reclaimed aggregates, the combination of recycling and WMA technologies represents a major challenge in road construction and needs further investigations for identifying drawbacks/advantages. Several concerns derive from regular in-plant productions since warm recycled mixtures have been mainly optimized through laboratory studies without evaluating possible issues of large-scale in-plant productions and lay-down processes. So far, few field constructions were realized, limited to small trial sections and without considering the use of modified bitumens. Given this background, the paper describes in-plant productions of warm recycled mixtures prepared with three chemical WMA additives for the construction of an extensive motorway segment. Dense-graded mixtures for binder and base courses as well as open-graded mixtures for wearing courses were produced. Three full-scale trial sections included warm mixtures whereas a further section, used as reference for comparison purposes, comprised analogous mixtures realized through hot recycling according to the current practice. The paper describes the construction steps and the controls carried out to verify technical standard requirements in terms of volumetric properties, compactability and Indirect Tensile Strength. The main objective was to attest the feasibility of large-scale productions to adequately reproduce the mix design previously implemented through laboratory studies when WMA technologies and recycling techniques are concurrently involved. Moreover, gas emissions monitoring at the asphalt plant during the real scale productions was conducted through Continuous Emissions Monitoring Systems in order to quantify the potential benefits in terms of pollution. Results demonstrate the suitability of WMA chemical additives to produce at low temperature mixtures with adequate performance, concurrently recording a significant reduction in pollutants without needing mix design modifications or implementation of expensive new technologies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Use of reclaimed asphalt in porous asphalt mixtures: Laboratory and field evaluations
No full textMaintenance and reconstruction of road pavements involve the production of huge amount of discarded material, such as reclaimed asphalt (RA), every year. As a consequence, issues related to RA stockpiles and disposals are dramatically increasing. At the same time, the growing importance of environmental and economic matters has led researchers and engineers to promote reusing milled materials rather than using valuable and nonrenewable natural resources (bitumen and aggregates). Road pavement maintenance and construction usually involve the use of porous asphalt (PA) mixtures, in particular in the case of motorways and highways. In fact, PA mixtures are widely employed as pavement surface layer thanks to their ability in reducing traffic noise and enhancing safety in wet conditions. In this sense, the reuse of RA into PA should be strongly encouraged. Unfortunately, technical specifications adopted in many countries do not allow any recycled materials in porous asphalt surface layers yet. Thus, reliable techniques allowing the use of RA in new PA mixtures are needed. In this research study, the use of coarse RA from old PA as aggregate in new PA mixtures was evaluated. Because a previous laboratory study demonstrated that the use of 15% of RA aggregates in PA mixtures seems possible (or even recommendable) as long as an accurate mix design with adequate binder contents is performed, new laboratory and field evaluations on recycled PA mixtures with15% of RA aggregates were carried out. On one hand, cyclic coaxial shear tests (CASTs) were performed under both dry and water-submerged conditions in order to evaluate the simultaneous effect of traffic and water exposure. On the other hand, a comprehensive laboratory experimental program for assessing acceptability, durability, fracture resistance, and water sensitivity was carried out on materials taken from the field during the construction of a full-scale trial section. Moreover, drainage properties of surface layers were measured along such a trial section. Overall test results demonstrated that including 15% of selected coarse recycled aggregates into porous asphalt mixtures does not compromise performances and durability of both asphalt-plant and laboratory produced mixtures. It was demonstrated that recycled mixture with 5.25% of total binder content and prepared by accurate mix design can perform as well as (or even better than) standard PA mixture in terms of workability, acceptability, abrasion resistance, repeated loading resistance, fracture propagation resistance, moisture sensitivity, and water drainability
Variations on the Author
Full text link“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
Full text linkWe 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
Improved durability of recycled porous asphalt
No full textPorous asphalt mixtures are extensively used as highway surface layer due to their benefit in improving skid resistance and reducing spray and splash effects during wet conditions. Moreover, porous asphalts (PA) are also oriented towards the reduction of road traffic noise thanks to enhanced sound absorption capabilities. Nevertheless, the limited durability of porous asphalt layers leads to frequent maintenance and rehabilitation activities. In this study, the use of course reclaimed asphalt (RA), obtained by milling old porous surface layers, as aggregate in new PA mixtures was evaluated. Preliminary, Binder Bond Strength tests on coated and uncoated basalt aggregate substrates showed encouraging results in terms of adhesion properties between unaged polymer modified bitumens and substrates coated with aged bitumens, simulating RA aggregates. Thus, five porous asphalt mixtures prepared with 15% course RA aggregates and different total binder contents were studied in the laboratory. A reference PA mixture containing only virgin aggregates was also investigated for comparison purposes. Indirect tensile strength tests, particle loss (Cantabro) tests, semi circular bending (SCB) tests and repeated indirect tensile tests were carried out in both dry and wet conditions in order to evaluate acceptability, durability, fracture resistance and water sensitivity of recycled mixtures. Results showed that recycled porous asphalt mixtures can perform as well as (or even better than) reference one. In particular, recycled mixtures at equal or higher binder contents than the reference mixture demonstrated an improvement in moisture resistance and durability
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
- …
