1,720,956 research outputs found
A preliminary study on the characterization of Recycled Asphalt pavement (RAP)
No full textThe replacement of natural aggregates with recycled ones for concrete production is of vital importance in view of increasing the sustainability of construction materials in accordance with the Circular Economy. The use of crushed Recycled Asphalt Pavement (RAP) as aggregates for concrete will allow the production of more sustainable materials in the construction field. However, chemical, physical and mechanical characteristics of RAP aggregates shall be investigated to optimise their use for concrete production. This issue is one of the tasks of the research project “Sustainable concrete made with recycled asphalt pavement (RAP-CON)” granted by Fondazione Cariplo, currently ongoing.
This study reports the first results on the characterization of five types of RAP collected from different Italian Highways. Several properties of RAP as aggregates for concrete were investigated in terms of microstructure, dimensional stability and durability. In particular, morphological observation was carried out by optical and scanning electron microscopy, while open porosity and pore size distribution was evaluated by mercury intrusion porosimetry. Dimensional stability was assessed by preparing cementitious mortar and concrete samples, following the accelerating curing described in EN 1367-4. Lastly, durability was investigated in terms of resistance to freeze and thaw cycles performed in accordance with EN 1367 (parts 1 and 6) in presence of distilled water and salts (1 wt% NaCl solution), respectively. It was found that RAP is a suitable material for aggregates in concrete. Depending on the adhesion between the bituminous binder and the natural aggregates, different durability performances can be achieved. Finally, different results have been obtained as function of types of RAPs, indicating that their characterization before concrete preparation is an important step to ensure the performance of the final product
Sustainability in Concrete Production: Reclaimed Asphalt Pavement as Recycled Aggregate
No full textIn recent years, scientific research on concrete has focused on the development of sustainable mixes containing recycled materials to avoid the exploitation
of non-renewable resources and to reduce the amounts of landfilled materials. In
this regard, considering that aggregates are the most used material for concrete
production, a virtuous solution may involve the use of recycled ones, such as reclaimed asphalt pavement (RAP). Few studies on RAP as concrete recycled aggregates and their use in concrete production have been already published. Aiming
to fill this gap, a systematic study on the use of RAP to produce more sustainable
concrete is proposed. Firstly, RAP sourced from two Italian collection sites was
characterized as concrete aggregate. Then, microstructure of concrete containing
RAP was studied by mercury intrusion porosimetry (MIP) and scanning electron
microscopy (SEM). Finally, the environmental assessment of concrete containing
RAP and natural aggregate was carried out using a life cycle assessment (LCA)
tool in terms of the global warming potential (GWP) impact category reduction.
Results showed that the well adherent bituminous layer on the aggregate surface
in RAP induces hydrophobic behavior, not evident in natural concrete aggregates.
In hardened concrete containing RAP, an increase in total open porosity and discontinuity in the interface between RAP and cement paste were observed. Finally,
the use of RAP as natural aggregate replacement is a promising route in terms of
sustainability issues, as demonstrated by LCA analysis
Alkali-silica reactions in alkali-activated mortars containing reactive WEEE glasses
No full textThe behaviour of waste glasses from discarded fluorescent lamps (WEEE, waste of electric and electronic equipment) that have been proved extremely reactive in Portland cement composites is evaluated in alkali-activated binders. Metakaolin mixed with sodium hydroxide and sodium silicate is the selected binder. Accelerated test according to ASTM C1260 and longer experiments performed at lower temperature (38°C partially according to ASTM C1293) have been carried out to study the possible reactivity. Moreover, the tests at 80°C have also been performed in calcium hydroxide saturated solution to evaluate the possible effect of calcium ions diffusion in the matrix. In all cases, no clearly expansive gels were formed and consequently the level of expansion is limited
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
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
Performance and environmental analysis of Reclaimed Asphalt Pavement (RAP) concrete produced in industrial environment
No full textThis study aims at evaluating the performances of reclaimed asphalt pavement (RAP) as concrete aggregate replacement in terms of mechanical and physical properties and environmental analysis. RAP concrete production was scaled up and it occurred in an industrial environment (CTI, Imola, Italy) by preparing a 3.5 m3 concrete casting. A partial aggregate replacement of 40% of RAP was fixed to ensure acceptable workability and mechanical performance. For comparison’s sake, the same concrete mix with 100% natural aggregates was also tested. Concrete performances in terms of mechanical and physical properties were checked initially after 7 and 28 days of curing. Environmental analysis of RAP concrete was also carried out using Life Cycle Assessment (LCA) analysis applying a “cradle-to-gate” approach. All the realistic input data collected from the industry plant were considered. Durability tests are ongoing and freezing-thawing resistance and exposure to salt spray chamber on unreinforced and reinforced concrete specimens will be evaluated. As main outcomes, even if inferior mechanical properties were obtained in terms of compressive, tensile strength and elastic modulus values, a relevant reduction (average value of 15%) of environmental impacts was found especially related to global warming potential, terrestrial ecotoxicity, human non- carcinogenic toxicity and fossil resource scarcity. This study is set in the framework of “Sustainable concrete made with recycled asphalt pavement (RAPCON)” project (2020–2023), funded by Cariplo Foundation under the “Circular Economy for a sustainable future” call (2019)
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
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
- …
