1,721,059 research outputs found
Monitoring the reduction in shrinkage cracking of mortars containing superabsorbent polymers
Get PDFUltra-high performance concrete (UHPC) is characterized by a low water-to-cement ratio, leading to improved durability and mechanical properties. However, the risk for autogenous shrinkage and cracking due to restrained shrinkage increases, which may affect the durability of UHPC as cracks form pathways for ingress of aggressive liquids and gases. These negative features can be prevented by the use of superabsorbent polymers (SAPs) in the mixture. SAPs reduce autogenous shrinkage by means of internal curing: they will absorb water during the hydration process and release it again to the cementitious matrix when water shortage arises. In this way, hydration can continue and shrinkage is diminished
Early-age monitoring of fresh cementitious material by acoustic emission
Get PDFConcrete properties are mainly affected by the fresh state since it has a significant impact on the long-term concrete
performance. In this study, acoustic emission (AE) was applied to monitor the behavior of fresh cement paste. AE is
based on the detection of high-frequency elastic waves originating from different material sources. This highly
sensitive technique provides data that contribute to a deeper understanding of the different ongoing processes for fresh
concrete, as the possible AE sources are many. Characterization of each different source type is difficult and therefore,
a combined methodology of AE, capillary pressure in the matrix and specimen deformation was applied to monitor
the fresh cement paste
Mitigating autogenous shrinkage by means of superabsorbent polymers : effect on concrete properties
Get PDF(Ultra-)high performance concrete ((U)HPC) is very prone to autogenous shrinkage cracking. These cracks can create preferential pathways for the ingress of harmful substances which can facilitate the corrosion process of the steel reinforcement, resulting in a decreased durability and structural integrity of the concrete structure. Superabsorbent polymers (SAPs) can reduce or even mitigate autogenous shrinkage as they absorb water in the fresh concrete mix and provide it to the cement particles at the right moment in the hydration process, acting as internal curing agent for the concrete. To study the mitigation of autogenous shrinkage by SAPs, five different superabsorbent polymers based on the copolymerization of acrylic acid (AA) with dimethylaminoethyl methacrylate (DMAEMA) were synthesized at Ghent University. This paper focusses on the compatibility tests aiming at evaluating the effect of these SAPs on initial flow and slump life (rheology), hydration kinetics (reactivity) and mechanical properties (3, 7 and 28 days strength). The most promising SAPs will be further studied on their effect to mitigate autogenous shrinkage
Evaluation of the restrained shrinkage cracking potential of self compacting concrete for modulus for radioactive waste disposal
Get PDFFor the disposal of radioactive low- and intermediate-level short-lived waste, surface disposal modules will be built in
Belgium. In order to withstand accidental loading conditions, the walls of these constructions are densely reinforced,
making an implementation in traditional vibrated concrete not self-evident. A Self Compacting Concrete can facilitate this
execution. Questions however exist with regard to the cracking tendency of these concretes against restrained shrinkage,
since this might impair the safety of the radioactive waste disposal. Therefore analyses of restraint shrinkage cracking
potential of two SCC mixtures, especially developed for this application, was conducted within a research project presented
in this paper
Monitoring of fresh concrete by a combined methodology based on stress waves and optical techniques
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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
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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