1,720,956 research outputs found
The use of Biochar to reduce the carbon footprint of cement-based
Full text linkThe organic waste management is a most current topic, because its processing and degradation it is responsible for emissions of methane and other greenhouse gases, leading to serious environmental problems. Limited oxygen thermochemical processes, such as pyrolysis or gasification, have demonstrated the energy recovery potential of the treated biomass and its environmental benefits. However, the solid part of the process -Biochar- it is considered as a waste, as only its coarse ash can be used as soil improvers. Nevertheless, several researchers have explored its potential application as green filler in order to reduce the carbon footprint both of cement production and cement-based construction materials. In this work, Biochar microparticles were used both as a filler inside the cement paste and mortar composites and as a substitute for the cement powder inside the mixes. Based on previous work, this investigation has a twofold objective: To understand the full influence of the use of an optimized percentage of Biochar (2% with respect to the weight of the cement) either as a filler in the mixture or as a substitute for cement, while guaranteeing an improvement in the strength without losing ductility. The results showed that 2 wt% of Biochar's particles are sufficient to increase the strength and toughness of the cement and mortar composites and, in place of the cement in the mixture, can maintain the mechanical properties equal to those of the reference samples
Mechanical characterization of different biochar-based cement composites
Full text linkThe attention on the use of raw materials, the energy consumption as well as carbon dioxide production of cement factories are boosting the experimentation on innovative and sustainable materials in concrete technology. In recent years, biochar has become an emblematic material with a thousand facets. Mainly investigated up to now as amending in the agricultural field, biochar can be explored as a building material due to its innumerable properties. Indeed, several applications have been studied to use it as a filler to modify the nanogranular nature of the cement matrix, or as a substitute for clinker, aggregates and clay, reducing the carbon footprint and the emissions of greenhouse gases linked to the production processes of cementitious materials. In this paper, nano/micro-particles of biochar, the solid by-product from the gasification process of biomass derived from wood waste, has been used in different cement composites aiming at determining the optimal percentage of addition while trying to guarantee an improvement of mechanical properties. The results showed that an optimized percentage of biochar nano/micro-particles can increase the strength and toughness of the composites
Biochar-based cement pastes and mortars with enhanced mechanical properties
Full text linkNowadays, the environmental impact of cementitious material industry and more generally of building activities is matter of concern, especially in terms of their effects on climate change and consumption of natural resources. Within this context, the aim of this paper is the investigation of the role of biochar, a solid carbonaceous by-product material resulting from biomass pyrolysis/gasification of residual biomass, as a sustainable ingredient for the production of cementitious materials, combining carbon sink properties with enhanced mechanical properties. Although biochar is mainly investigated as agricultural amendment, there is also evidence that biochar may be an eco-friendly material to enhance the sustainable performance of cementitious materials.
As outlined in literature, biochar can be used as filler to modify the nanogranular nature of cement matrix, or as substitute of clinker to reduce the emissions of greenhouse gases related to cement production. In this work, biochar is added as micro-nano particles in different cementitious composites, i.e. cement pastes and mortars, as a function of filler or partial substitute of cement. The main mechanical properties of biochar-based materials are then investigated to determine the optimal percentage of biochar addition
Stability, flexural behavior and compressive strength of ultra-lightweight fiber-reinforced foamed concrete with dry density lower than 100 kg/m3
No full textUltra-lightweight (<100 kg/m3) foamed concrete based on Portland cement was produced by means of preformed foam. The effect of two different protein foaming agents and the addition of polypropylene microfibers on both the fresh and the hardened properties was investigated. In particular, slump, stability, flexural strength, compressive strength, porosity, pore sizes, and distribution were evaluated. The study revealed that the addition of microfibers (5% by mass of cement) gives rise to a three-dimensional system of connection that positively affects stability and mechanical performance. The addition of microfibers gives rise to an increase in flexural strength and compressive strength of approximately 300% and 22% respectively, promoting a ductile behavior, while not compromising workability. Furthermore, the use of a surfactant with higher foaming properties positively affects microstructural pore characteristics, thus enhancing workability and compressive strength. Flexural strength and compressive strength at 28 days of the investigated ultra-lightweight fiber-reinforced foamed concrete are, on average, 0.027 MPa and 0.22 MPa, respectively
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
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
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