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The Circular Economy in the construction sector: enhanced cementitious materials with low CO2 impact.
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Recycling of WEEE plastics waste in mortar: The effects on mechanical properties
Full text linkThis work focused on the recycling of WEEE plastic waste as a partial substitute for aggregate in light mortars. The plastic mix, provided by the IREN group, was used as a replacement of aggregate in 15, 30, 45, 60, 75, and 90%vol in mortars. Worsening of the mechanical performance of around 50% was detected already at only 15%vol of mineral aggregate substituted with plastic waste. The explanation of this phenomenon was found in both the scarce mechanical properties of the used plastic and in the poor adhesion between matrix and plastics that resulted in extra-porosity formation, as also demonstrated by comparing the results with several models in the literature. However, the use of plastic waste as a partial replacement of natural aggregate contributes to the preservation of natural resources and, in any case, does not limit the application of these materials in non-structural applications
Mechanical properties of mortar containing recycled Acanthocardia tuberculata seashells as aggregate partial replacement
Full text linkWaste management is a most current topic, and as such, numerous articles in literature discuss over the recycling and re-use of waste materials from various fields. A common solution is the to use these materials as partial substituent of the inert fraction in concretes and mortars. This work focuses on the possibility of using Acanthocardia tuberculata seashells, which constitute a food waste destined to landfilling, as partial substituents of inert in mortars. The results obtained evidenced that the reduction in mechanical properties (in terms of toughness and flexural stress) is mainly due to the water absorption properties of seashells aggregates, which affect the hydration of the cement. However, as experimentally demonstrated, such decrease in mechanical properties in any case does not compromise the performance of the material when used for civil applications
The influence of biochar shape in cement-based materials
Full text linkBiochar-containing cement composites are gaining interest in the last years due to the possibility of reducing the environmental impact linked to cement. It can also improve the mechanical properties and the electrical conductivity of cement-based materials. A parameter that can affect mechanical performance of biochar-containing cement composites is the morphology of biochar. While it is reasonable to expect a different behavior for different shapes (rod-like, spherical or sheet), a full understanding is yet to be achieved of the competing effects of aspect ratio, morphology, and composition linked to the specific biochar source. This study shows that biochar can improve the mechanical properties of cement-based composites. 1 wt. % of biochar improves of 7 % the compression strength and 15 % the flexural strength. The results presented in this work confirm that biochar has a positive effect on both the mechanical and environmental behavior of cement-based materials
Oxidation of Carbon Nanotubes for Improving the Mechanical and Electrical Properties of Oil-Well Cement-Based Composites
Full text linkCarbon nanotubes are used to improve both the mechanical properties and electrical conductivity of cement, allowing the preparation of a strengthened and toughened cement that can be used for self-monitoring applications. Functionalization by reaction with acid is necessary to guarantee both a good dispersion in water and a strong interaction with cement. Sulfonitric acid (a solution of sulfuric acid and nitric acid) is the best oxidation treatment to decorate the surface of carbon nanotubes with polar groups. The time of treatment influences the mechanical and electrical properties of the composites, and in this work, the effect of the length of the treatment on both CNTs and composites was thoroughly analyzed. It was shown that a long-time oxidation treatment (90 min) was very effective to obtain well-dispersed carbon nanotubes that allow us to obtain cement-based composites with a large improvement of mechanical properties with respect to plain cement: 213% for flexural strength, 90% for fracture energy, and 20% for compressive strength. Furthermore, the electrical resistivity of cement-based composites was reduced to only 3% of the value of plain cement
The Effect of Different Biochar on the Mechanical Properties of Cement-Pastes and Mortars
Full text linkIn recent years, there has been a concerning surge in CO2 emissions, with the construction and materials production sectors standing out as significant contributors to greenhouse gas pollution. To tackle this pressing environmental challenge, architectural design and civil engineering are actively pursuing strategies to mitigate their carbon footprint. These initiatives include adopting eco-friendly construction materials with reduced toxicity, rigorous energy management practices across the entire life cycle of structures, and incorporating innovative materials like biochar. Biochar is a carbon-rich byproduct generated through controlled thermochemical processes, such as pyrolysis or gasification, that stands out for its remarkable capacity to extract energy from processed biomass while delivering substantial environmental advantages. This study examines the use of biochar as a filler in cement-paste and mortar, as well as its influence on mechanical properties. In the case of cementitious pastes, results show that small amounts of biochar (1-2-5% by weight of cement) can improve the compressive and flexural strength, as well as fracture energy, thus generating a more tortuous crack path that increases the final surface area. In mortar specimens, the biochar influence does not show similar patterns or characteristics as the cement-paste in flexural and compressive strengths; nevertheless, biochar particles improve the toughness
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
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