Bibliometric analysis on sustainability in the cement industry/Análise bibliométrica de sustentabilidade na indústria do cimento

The calcination of calcium carbonate, the clinkerization process and the burning of fossil fuels when manufacturing cement are the main culprits of the high CO2 emissions by the cement sector. CO2 is known for being the main greenhouse gas (GHG) and there are growing concerns both nationally and internationally about reducing its emissions. Research on technologies aimed at reducing GHG emissions during the cement manufacturing process can be found in the scientific literature, and include mineral addition, clinker-free cement (or with low clinker content), kiln efficiency, carbon capture, use of raw materials and alternative fuels, among others. The aim of this research was to present a bibliometric analysis of studies on alternatives to reduce greenhouse gas emissions and substitute the use of clinker or cement internationally. The research was based on scientific papers published in renowned journals from 2007 to 2017. Keywords related to CO2 emissions from clinker and cement production were searched for within the vast sustainability area in the Scopus database. The search comprised data on the type of solutions adopted for reducing emissions, the country where the study was conducted, and the number of publications per year and per journal. With the results of this research in hand, the amount of publications from each country was matched with their GHG emission levels. According to the authors, the sustainability of the cement sector depends on reducing kiln energy consumption and clinker consumption in cement, or using less cement in concrete. Moreover, the most widely analyzed impact categories were energy consumption and CO2 emissions, despite the likelihood of other categories having even greater impacts

Effects of command and guided discovery teaching styles on acquisition and retention of the handstand

The influential Mosston’s Spectrum of Teaching Styles is a guide to teaching decisions in Physical Education. This highly researched topic has been tested in many contexts so that our focus is centered on the type of skill during motor skill acquisition in physical education settings. Given that the tasks employed in the studies have been either specialized or manipulative fundamental skills, we sought to extend our understanding of the issue addressing the effects of teaching styles in the process of learning a stability fundamental skill. Our purpose was to examine motor and psychological effects of command and guided discovery teaching styles from Mosston's Spectrum in the acquisition and retention of the handstand in scholars. Third graders from a suburban school in Sao Paulo, Brazil, were assigned to a command (n=22) and a guided discovery (n=23) group. The process of learning the handstand lasted six acquisition sessions, carried out between a pretest and a posttest/retention. We used as dependent variables the motor developmental level (initial, elementary and mature), the movement ratings (scores from 0 to 10) and the motivation levels (post-learning self-reported subscales from the Intrinsic Motivation Inventory). The guided discovery teaching style led more scholars to reach the mature developmental stage of the handstand on retention compared to the command teaching style. No group differences were detected with respect to ratings or intrinsic motivation. Regardless of the group, the pretest ratings were lower than the posttest ones as well as boys scored higher in pressure and tension subscale as compared to girls. The current findings suggest that both teaching styles promoted motor acquisition, but the guided discovery teaching style seemed to yield superior handstand retention

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Carbonation in self-compacting concretes with substitutions of portland cement for mineral additions

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2018.Um concreto autoadensável (CAA) deve ter, simultaneamente, três características: fluidez, coesão e habilidade passante. Sua dosagem exige um maior volume de pasta e de finos, quando comparado ao concreto convencional. O uso de adições minerais no CAA é inevitável para melhorar suas características de autoadensabilidade, além de reduzir o custo de material e possibilitar a incorporação de diversos tipos de resíduos. Normalmente as pesquisas desenvolvidas com a incorporação de adições minerais no concreto autoadensável visam o estudo de propriedades mecânicas desassociadas a questões de durabilidade. Sabe-se que um dos principais mecanismos de despassivação da armadura do concreto estrutural é a carbonatação, que está diretamente ligada à facilidade que o CO2 tem para difundir-se no interior do concreto, às condições ambientais e às propriedades de permeabilidade. Para avaliar a durabilidade frente à ação da carbonatação acelerada do CAA com substituições de cimento Portland por adições minerais, foi realizada a dosagem de seis traços. Como adição mineral, foram escolhidos o fíler calcário e o metacaulim, empregados em substituição a massa de cimento Portland, nas proporções de 10 e 20%, além de um traço com uma combinação ternária entre as adições e o cimento. Avaliou-se o comportamento do concreto no estado fresco, realizando-se os ensaios de espalhamento, caixa L, funil V, índice de estabilidade visual e massa específica, a fim de classificar o CAA conforme os critérios da NBR 15823:2017, além da utilização das equações propostas por Sedran e De Larrard (1999) para determinação dos parâmetros reológicos teóricos. Também foram realizados ensaios no estado endurecido de resistência à compressão simples axial, resistência à tração por compressão diametral, módulo de elasticidade, absorção de água por capilaridade e carbonatação acelerada, este seguindo as recomendações da ISO 1920-12:2015. Os ensaios de porosimetria por intrusão de mercúrio, análise termogravimétrica (TG/DTG) e difração de raios-X foram utilizados para avaliar como as mudanças microestruturais provocadas pelas adições minerais interferem na durabilidade do CAA. Com os parâmetros e critérios de dosagem empregados, foi possível classificar todos os concretos como autoadensáveis. Os traços com a utilização de fíler calcário apresentaram desempenho inferior aos traços que continham metacaulim em todas as propriedades do estado endurecido avaliadas. Segundo as extrapolações realizadas baseadas no cobrimento nominal de 40 mm recomendado pela NBR 6118:2014, dificilmente haveria risco da frente de carbonatação atingir as armaduras de estruturas confeccionadas com algum dos traços estudados. Assim, de um modo geral, o desempenho de todos os traços foi satisfatório, indicando que a utilização de cada um deles é cabível, a depender dos elementos de sua destinação final. O emprego do CAA permitiu a substituição de cimento Portland por adições minerais, e a consequente diminuição do consumo de cimento, sem grandes perdas na trabalhabilidade, nas propriedades mecânicas e na durabilidade frente à carbonatação.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).A self-compacting concrete (SCC) must simultaneously have three characteristics: fluidity, cohesion and passing ability. Its dosage requires a higher volume of paste and fines when compared to conventional concrete. The use of mineral additions in the SCC is inevitable to improve its self-compacting characteristics, reduce material costs and allow the incorporation of different types of waste that would be dumped into the environment, promoting solutions that aim at the sustainable development of the construction sector. Normally the researches developed with the incorporation of mineral additions in the self-compacting concrete aim at the study of mechanical properties disassociated with durability issues. It is known that one of the main mechanisms of depassivation of structural concrete reinforcement is carbonation, which is directly linked to the ease of CO2 diffusion within the concrete, environmental conditions and permeability properties. To evaluate the durability against the action of the accelerated carbonation of SCC with Portland cement substitutions by mineral additions, six types of concrete were measured. As mineral addition, limestone filler and metakaolin were used, replacing the mass of Portland cement in the proportions of 10 and 20%, as well as a concrete with a ternary combination between the additions and the cement. The behavior of the concrete in the fresh state was evaluated by performing the slump flow test, L-box, V-funnel, visual stability index and specific mass in order to classify the SCC according to the criteria of NBR 15823: 2017, besides the use of the equations proposed by Sedran and De Larrard (1999) for the determination of the theoretical rheological parameters. Tests were also carried out in the hardened state of axial compression, tensile strength by diametrical compression, modulus of elasticity, water absorption by capillarity and accelerated carbonation, following the recommendations of ISO 1920-12: 2015. The mercury intrusion porosimetry, thermogravimetric (TG/DTG) and X-ray diffraction tests were used to evaluate how the microstructural changes caused by the mineral additions interfere in the durability of the CAA. With the parameters and dosage criteria employed, it was possible to classify all concrete as self-compacting. The concretes with the use of limestone showed inferior performance to those containing metakaolin in all of the hardened state properties evaluated. According to the extrapolations made based on the nominal 40 mm cover recommended by NBR 6118: 2014, there is hardly any risk of the carbonation front reaching the reinforcement of structures made with any of the studied concretes. Thus, in general, the performance of all the SCC was satisfactory, indicating that the use of each of them is appropriate, depending on the elements of their final destination. The use of the CAA allowed the replacement of Portland cement by mineral additions, and the consequent reduction of cement consumption, without losing the efficiency of workability, mechanical properties and durability against carbonation

Development of a novel viscosity modifier agent for cementitious materials : preliminary study

Concrete compositions demand products in order to meet certain requirements and specific properties. For the production of self-compacting concrete, a certain amount of fine materials and/or chemical products should be added to the mix as viscosity modifying agents that will enable a mixture with enough flowability, and that should show stability. This paper presents preliminary results of a novel viscosity modifying agent based on a biopolymer (chitosan) found in the residues of the fishing industry. The effects of the product were tested in cement pastes by means of typical flow tests and rheological measurements. The new admixture promotes an increase in the plastic viscosity and yield stress of fluid cement pastes resulting in stable and fluid mixtures