bluuebunny/crossref_metadata_2025 huggingface dataset:
Doença celíaca e constipação: uma manifestação clínica atípica e pouco frequente
Authors: Boé Cristiane , Lozinsky Adriana Chebar , Patrício Francy Reis , Andrade Jacy Alves B. de , Fagundes-Neto Ulysses
Published: July 2012

OBJETIVO: Relatar dois casos de doença celíaca (DC) com manifestação de constipação. DESCRIÇÃO DO CASO: Dois pacientes do sexo feminino, com 18 e 30 meses de idade, respectivamente, apresentando história de constipação crônica refratária ao tratamento. Como apresentavam concomitantemente baixo ganho ponderal e estatural, foi realizada investigação da função digestiva-absortiva, que resultou positiva para o anticorpo IgA antitransglutaminase tecidual. O diagnóstico de DC foi confirmado por biópsia de intestino delgado que revelou atrofia vilositária moderada/intensa e infiltrado linfocítico intraepitelial. Um mês após o início do tratamento com dieta isenta de glúten, ambas as pacientes passaram a apresentar fezes pastosas diariamente. COMENTÁRIOS: A DC pode se apresentar nas formas clássica, assintomática e atípica, em que manifestações isoladas como constipação podem retardar o diagnóstico.
Motivação e ensino de espanhol na escola pública paulista: dados quantitativos e qualitativos de um estudo de caso
Authors: Callegari Marília Vasques
Published: July 2012

O presente artigo tem como objetivo apresentar e discutir os resultados de parte de uma pesquisa empírica levada a cabo em 2008 com alunos de espanhol de um dos Centros de Estudos de Línguas mantido pelo governo estadual de São Paulo. Tínhamos como meta conhecer e mensurar, até onde fosse possível, o nível de motivação dos alunos em sala de aula, assim como as suas principais causas. Uma vez que tais Centros são, no momento, os responsáveis em São Paulo pela aplicação da lei que torna obrigatória a oferta de língua espanhola nas escolas de nível médio do país (no que se refere à escola pública estadual), consideramos pertinente divulgar tais resultados, de forma que as discussões suscitadas por eles possam contribuir para um ensino de línguas mais motivador e, portanto, mais eficiente. A pesquisa, de cunho quantitativo e qualitativo, contou com 161 alunos informantes. Os principais resultados apontaram que i) os estudantes em geral encontram-se motivados durante as aulas de espanhol; ii) a figura do professor, o esforço depreendido, o conteúdo, a autonomia de escolha do idioma estudado e o prazer que têm em aprender a LE foram as principais causas de motivação apresentadas; iii) a falta de conhecimento sobre aspectos culturais da língua alvo foi apontada como uma das principais causas de desmotivação; iv) as atividades descritas como mais motivadoras foram, pela ordem, jogos e brincadeiras, vídeos/filmes e músicas; v) as atividades consideradas menos motivadoras foram seminário, prova oral/chamada oral e redação.
Discursos sobre a leitura na contemporaneidade: entre o texto-papel e o texto-tela
Authors: Galli Fernanda Correa Silveira
Published: July 2012

Ancorada na perspectiva teórica da Análise do Discurso, na interface com a Filosofia e as Ciências Sociais, meu propósito, neste artigo, é pensar a circulação dos discursos sobre a leitura na internet. O corpus analisado se constitui de alguns excertos de relatos escritos por alunos de três cursos de graduação do Ensino Superior (Ciências Biológicas, Matemática, Pedagogia), os quais colocam em evidência a produção de discursividades sobre a leitura do texto-papel para o texto-tela, bem como a relação do sujeito-aluno-leitor com as "novas" tecnologias digitais no mundo contemporâneo e globalizado.
A representação social de alunos de escolas da rede particular de ensino acerca do papel do psicólogo escolar
Authors: Carvalho Isaura Santana Costa , Souza Maria Veracy Moreira de
Published: July 2012

Esta pesquisa teve como objetivo compreender a representação social que os alunos de escolas da rede particular de ensino têm acerca do papel do psicólogo escolar. Os dados foram obtidos por meio de entrevistas realizadas com 9 alunos do 7º, 8º e 9º ano. Os resultados colhidos constataram que os alunos percebem o psicólogo escolar basicamente como um profissional que está capacitado a solucionar conflitos. Assim, cabe ao psicólogo escolar delimitar melhor seu campo de atuação para uma melhor compreensão da sua prática profissional.
Behavioral problems and emotional stress in children with bruxism
Authors: Ferreira-Bacci Adriana do Vale , Cardoso Carmen Lúcia Cardoso , Díaz-Serrano Kranya Victoria
Published: July 2012

Bruxism has a multifactorial etiology, and psychosocial factors have been considered to increase the risk of occurrence of this parafunction. The aim of this study was to evaluate the behavior profile of a group of children diagnosed with bruxism. Eighty 7-11-year-old children of both genders (mean age 8.8 years) first recruited as eligible participants. Twenty-nine children (18 males and 11 females) whose parents/guardians reported to present frequent episodes of tooth grinding/clenching while awake or during sleep (at least 3 nights a week) in the previous 3 months were enrolled in the study. The diagnosis of bruxism was established based on the parents/guardians' report about the children's behavior, habits and possible discomforts in the components of the stomatognathic system allied to the presence of signs and symptoms such as pain on the masticatory muscles, masseter muscle hypertrophy, wear facets, fractures of restorations, dental impressions on the cheek mucosa and tongue. As part of the psychological evaluation, the Rutter's Child Behavior Scale-A2 was applied to the parents/caregivers (one for each child) and the Child Stress Scale was applied to the children. Data were analyzed descriptively based on the frequency of each studied variable. Twenty-four (82.76%) children needed psychological or psychiatric intervention; 17 of them presented neurotic disorders and 7 children presented antisocial disorders. Six (20.70%) children presented significant physical and psychological manifestations of stress. The findings of the present study suggest that behavioral problems and potential emotional problems can be risk factors to bruxism in children.
Resistência ao impacto da madeira de nogueira-pecã em diferentes condições de umidade
Authors: Beltrame Rafael , Mattos Bruno Dufau , Gatto Darci Alberto , Lazarotto Marília , Haselein Clovis Roberto , Santini Elio José
Published: July 2012

Os estudos de resistência da madeira ao impacto referem-se à eficiência com que este material absorve energia de um impacto e dissipa-a sem danos a sua estrutura. Dessa forma, o objetivo deste estudo foi avaliar a influência do teor de umidade na resistência ao impacto da madeira de nogueira-pecã (Carya illinoinensis). Para tanto, foram utilizadas árvores procedentes de duas regiões fisiográficas do estado do Rio Grande do Sul. Os corpos de prova, em condições de equilíbrio a 12% de umidade e saturados, foram submetidos ao impacto utilizando-se pêndulo de CHARPY, e avaliados quanto à resistência oferecida com a aplicação da carga nos planos tangencial e radial e posições de retirada (medula - casca) nas toras, para as duas regiões fisiográficas em cada condição de umidade. Para auxiliar na interpretação dos dados, determinou-se a massa específica aparente a 12% e saturada, trabalho absorvido, coeficiente de resiliência e a cota dinâmica. Pôde-se verificar, por meio dos resultados, que a madeira de nogueira-pecã é mais resistente ao impacto na condição saturada.
O processo de trabalho do técnico em saúde bucal e suas relações com a equipe de saúde bucal na Região Metropolitana da Grande Vitória, Espírito Santo, Brasil
Authors: Esposti Carolina Dutra Degli , Oliveira Adauto Emmerich , Santos Neto Edson Theodoro dos , Zandonade Eliana
Published: July 2012

O objetivo deste estudo é analisar a compreensão dos cirurgiões-dentistas (CDs) sobre o processo de trabalho e as relações da equipe de saúde com os Técnicos em Saúde Bucal (TSBs). Em cinco municípios da Região Metropolitana da Grande Vitória (RMGV), Espírito Santo (ES), Brasil, foram selecionados 18 sujeitos, a partir de uma amostra probabilística de 217 CDs que atuavam no Sistema Único de Saúde (SUS). Os sujeitos foram entrevistados a partir de um roteiro-guia semiestruturado, do qual constavam temas relacionados à organização do trabalho na saúde bucal; às atribuições e responsabilidades do TSB; à relação entre o cirurgião-dentista e o TSB; à relação com a equipe de saúde e autonomia do TSB. Os dados foram analisados a partir da Análise de Conteúdo sugerida por Bardin. Constatou-se que os CDs valorizam a importância da participação dos TSBs na reorganização do trabalho odontológico e a construção de uma relação de parceria e cooperação. Contudo, os CDs reconhecem que a relação com os TSBs é prejudicada pela desinformação sobre o processo de trabalho. Além disso, os CDs demonstram receios quanto à possibilidade de os TSBs tornarem-se dentistas práticos e tomarem seu espaço no mercado de trabalho. Também há preocupações sobre a responsabilização legal dos CDs sobre atividades desenvolvidas pelos TSBs.
Contexto, desafios e perspectivas na formação de obstetrizes no Brasil
Authors: Narchi Nádia Zanon , Silva Lúcia Cristina Florentino Pereira da , Gualda Dulce Maria Rosa
Published: July 2012

O artigo descreve o processo de criação do Curso de Obstetrícia da Escola de Artes, Ciências e Humanidades da Universidade de São Paulo. Ele apresenta o projeto político pedagógico e os referenciais teóricos que suportam a formação de obstetrizes, a resistência ou os movimentos que se opõem à formação e ao registro desses profissionais, os desafios que precisam ser superados e, finalmente, as perspectivas nas quais as obstetrizes podem contribuir não só para melhorar a qualidade dos cuidados em saúde, como também para diminuir as taxas de morbidade e mortalidade materna e perinatal e de cesarianas desnecessárias no país.
Advancing teacher knowledge of effective argumentation pedagogy
Authors: Simon Shirley , Davies Paul , Trevethan Jillian
Published: July 2012

This paper provides a discussion of the methodological approach to a research project that builds on previous studies of effective argumentation pedagogy undertaken by one of the authors. In this study, teachers from six schools in a city location are taking part in a one-year project to use new web-based professional development materials to advance their practice in using group discussion and argumentation in science. The teachers attend workshops on planning and organising effective group-work, introducing argument and sustaining small group discussion, and curriculum planning to promote argumentation activity. Between sessions the teachers develop each aspect of pedagogy in their schools. Data are collected from each of the participating schools using teacher survey and interviews to ascertain perspectives on argumentation practice in science, pedagogical strategies used, changes in practice and collaborative working with colleagues in school. The paper focuses on the issues of research design in determining the impact of the workshops.
Inclusão/exclusão escolar e afetividade: repensando o fracasso escolar das crianças de classes populares
Authors: Mattos Sandra Maria Nascimento de
Published: July 2012

A inclusão em educação não se restringe à visão multifacetada da deficiência. Ela se constitui na dialética exclusão/inclusão, fazendo-se parte constitutiva da exclusão. Sabe-se que a antinomia exclusão/inclusão significa o direito à satisfação das necessidades básicas de aprendizagem, a eliminação das barreiras à aprendizagem e a participação de todos no sistema educativo. Entende-se que isso só ocorrerá quando direcionar-se o pensamento para o desenvolvimento de culturas, para a construção de políticas e para a orquestração de práticas inclusivas. Essas três dimensões são necessárias ao (des)envolvimento inclusivo dentro de qualquer escola que pretenda tornar-se inclusiva. O objetivo desse trabalho é mostrar a necessidade de discutir acerca da relação exclusão/inclusão, das diferenças vistas como a especificidade do ser humano e da afetividade, aspecto imprescindível para a aprendizagem. A gestão da afetividade positiva predispõe a ação e a reação em diferentes situações, fazendo com que o aluno "sinta" a aprendizagem, despertando o interesse em aprender e, assim, eliminando o fracasso escolar nas crianças de classes populares. Consequentemente, a tríade afetividade - aprendizagem - inclusão é vital para o processo educativo. Esse trabalho foi concretizado em 2009, em estudos realizados no grupo Laboratório de Pesquisa, Estudos e Apoio à Participação e à Diversidade em Educação - LaPEADE/UFRJ, e tem relação com o período das obras teóricas consultadas e o tema desenvolvido.
Formación y gusto por la escritura y la lectura a luz de las ideas de Friedrich Nietzsche como ámbito de estudio de la Educación Corporal
Authors: García Gutiérrez Carmen Emilia , Correa Castaño Andrés Felipe
Published: July 2012

En este artículo estamos presentando un tema de estudio: la Educación Corporal. Tratamos de leer a Federico Nietzsche a la luz de las ideas de gusto, cuerpo y educación con el interés de abrir horizontes de interpretación para un escenario académico necesitado de una (otra) significación. Recurrimos al pensamiento de Nietzsche con el fin de abordar objetos que él propiamente no llegó a explorar nunca como son la formación del gusto desde el cuerpo en perspectiva pedagógica y hacia una Educación Corporal. Encontramos que los conceptos de formación del gusto y de cuerpo nos sirven como herramientas analíticas para nuestra investigación.
Dialogando com Bakhtin: algumas contribuições para a compreensão das interações verbais no campo da saúde
Authors: Corrêa Guilherme Torres , Ribeiro Victoria Maria Brant
Published: July 2012

Com base na ideia de que as necessidades de, e as intervenções em saúde são condições e ações humanas permeadas e construídas, com frequência, por atos comunicativos, este artigo discute categorias centrais do pensamento do filósofo da linguagem Mikhail Bakhtin tais como: dialogia, enunciado, gênero e polifonia como referencial para a análise de interações verbais no campo da saúde. Bakhtin desenvolve um pensamento cujo fundamento é a natureza social da linguagem, entendendo que a comunicação de cada época e de cada grupo social reflete as condições específicas e as finalidades dos respectivos campos da sociedade. Para ele, o sujeito se constitui discursivamente ao apreender vozes alheias e é integralmente social e singular. Tomando como referência essa constituição social e singular dos indivíduos, o artigo também apresenta, de forma seminal, uma proposição prática para a construção de espaços e de atividades no campo da saúde.
Reabilitação Vestibular em portadores de Vertigem Posicional Paroxística Benigna
Authors: Melo Neto João Simão de , Stroppa Ana Elisa Zuliani , Parrera Carlos Arantes , Maximiano Wilson Franscisco , Hidalgo Cláudia Augusta
Published: July 2012

OBJETIVO: verificar, por meio do questionário handicap de tontura, o efeito de um protocolo de Reabilitação Vestibular (RV) em portadores de Vertigem Posicional Paroxística Benigna (VPPB) sete dias após primeira intervenção e seis meses após a segunda intervenção. MÉTODO: pacientes submetidos à confirmação diagnóstica de VPPB pela positividade da manobra Dix-Hallpike foram avaliados (coleta) pelo questionário Dizziness Handicap Inventory - brasileiro (DHI-brasileiro), antes da primeira intervenção, após a segunda (intervalo de sete dias) e seis meses após a segunda intervenção. As intervenções constavam de relaxamento cervical, manobra de Epley e restrições posturais e foram aplicadas logo após a primeira avaliação e antes da segunda avaliação, com intervalo de sete dias. Os resultados obtidos foram submetidos à análise estatística. RESULTADOS: nove mulheres com média de 63 anos (desvio padrão 4,6) fizeram parte da amostra. Foram encontradas as seguintes pontuações no DHI-brasileiro: Aspecto Físico - apresentou média na coleta 1 de 2,6a(±0,17); coleta 2 de 0,82b (±0,24); coleta 3 de 1,43b(±0,43) com p<0,05; Funcional - apresentou média na coleta 1 de 1,73(±0,21); coleta 2 de 0,93(±0,27); coleta 3 de 1,28 (±0,39); Emocional - apresentou média na coleta 1 de 1,03(±0,24); coleta 2 de 0,49 (±0,23); coleta 3 de 0,82 (±0,36). CONCLUSÃO: a VPPB quando avaliada pelo DHI-brasileiro, traz prejuízos aos portadores em alguns aspectos e a reabilitação vestibular, com a aplicação do protocolo proposto, promoveu melhora na qualidade de vida, com maior redução dos sintomas sete dias após a primeira intervenção. Após seis meses houve certa redução do quadro de melhora, porém este ainda se manteve em melhores condições quando comparado à primeira coleta.
Droga órfã: surgimento de um novo conceito
Authors: Thome-Souza Sigride , Valente Kette D. R.
Published: July 2012

INTRODUÇÃO: A partir de 2007, quatro novas drogas anti-epilépticas foram aprovadas, o acetato de eslicarbazepina, lacosamida, rufinamida e estiripentol. Destas drogas, duas aparecem como drogas órfãs, ou seja, drogas desenvolvidas especificamente para o tratamento de uma síndrome-específica, sendo essas, o estiripentol, indicada na Síndrome de Dravet e a rufinamida, na Síndrome de Lennox-Gastaut. OBJETIVO: Revisar a eficácia, tolerabilidade e efeitos adversos das novas drogas, em especial das drogas órfãs. MÉTODO: Estudos foram selecionados de banco de dados eletrônicos. A análise destes estudos averiguou a eficácia, efetividade, efeitos adversos mais comuns, raros e de longo prazo assim como a comparação com os fármacos existentes. CONCLUSÕES: O desenvolvimento de drogas específicas no tratamento das síndromes epilépticas constitui-se na pedra angular do tratamento da epilepsia, minimizando o tempo até o alcance do controle de crises, com consequente menor tempo de exposição aos efeitos deletérios da epilepsia.
Configuração de arranjos interorganizacionais e implementação de programas públicos
Authors: Barbosa Sheila Cristina Tolentino , Medeiros Janann Joslin
Published: July 2012

A implementação de programas públicos através de relações interorganizacionais envolvendo vários níveis de governo e uma variedade de instituições públicas e privadas é uma tarefa complexa. O desafio é estabelecer de um formato que seja capaz de induzir a ação para o alcance dos resultados planejados. No exame dessa questão, o presente trabalho focaliza o Programa de Alfabetização e Capacitação de Jovens e Adultos de 1998, coordenado pela Superintendência de Desenvolvimento do Nordeste. Utilizando uma metodologia qualitativa para a coleta e análise de dados, o estudo investigou a configuração do arranjo interorganizacional do referido programa. Observou-se que o arranjo adquiriu uma configuração hierárquica, bastante verticalizada, centralizada e pouco interativa tendo como principal conseqüência a inadequação do formato do arranjo para o objetivo proposto. Conclui-se o trabalho tecendo recomendações para a construção de redes interorganizacionais adequadas aos objetivos das ações propostas.
O Tribunal de Contas da União (TCU) e a gestão ambiental brasileira: experiência recente
Authors: Lima Luiz Henrique Moraes de
Published: July 2012

A Constituição de 1988 ampliou a esfera de competência do Tribunal de Contas da União (TCU), assegurando-lhe maior poder de atuação, inclusive na área ambiental. A partir de 1998, com a definição de sua estratégia de atuação nessa área, e de forma crescente, o TCU vem desempenhando um importante papel na avaliação das políticas ambientais públicas do governo federal. A realização de diversas auditorias operacionais em instituições e programas governamentais têm resultado em minuciosos diagnósticos e relevantes recomendações, no sentido de tornar mais efetivas as políticas públicas ambientais. Este estudo descreve e comenta a evolução da fiscalização do TCU sobre a gestão ambiental brasileira nos últimos anos. Também é lembrada a atuação de entidades de fiscalização superiores de outros países na área ambiental. São analisados os critérios da estratégia de atuação ambiental do Tribuna de Contas, bem como as determinações e recomendações de algumas recentes deliberações envolvendo a gestão de recursos hídricos, o licenciamento ambiental e a avaliação ambiental estratégica. Este artigo procura relacionar a atuação do TCU na área ambiental com a busca por um controle preventivo, pedagógico e orientador da gestão pública, em substituição ao tradicional modelo de controle formalista e a posteriori. O artigo conclui que a atuação do tribunal é positiva para a sociedade, recomendando que seja ampliada.
Corrosion of steel reinforcement in carbonated mortar containing chlorides
Authors: Alonso C. , Andrade C.
Published: July 2012

Synopsis

It is well known and accepted that the presence of chlorides and carbonation of the concrete cover are the two main causes of corrosion of reinforcement, and that the simultaneous occurrence of both chlorides and carbonation is expected to increase the likelihood of corrosion. This likelihood may be quantified and monitored through the use of electrochemical techniques.

Polarization resistance and electrochemical impedance measurements on rebars embedded in carbonated mortar containing chlorides have been carried out and the results indicate that these techniques not only allow the extent of corrosion to be estimated but also give information about the effect of the variables on the corrosion process.
A method for predicting alkazi ion concentrations in cement pore solutions
Authors: Taylor H. F. W.
Published: July 2012

Synopsis

A method is described for predicting the sodium, potassium and hydroxyl ion concentrations in the pore solutions ofhydrated OPC or Portland-pfa (pulverized-fuel ash, fly ash) concretes, mortars or pastes more than about 1 day old. The minimum data required are the total Na2O and total K2O contents of the Portland cement component and of the pfa, if present, the relative amounts of Portland cement, pfa and water, and the age. Other data, especially the contents of water-soluble Na2O and K2O in the cement and pfa, may be introduced with advantage. The calculation, which rests on the principle of mass balance combined with empirical equations and constants to represent kinetics and equilibria, may be carried out on a microcomputer. The validity of the results is tested by comparing calculated and observed concentrations for all the cases in which the relevant experimental data were available. Some aspects of the chemistry underlying the method are discussed.
Quantitative analysis of sulphonated melamine formaldehyde superplasticizer in cement
Authors: Yilmaz V. T. , Kindness A. , Glasser F. P.
Published: July 2012

Qualitative identification and quantitative analyses of superplasticizers are conventionally carried out by ultraviolet spectroscopy. This method is satisfactory for solutions of near-neutral pH, but for sulphonated melamine formaldehyde (SMF) materials it is unsatisfactory at higher pH values. In particular, the alkaline nature of cement gives rise to a high concentration of hydroxyl ions and this results in interference. The sample may be neutralized with acid, but this also results in ion interference. Spectrofluorimetry is shown to be a more satisfactory method: it can be used for SMF in solution in either fresh or set cement mixes with only minor pH adjustment. The procedures involved are described and as an example of the application of the method the sorption of SMF on freshly-mixed Portland cement and its hydration products is discussed.
An investigation of the carbonation of cement paste using trimethylsilylation
Authors: Dunster A. M.
Published: July 2012

Ground samples of hydrated cement paste were exposed to atmospheric carbon dioxide and the progress of reaction was monitored by trimethylsilylation of the silicate phases and differential thermal gravimetry (DTG) for calcium hydroxide. The data indicate that carbonation for calcium silicate hydrate (CSH) proceeds via high molecular weight intermediates to give an amorphous hydrous silica material. The carbonation of CSH and calcium hydroxide occurs simultaneously, but a residue of calcium hydroxide carbonates more slowly. This is consistent with a rate-determining stage controlled by the rate of diffusion of carbon dioxide through calcium hydroxide crystals coated with calcium carbonate, and hence also by crystal size.
The hydration of blastfurnace slag cements
Authors: Richardson I. G. , Wilding C. R. , Dickson M. J.
Published: July 2012

A general characterization of the early stage hydration behaviour of ground granulated blastfurnace slag/ordinary Portland cement blends reacting in the temperature range 20–60°C has been made by thermal and electron microscopic techniques. In the blends studied, both the silicate and aluminate associated reactions were accelerated by an increase in hydration temperature, although the aluminate acceleration was greatest. The marked effect of thermal activation on the hydration of ground granulated blastfurnace slag is illustrated.
A comparison between the carbonation of OPC and PFA concrete in a mass concrete structure
Authors: Dunster A. M.
Published: July 2012

The carbonation of an OPC and equivalent PFA concrete (with the same cementitious content) taken from a 30 year old mass concrete buttress dam have been investigated. The results presented compare the determination of the carbonation front made by spraying a freshly broken surface with phenolphthalein, with those determined from calcium hydroxide determination by thermogravimetry (TG), and from the analysis of silicate anions in calcium silicate hydrate (CSH) using trimethylsilylation (TMS). TG and TMS analyses gave similar results for OPC and PFA concrete and indicated in both cases the presence of a carbonating zone of finite width, although the results of using these methods for the OPC concrete showed carbonation to a greater depth than is indicated by phenolphthalein. For the PFA concrete, however, the different methods gave comparable results. Carbonation affected calcium hydroxide and CSH simultaneously within the carbonating zone. A residue of partially carbonated CSH remained in the carbonated zone, indicated by phenolphthalein, although the calcium hydroxide had completely carbonated. It is concluded that the chemical processes of carbonation are very similar for OPC and PFA concrete.
On the kinetics of Portland cement hydration in the presence of selected chemical admixtures
Authors: Chen Y. , Odler I.
Published: July 2012

The complete phase compositIOn of cement pastes prepared from a laboratory-made Portland cement with no admixtures and with added CaCl2 (1·0%), sucrose (0·2 %) and melamine sulphonate resin (1 ·0 %) has been determined between 6 min and 28 days of hydration. Each of the additives affected the hydration progress of the cement, however the hydration kinetics of the individual clinker minerals were altered in different ways.
Impedance studies of wollastonite micro-fibre-reinforced cement paste systems
Authors: Gu Ping , Xu Zhongzi , Xie Ping , Beaudoin J. J. , Low N. M. P.
Published: July 2012

The impedance behaviour of wollastonite micro-fibre-reinforced cement-based composites at various degrees of hydration has been investigated. The observation of larger high-frequency arcs accompanying wollastonite micro-fibre addition to the Portland cement system at a hydration time greater than 3 days is an indication that the fibre matrix interface zone is less porous than the matrix itself. This conclusion is supported by SEM examination and porosimetry determinations. It is demonstrated that differences in the value of R2 (the diameter of the high-frequency arc) for pastes with and without fibre reinforcement can be explained by the contribution to pore structure of both the fibre-cement interface and the cement matrix.
Computer simulation of impedance behaviour in hydrating Portland cement systems
Authors: Gu Ping , Xie Ping , Beaudoin J. J.
Published: July 2012

Computer simulation is applied to reveal the microstructural influence on the impedance behaviour of a hydrating cement paste system. Changes in two major parameters, porosity and mean pore size, have been taken into account in constructing the impedance spectrum. Simulation results show that a decrease in porosity leads to a decrease in both high-frequency resistance R1 and high-frequency arc diameter R2. It has no effect on phase angle shift. A change in mean pore size has a more significant influence than a change in porosity on impedance behaviour, i.e. R1 and R2 of a hydrating cement paste system. It also affects the extent of phase-angle shift.
The chemical reaction in dolomite — KOH solution systems autoclaved at high temperatures
Authors: Min Deng , Qu Wang , Xiaofang Mu , Mingshu Tang
Published: July 2012

The chemical reaction and its rate in a KOH solution—powdered dolostone system at temperatures of 100°C-200°C were investigated by differential thermal analysis, thermogravimetric analysis and X-ray diffraction. It is shown that the reaction is significantly accelerated by increased temperature but the actual mechanism of the reaction, i. e. dedolomitization, is not changed. Calcite, quartz and ilUtic or chloritic clays, which are often found in dolomitic rocks, do not affect the course of the reaction; however, calcite may speed up the dedolomitization.
Neutron radiography: an excellent method of measuring water penetration and moisture distribution in cementitious materials
Authors: Justnes H. , Bryhn-Ingebrigtsen K. , Rosvold G. O.
Published: July 2012

Neutron radiography is an excellent method for determining water penetration or moisture gradients in cementitious materials, since water attenuates thermal neutrons more strongly than the other components (cement, aggregate, etc.), while the opposite is the case for X-rays or gamma radiation. The image of the cross-section of the irradiated area of the sample is transferred indirectly to a photographic film through the β- decay of a dysprosium foil which becomes the primary target of transmitted neutrons. Moisture gradients can then be read from the film by a densiometer or studied in detail by an image processing system. Examples given are the detection of the water front during the capillary suction of water by a cement mortar, a dried concrete core drilled out of an old structure and a sealed cured concrete cast in the laboratory, and a subsequent image analysis of the mortar samples.
C3S hydration in diluted and stirred suspension: (II) properties of C—S—H precipitated during the two kinetic steps
Authors: Damidot D. , Nonat A.
Published: July 2012

The properties of C—S—H formed during the two kinetic steps have been investigated by hydrating mixtures of C3S and C—S—H, in water or saturated lime solutions. C—S—H precipitated during the two kinetic steps (C—S—H(SI) and C—S—H(SII)) have different properties concerning the nucleation rate and the formation of a protective layer around C3S grains. C—S—H(SI) is able to transform into C—S—H(SII) by increasing its C/S ratio when the lime concentration becomes higher than 20 mmol/l. Thus, C—S—H(SI) and C—S—H(SII) may correspond to two different types of C—S—H.
Gypsum of improved performance using blends with Portland cement and silica fume
Authors: Bentur A. , Kovler K. , Goldman A.
Published: July 2012

The present work describes a study intended to develop a blend of gypsum and Portland cement that would possess the advantages of gypsum (high early strength and enhanced workability) and Portland cement (improved durability in moist conditions), but would be free of the deleterious effect of ettringite, which is formed when gypsum and Portland cement interact. This was achieved by preparing a blend of 75% gypsum with a 25% mixture of Portland cement and silica fume. An optimum silica fume—Portland cement ratio of 0·25-0.66 provided a system with strength levels twice as high as those of pure gypsum. The system also exhibited a high wet/dry strength ratio of ∼60 % after 200 days of water immersion. This improvement was explained by the reduction in ettringite formation and the development of a microstructure in which gypsum crystals were engulfed by CSH.
Investigations on ettringite cements
Authors: Odler I , Yan P.
Published: July 2012

Cement pastes were prepared by mixing C3A, CA, C4A3S, C4AF or a CaO-Al2O3-SiO2 glass as Al3+ donor with CaSO4·2H2O, Ca(OH) and water. After curing in completely closed moulds to prevent expansion, the hardened pastes exhibited strength properties comparable with those of other inorganic cements. Ettringite (AFt phase) was formed as the main product of hydration.
C3S hydration in diluted and stirred suspenSIons: (III) NMR study of C-S-H precipitated during the two kinetic steps
Authors: Damidot D. , Nonat A. , Barret P. , Bertrandie D. , Zanni H. , Rassem R.
Published: July 2012

29Si NMR experiments on C-S-H formed during the two kinetic steps of C3S hydration reveal the presence of Q1 and Q2 signals. For a very low percentage of the reaction, a Q0 signal is also observed. However, this signal is not believed to be induced by C-S-H and has been attributed to C3S,h (C3S superficially hydroxylated). Two discontinuities occur when the Q1/Q2 ratio is plotted against the lime concentration in solution. These discontinuities are representative of two invariant points involving three different forms of C-S-H: C-S-H(SO), C-S-H(SI) and C-S-H(SII). C-S-H(SO) and C-S-H(SI) are in equilibrium at the first invariant point and C-S-H(SI) and C-S-H(SII) at the second one. C-S-H(SI) and C-S-H(SII) are precipitated during the first and second kinetic steps respectively, hence the C-S-H precipitated during each kinetic step is different. C-S-H(SO) is not likely to be formed during the hydration of C3S in ‘pure’ water at room temperature.
Changes of C-S-H gel in strong chloride solution
Authors: Kurdowski W. , Duszak S.
Published: July 2012

C-S-H paste was investigated after 28 months' immersion in strong chloride solution with Mg2+. In the outer, altered layer, about 3 mm thick, C-S-H gel became very compact and highly decalcified with a CaO—SiO2 molar ratio (C/S) of 0·48. New phases, brucite and basic magnesium chlorides, were formed, the latter principally in microcracks. In the otherwise unaltered internal zone the concentration of chloride ions was high, being equal to the concentration in the external layer. But the C/S was unchanged and the concentration of magnesium ions was very small, The beginning of the densification process of C-S-H phase can be observed in the transition zone.
Superplasticizers for Ciment Fondu. Part 2: Effects of temperature on the hydration reactions
Authors: Banfill P. F. G.
Published: July 2012

In an investigation of the use of super plasticizers with Ciment Fondu, it was expected that they would have a profound influence on the interactions between temperature, setting time and hydration kinetics. The behaviour of Ciment Fondu in the absence of admixtures has been investigated using conduction calorimetry, supported by setting time measurements. The results confirm that hydration is retarded to the greatest extent at around 30°C, above which progressive acceleration occurs. Applying the Avrami—Erofe'ev equation showed that the maximum rate of heat evolution and the time at which it occurs are reliable kinetic parameters to quantify the hydration rate. In the range 30-45°C the activation energy for hydration is 120 kJ/mol.
Investigation of MgO and CaO/Al2O3 polyphosphate cements
Authors: Walter D. , Odler I.
Published: July 2012

Calcined magnesia and two high-alumina cements, i. e. Secar 51 and Secar 71, were combined with solutions of Na polyphosphate with chain lengths between n = 4 and n = 30. The resulting pastes exhibited setting time and strength development that depended on the poly phosphate chain length and curing conditions. A distinct chemical shrinkage accompanied the hardening process.
Estimation of blastfurnace slag in blended cement by X-ray diffractometry
Authors: Goswami G. , Panigrahy P. K. , Panda J. D.
Published: July 2012

A rapid and accurate method has been developed for estimation of blastfurnace slag (BFS) contents in blended cement by X-ray diffraction (XRD) analysis, based on the ratio between the XRD pulse counts of the cement sample at 20, 30·6 and 22·5 (Cu-Ka). This XRD ratio is found to have an almost linear relationship with the quantity of BFS in the cement. A single set of reference samples may be used for estimation of BFS from different sources, provided both sets have similar physico-chemical characteristics. However, reference samples containing slag from the same source as in the blend improve the accuracy. This method avoids the assumptions or personal judgement involved in some other methods.
The disc-bending point load test for the early strength of hardened cement paste
Authors: Harari Z.
Published: July 2012

A circular disc specimen of finite thickness is freely bottom-supported by a tube that has diameter less than the disc diameter. The specimen is subjected to bending stresses by applying a concentrated load to the centre of its top surface, and the load is increased gradually until the disc fails. A theoretical basis for using this loading configuration as a strength test is derived. This so-called disc-bending point load test is used in this paper for testing the strength of API Class G hardened cement paste specimens of various curing ages. The measured disc-bending point load strength index (Idb) is used for computing the rupture moduli of the test specimens, and for estimating their compressive strengths. The test results are compared with data from conventional strength tests such as the uniaxial compression test, as well as the diametral and axial point load strength tests. Correlations between Idb and uniaxial compressive strength are shown jor disc specimens of various thicknesses, and the effect of indentor penetration and disc thickness is investigated.
Hydration of calcium sulphoaluminate cements
Authors: Lan Wang , Glasser F. P.
Published: July 2012

A range of cements based on calcium sulphoaluminate, 4CaO·3Al2O3·SO3. ‘C4A3S’ are commercially available. The phase contents of some commercial clinkers have been determined. Their hydration behaviour, including calorimetric heat evolutions, are reported. The clinker mineralogies control reactivity and dimensional stability; typically, sulphoaluminate formulations with added lime, gypsum and calcium aluminates are expansive, but those consisting of C4A3S and belite (Ca2SiO4) hydrate rapidly but give rise to dimensionally stable products. The role of accelerating and retarding admixtures is explored. The presence of admixes has a secondary role in controlling the dimensional stability of belite-sulphoaluminate formulations.
Relationship between compressive strength and pore structure of hardened cement pastes
Authors: Takahashi T. , Yamamoto M. , Ioku K. , Goto S.
Published: July 2012

The application of Griffith's theory to the relationship hetween compressive strength and porosity of hardened cement pastes are discussed. Total porosity, compressive strength and the amount of non-evaporable water were measured. The amount of non-evaporable water showed good correlation with the porosity of the hardened cement pastes, and the composition and type of cement had little affect on this relationship. It was clearly shown that the water/cement ratio significantly affected these relationships. It was shown that there were two steps in the development of strength in the function of total porosity: in the early stage of hydration, the development of strength was controlled by maximum pore size: in the later stage, it was controlled by porosity. The effects of porosity and maximum pore size on the strength can be expressed using Griffith's equation, if it can be assumed that the elastic modulus and surface energy are exponential functions of porosity.
Method to evaluate the reactivity of microcrystalline quartz in carbonate rock
Authors: Liang Tong , Meihua Wang , Sufen Han , Mingshu Tang
Published: July 2012

In order to quantify the alkali reactivity of microcrystalline quartz in carbonate rocks, the profile-fitting technique was adopted to analyse its X ray diffraction lines of 20 = 66·5-70° using the FWHM (full width at half maximum) to monitor its crystallinity. It was found that for all the alkali-reactive carbonate rocks tested, silica was present as well-crystallized quartz. so expansion is not due to the alkali-silica reaction (ASR). This evidence supports the suggestion that expansion is caused by reaction between alkali and dolomite, rather than with silica. It is noted that the X ray diffraction method is a powerful means to investigate the reactivity of quartz.
Microstructure and microchemistry of the paste—aggregate interfacial transition zone of high-performance concrete
Authors: Kjellsen K. O. , Wallevik O. H. , Fjällberg L.
Published: July 2012

The microstructure, C-S-H composition and the hydrate distribution of the paste phase, close to aggregates and in the bulk, of mature concretes have been studied. Concrete specimens, and non-concrete specimens in which paste is cast against a piece of aggregate, were studied. At a w/c ratio of 0·40 there exists a marked interfacial transition zone around the aggregate particles showing characteristics such as few un reacted cement grains, little C-S-H, much CH, many hollow shell and, presumably, a relatively high capillary porosity. The microstructural gradient towards the aggregate interface decreases if the w/c ratio is reduced or if the mix contains silica fume. AFm and, presumably, AFt appear to exist both in the bulk phase and in the intelfacial transition zone, apparently without any preference for either of the two phases. The chemical composition of the C-S-H seems to be similar in the interfacial transition zone and in the bulk phase.
Technical note The influence of air entrainment on the properties of silica fume concrete
Authors: Toutanji M.
Published: July 2012

An experimental study on fresh and hardened properties of silica fume concrete containing air-entraining agent was performed. Silica fume content ranged from 0 to 20% by mass of the cementitious materials (cement plus silica fume). Air content in fresh mix concrete ranged between 2 and IS%. Fresh mix properties were characterized by determining the slump and air content. Hardened material properties such as compressive and flexural strength and permeability were investigated. Test results showed that air entrainment reduces the mechanical properties of silica fume concrete. It was also shown that air entrainment has a minimal effect on the permeability of concrete with high silica fume content.
Generalized Bogue computations to forecast the mineralogical composition of sulfoaluminate cements based on fly ashes
Authors: Majling J. , Strigáč J. , Roy D. M.
Published: July 2012

Fly ashes, from an extensive database showing extremes in ratios of major oxides, are considered as potential raw meal ingredients for preparation of sulfoaluminate cements. Simple algorithmized, essentially Bogue-like, computations are performed in order to create a link between the chemical composition of raw meals and their mineralogical composition, as expected to result from their burning. The computations refer to a set of three-component raw meals, all containing limestone and gypsum but differing in the kind of fly ash introduced as the third raw meal component. The individual raw meal compositions are identified in computations, yielding three phase products, composed of C2S, C4A3S; and C4AF. The content of each phase is within the following limits: C2S, 60·7–83·4 wt%; C4AS, 4·2–27·2 wt%; and C4AF 2·67–30·5 wt%. As a result, fly ashes are thus convenient raw sources for production of sulfoaluminate cements. Of special interest are fly ashes low in SiO2/A2O3 or SiO2/(Al2O3 + Fe2O3) ratios, providing clinkers with the preferred proportions of the mineral phases.
Portland cements ground with surfactants
Authors: Teoreanu I. , Guslicov G.
Published: July 2012

The rational use of surfactants based on their effect on the grinding process should also take into consideration the subsidiary effects of surfactants on the handling (flow characteristics) and curing processes (hardening) of the obtained cements. The hardening behaviour of admixed cements on grinding has therefore been investigated with regard to chemical behaviour, that is, the evolution of the hydration process, and structural—mechanical behaviour, that is, the consequent structural evolution of mechanical strength of the hardening cement. Two kinds of cement were used in this investigation; ordinary Portland cement (D) and ferro-Portland cement (M). The surfactants used were dihydroxy compounds (dialcohols and dihydroxy ethers) and aminoalcohols. Information on the fundamental processes that take place on hardening of cements with additives is obtained, in particular their interaction with water and development during hardening, including their mechanical strengths. It was ascertained that the presence of grinding additives influences the kinetics of hydration processes, with delaying effects in the early stages and acceleration of the kinetics subsequently, correlated with the nature of the surfactant. The effects of grinding additives on the microstructure of hardened cements differ according to their nature; among the surfactants used, aminoalcohols and diethylene glycol affect the porosity of hardened cement. Our studies prove that the mechanical strength of hardened cements is a relatively complex result of the effects of grinding additives on both hydration processes and structural development as well as on the proportion of mixing water, and is correlated with the nature of the cement and surfactant.
Effect of PbII and CrVI ions on the hydration of slag alkaline cement and the immobilization of these heavy metal ions
Authors: Cho J. W. , Ioku K. , Goto S.
Published: July 2012

The effect of the curing condition of slag alkaline cement (SAC) on the immobilization of Pb(II) and Cr(VI) ion is discussed. The SAC had properties of rapid and high strength development. The slag hydration products consisted mainly of the gel-like C-S-H phase and silica-alumina gel. The pastes had a high number of very fine pores with a radius of less than 5 nm. This was obtained by autoclaving at a low temperature of 105°C for a very short time (0·5 day). When SAC was autoclaved at temperatures higher than 105°C, the pore radius became wider. When curing at temperatures lower than 105°C, it took longer to obtain the same hydration ratio. Also, the addition of heavy metal ions (Pb(NO3)2 or CrO3 solution) did not affect the hydration of SAC as much. The amount of leached PbII ions was 1·3 × 10−6 mmol/cm2 at 28 days immersion for SAC-NSP pastes (2 mass% Pb(NO3)2 added as PbII ions with sodium silicate solution as an activator) autoclaved at 105°C for 0·5 day. The amount of leached CrVI ions was 6·5 × 10−5 mmol/cm2 at 28 days immersion for SAC-NSC pastes (2 mass% CrO3 added as CrVI ions with sodium silicate solution as an activator) autoclaved at 105°C for 0·5 day. The apparent diffusion coefficient of the CrVI ion had a close relation to the micropore volume. The apparent diffusion coefficient for the CrVI ion in the SAC pastes was about 7·2 × 10−13 cm2/s. SAC pastes was evaluated as an available material for solidifying waste materials.