bluuebunny/crossref_metadata_2025 huggingface dataset:
Estudo epidemiológico de câncer na adolescência em centro de referência
Authors: Presti Paula de Figueiredo , Macedo Carla Renata D. , Caran Eliana Monteiro , Rodrigues Ana Helena D. , Petrilli Antônio Sérgio
Published: July 2012

OBJETIVO: Analisar as características epidemiológicas dos adolescentes portadores de neoplasias encaminhados para o Instituto de Oncologia Pediátrica (IOP/GRAACC) da Universidade Federal de São Paulo, entre os anos de 2000 a 2006. MÉTODOS: Trata-se de um estudo retrospectivo descritivo, em que foram avaliados os dados epidemiológicos dos pacientes, com idade entre dez e19 anos ao diagnóstico, admitidos do ano 2000 a 2006 no IOP/Graacc. RESULTADOS: Do total de 2.362 pacientes admitidos neste período com diagnóstico de câncer, 629 (26,6%) eram adolescentes. A idade média encontrada foi de 13,8 anos, sendo a maioria do sexo masculino (56,8%). Em relação à raça, 60,7% dos pacientes eram brancos. Os tipos de tumores mais frequentes foram: tumores de sistema nervoso central (22,1%), osteossarcoma (14,6%), linfomas (14,5%) e leucemias (14,5%). A sobrevida global, em cinco anos, dos 629 pacientes deste estudo foi de 73,7%. Destaca-se que os adolescentes com rabdomiossarcoma apresentavam doença disseminada e histologia de pior prognóstico, contribuindo para o aumento na taxa de mortalidade deste grupo de pacientes. CONCLUSÕES: Os adolescentes com câncer correspondem a um grupo de pacientes que apresenta características peculiares quando comparado a outros grupos oncológicos. Há diferença histológica dos tumores dos adolescentes com os da infância, em que predominam leucemias e tumores do sistema nervoso central. Nesse contexto, é fundamental facilitar o acesso desses pacientes a centros especializados e oferecer meios apropriados para o diagnóstico precoce e tratamento adequado.
Estágio de prontidão para mudança de comportamento de adolescentes interessados em ingressar no Programa Multiprofissional de Tratamento da Obesidade
Authors: Hintze Luzia Jaeger , Cattai Glauco Barnez P. , Silva Danilo Fernandes da , Nardo Junior Nelson
Published: July 2012

OBJETIVO: Avaliar o estágio de prontidão para mudança do comportamento (EPMC) alimentar e de atividade física de adolescentes e verificar a associação entre as variáveis gênero, faixa etária e classificação do índice de massa corpórea (IMC) com o EPMC. MÉTODOS: Foram avaliados 145 adolescentes entre dez e 18 anos interessados em ingressar no Programa Multiprofissional de Tratamento da Obesidade (PMTO). As avaliações incluíram, além dos EPMC, parâmetros antropométricos. A análise estatística envolveu a aplicação do teste t de Student para amostras independentes e do teste de Mann-Whitney na comparação entre os grupos. O teste do qui-quadrado de tendência foi utilizado para verificar se houve ou não associação entre as variáveis do estudo, sendo significante p<0,05. RESULTADOS: Em relação ao comportamento alimentar (quantidade e tamanho das porções), verificou-se associação entre IMC e o EPMC. Também foi observado que os adolescentes mais velhos apresentaram EPMC mais avançado em relação ao consumo de frutas e verduras. O mesmo se verificou em relação à prática habitual de atividade física. CONCLUSÕES: Há associação entre IMC e o EPMC relacionado ao comportamento alimentar (quantidade e tamanho das porções), do mesmo modo que entre a idade e o EPMC relacionado ao consumo de frutas e vegetais e prática habitual de atividade física. Recomenda-se a realização de estudos experimentais a fim de verificar se o EPMC tem poder preditivo em programas de intervenção destinados ao tratamento do excesso de peso
Educando para transgredir: reflexões sobre o ensino crítico de línguas estrangeiras/inglês
Authors: Urzêda-Freitas Marco Túlio de
Published: July 2012

Neste texto, compartilho algumas reflexões sobre o meu trabalho com o ensino crítico de línguas estrangeiras/inglês no Centro de Línguas da Universidade Federal de Goiás. Teoricamente fundamentado nos pressupostos da Pedagogia Crítica (FREIRE, 2006), dos Estudos Culturais (SILVA, 2007), da Teoria Racial Crítica (FERREIRA, 2006), dos Estudos/Pedagogias Feministas (LOURO, 1997) e da Linguística Aplicada Crítica (PENNYCOOK, 1998, 2001), procuro relacionar o construto pedagogia como transgressão (HOOKS, 1994; PENNYCOOK, 2006) ao ensino de línguas estrangeiras/inglês. Os dados apresentados mostram que o ensino crítico desencadeia muitos conflitos na sala de aula de língua inglesa, mas também evidenciam a sua relevância para o desenvolvimento crítico, linguístico e comunicativo dos(as) alunos(as) e para a formação crítica de professores(as).
Fluxos decisórios na formulação das condicionalidades de saúde do programa bolsa família
Authors: Trevisani Jorginete de Jesus Damião , Burlandy Luciene , Jaime Patricia Constante
Published: July 2012

Os programas de transferência condicionada de renda (TCR) entram na agenda pública por sua potencialidade em interferir no ciclo intergeracional de pobreza. Este artigo tem como objetivo analisar o processo de formulação das condicionalidades de saúde do Programa Bolsa Família e, secundariamente, avaliar sua interface com a trajetória das políticas de alimentação e nutrição no Brasil. Para isso, o estudo adotou como referencial analítico o modelo de análise de múltiplos fluxos, proposto por Kingdon, para quem a mudança na agenda pública acontece com a convergência entre o fluxo dos problemas, o fluxo das soluções e alternativas e o fluxo político. A trajetória desses fluxos foi recomposta por meio da análise de documentos governamentais e de relatos orais obtidos por meio de entrevistas. No momento da formulação das condicionalidades de saúde, no fluxo de problemas, havia a necessidade de mudar a estratégia de combate à desnutrição, devido às críticas ao Incentivo ao Combate às Carências Nutricionais (ICCN) e à extinção do Programa de Distribuição de Estoques de Alimentos (PRODEA). No que diz respeito ao fluxo das soluções, diversas propostas de TCR estavam em curso. No fluxo político, havia a decisão de criação de uma rede de proteção social. Nesse processo, a Coordenação Geral da Política de Alimentação e Nutrição assumiu o papel de empreendedora de políticas. A reflexão sobre esse processo ajuda a compreender o papel dos serviços de saúde em um programa de caráter intersetorial.
Aconselhamento em DST/Aids às gestantes que realizaram o teste anti-HIV na admissão para o parto: os sentidos de uma prática
Authors: Fonseca Patrícia de Lima , Iriart Jorge Alberto Bernstein
Published: July 2012

Foram analisadas as práticas e os sentidos do aconselhamento para gestantes submetidas ao teste anti-HIV na admissão para o parto, e para profissionais de saúde que atuam na assistência à maternidade em Salvador, Brasil. Foi realizado um estudo qualitativo em uma maternidade, com observação participante e entrevistas semiestruturadas com 13 puérperas sem diagnóstico prévio para o HIV e sete profissionais de saúde. Observou-se que o exame anti-HIV é realizado de forma compulsória, sem considerar a autonomia da gestante, e que o aconselhamento se limita a informar o diagnóstico e dar orientações no pós-teste somente àquelas cujos resultados foram positivos. Os sentidos que permeiam o exame, assim como o entendimento da experiência e os significados construídos pelas puérperas, sobretudo quando se descobrem positivas para o HIV, não são abordados pelos profissionais, que não se sentem capacitados para acolherem a subjetividade das pacientes.
Testigos modestos y poblaciones invisibles en la cobertura de la genética humana en los medios de comunicación colombianos
Authors: Díaz del Castillo Adriana , Olarte Sierra María Fernanda , Pérez-Bustos Tania
Published: July 2012

En este artículo exploramos cómo los medios de comunicación colombianos configuran la práctica de la genética humana, reproduciendo ciertos discursos estandarizados sobre ciencia que se encuentran atravesados por el género y la raza. Para este fin llevamos a cabo un análisis etnográfico de la cobertura de la genética humana (poblacional y forense) en dos de los medios de mayor penetración en el país en los periodos de 1992-2006 (periódico) y 2009-2010 (periódico y noticiero). Nuestro argumento es que por una parte, los medios de comunicación presentan a la ciencia genética como única/uniforme/objetiva/neutra/heroica. Por otro lado, presenta sujetos que son simultáneamente marcados y desmarcados en términos de raza, género, clase y geografía. Concluimos que este último mecanismo reproduce y moviliza la idea del mestizaje como una ideología de construcción de nación.
Itinerários terapêuticos: trajetórias entrecruzadas na busca por cuidados
Authors: Pinho Paula Andréa , Pereira Pedro Paulo Gomes
Published: July 2012

A proposta geral deste texto é apresentar os itinerários terapêuticos percorridos por sujeitos soropositivos. Esses percursos, constituídos por inusitadas mesclas e composições, revelam caminhos complexos no enfrentamento do HIV/aids, de pessoas que transitam por terapias numa tentativa de restabelecerem ou preservarem a saúde. Admitindo a existência de numerosas terapias disponíveis, nos empenhamos em analisar os itinerários de terapias por elas denominadas de "tipo religiosa", na sua relação com o modelo biomédico. A etnografia revelou que as interlocutoras não separam a terapia biomédica da religiosa em planos distintos. O que sobressaía era a interação concomitante das duas soluções agenciadas com o mesmo propósito: a saúde. Foi possível observar um continuum terapêutico, ou seja, as opções não se isolam: antes, apresentam-se como partes consecutivas que fluem sem limites claramente delimitados.
Emissões Otoacústicas Evocadas por Estímulo Transiente: protocolos de Triagem Auditiva Neonatal
Authors: Côrtes-Andrade Isabela Freixo , Bento Daniela Veronese , Lewis Doris Ruthi
Published: July 2012

OBJETIVO: descrever os resultados de três protocolos de EOAET de um equipamento automático utilizado em um Programa de TAN. MÉTODO: o equipamento utilizado foi programado com três critérios diferenciados de passa/falha. Protocolo A: Passar em 4 bandas de frequência, não precisando ser consecutivas; Protocolo B: Passar em 3 bandas de frequência, não precisando ser consecutivas e Protocolo C: Passar em 2 bandas de frequência, não precisando ser consecutivas. Os parâmetros para considerar presença de respostas foram: reprodutibilidade acima de 50%, relação sinal ruído > que 3dB em 1.0 e 1.5kHz e > 6dB em 2.0, 3.0 e 4.0kHz. RESULTADOS: 574 orelhas foram analisadas, sendo que as bandas de frequência de 2.0, 3.0 e 4.0kHz foram as que apresentaram percentuais de "passa" mais elevados (94,1; 95,8 e 92,7%, respectivamente). A banda de frequência de 1.0kHz obteve resposta presente em apenas 9,9% das orelhas testadas. Verificou-se que a análise do Protocolo C (2 bandas) foi a que apresentou o maior percentual de passa (96,9%). Porém este percentual não é considerado estatisticamente diferente do Protocolo B, 3 bandas, (96,2%) com valor de p=0,520. Assim, ambas as bandas são consideradas iguais, podendo-se utilizar qualquer uma das duas. Entretanto o Protocolo A (4 bandas) obteve 79,8% de percentual de passa, apresentando uma taxa de falha elevada (22,2%). CONCLUSÕES: deve-se pesquisar, com o padrão-ouro, todos os protocolos para verificação daquele com melhor sensibilidade e especificidade, apesar de terem apresentado resultados similares entre critérios de passa para 2 ou 3 bandas de frequência.
Biodigestão anaeróbia dos dejetos da bovinocultura de corte: influência do período, do genótipo e da dieta
Authors: Orrico Junior Marco Antonio Previdelli , Orrico Ana Carolina Amorim , Lucas Junior Jorge de , Sampaio Alexandre Amstalden Moraes , Fernandes Alexandre Rodrigo Mendes , Oliveira Emanuel Almeida de
Published: July 2012

Objetivou-se com este estudo identificar possíveis alterações na composição e no processo de biodigestão anaeróbia dos dejetos produzidos por bovinos Canchim e Nelore em diferentes períodos do confinamento e alimentados com diferentes proporções de volumoso e concentrado. O experimento foi conduzido em delineamento inteiramente casualizado em esquema fatorial com parcela subdividida no tempo. As parcelas foram compostas por quatro tratamentos: dejetos provenientes de duas dietas (40% de volumoso e 60% de concentrado e 60% de volumoso e 40% de concentrado) e dois genótipos (Canchim e Nelore) e as subparcelas pelos três períodos de colheita dos resíduos (início, meio e final). A eficiência do processo de biodigestão foi avaliada pelas reduções de sólidos totais (ST), sólidos voláteis (SV), número mais provável (NMP) de coliformes totais e termotolerantes, demanda química e bioquímica de oxigênio, além da produção e dos potenciais de produção de biogás e metano. Não houve efeito do genótipo nem do período sobre a composição dos dejetos, no entanto o aumento da proporção de volumoso na dieta levou a menor eficiência do processo, pois foi observado aumento de 26,31% no volume de metano produzido na dieta com 60% de concentrado com relação à dieta com 40%, de concentrado. Também foram observadas importantes reduções no NMP de coliformes totais e termotolerantes ao final do processo, independentemente do tratamento testado.
Síndrome do roubo coronário-subclávio: relato de caso e revisão da literatura
Authors: Miiller Jean Carlo , Candemil Patrick Cardoso , Loures João Marcelo Goncalves da Rocha , Zucco Fabrício Martins , Belz Walmor Erwin , Loures Nilceu Gomes da Rocha , Ortiz Marco Rodrigo , Garcia Rogério Sanchez
Published: July 2012

O fenômeno do roubo coronário-subclávio é definido como o fluxo sanguíneo invertido de uma artéria coronária, por meio de enxerto de artéria mamária interna em direção à subclávia médio-distal, e ocorre devido à estenose significativa ou oclusão total da porção proximal desta última. É uma causa rara, mas significante, de isquemia cardíaca após cirurgia de revascularização miocárdica e pode originar uma síndrome de mesmo nome e com manifestações típicas. Relatou-se o caso de um paciente com esta enfermidade, que foi submetido à angioplastia percutânea com implante de stent. Também revisou-se a literatura a respeito.
Promoção da saúde: a concepção dos profissionais de uma unidade de saúde da família
Authors: Rodrigues Carol Cardoso , Ribeiro Kátia Suely Queiroz Silva
Published: July 2012

Este artigo tem como objetivo analisar as concepções que norteiam as práticas de promoção da saúde dos profissionais de uma unidade de saúde da família em João Pessoa, Paraíba, Brasil. Realizou-se uma pesquisa qualitativa, com técnicas de entrevista e observação participante, tendo como instrumentos a entrevista semiestruturada e o diário de campo. A coleta dos dados ocorreu em abril e maio de 2010. Os informantes-chave foram seis membros da comissão gestora de uma atividade de promoção da saúde e outros dois profissionais, indicados pela comissão, totalizando oito entrevistados. As entrevistas e o diário de campo foram analisados com base no método de análise de discurso. As categorias de análise foram concepções de promoção da saúde, conhecimento da Política Nacional de Promoção da Saúde e ações de promoção da saúde do planejamento à execução. Teve como referencial teórico os documentos das conferências internacionais sobre promoção da saúde e a Política Nacional de Promoção da Saúde. Percebeu-se que os entrevistados tinham um conceito ampliado de saúde, que influencia diretamente a concepção de promoção da saúde; entretanto, há incoerência entre o discurso e a prática. Espera-se que este estudo contribua para uma reflexão das atividades de promoção da saúde desenvolvidas pelos profissionais.
Repercussões do processo de ensinar-aprender em serviços de saúde na qualidade de vida dos usuários
Authors: Delfino Maria Regina Rufino , Karnopp Zuleica Maria Patrício , Rosa Mary Rosane Quirino Polli , Pasin Roseli Ribeiro
Published: July 2012

Estudo de abordagem qualitativa cujo objetivo foi o de conhecer percepções de usuários de serviços de saúde atendidos por docentes e alunos de cursos de graduação em saúde de uma universidade de Santa Catarina, Brasil, sobre a repercussão dessa participação na sua qualidade de vida e saúde. Os dados foram coletados pela técnica da entrevista em profundidade com vinte indivíduos que buscaram atendimento nos locais onde eram realizados os processos de ensino-aprendizagem. O processo de análise-reflexão-síntese dos dados, com base no referencial teórico adotado, evidenciou repercussões positivas na qualidade de vida e saúde dos usuários, particularmente em razão dos atributos identificados nas interações que mediaram o atendimento às necessidades específicas apresentadas por eles. O conjunto de categorias identificado nas interações professor-aluno-usuário pode ser caracterizado como um construto de atenção humanizada em processos de ensino-aprendizagem, o qual por si só, pelos seus atributos de cuidado, representa um espaço terapêutico e de realização para todos os participantes. Processos dessa natureza podem contribuir para a concretização das diretrizes curriculares, integradas às políticas públicas em saúde, as quais orientam para a assistência integral e humanizada, tendo em vista a atenção à saúde para promoção da qualidade de vida da população em diferentes contextos.
Polymerization effects in C-S-H: implications for Portland cement hydration
Authors: Macphee D. E. , Lachowski E. E. , Glasser F. P.
Published: July 2012

Synopsis

29Si NMR has been applied to the study of calcium silicate hydrate (C-S-H) gels. The degree of silicate polymerization in young gels is found to be sensitive to the curing humidity; higher degrees of polymerization are observed for gels cured in drier environments. Compositional effects on polymerization have been investigated and found to be insignificant at CaO/SiO2 ratios greater than about 1·2. At lower lime contents, the predominant silicate species are long chain polymers. The results of the studies on synthetic C-S-H are discussed in relation to the hydration of Ca3SiO5 and historical cement specimens.
Alternative model for the fine porous structure in hydrated tricalcium silicate
Authors: Vollet Dimas R. , Craievich Aldo F.
Published: July 2012

Synopsis

Hydrated tricalcium silicate has been studied by small angle X-ray scattering (SAXS). The experimental SAXS results have been compared with those expected from a lamellar model and from the Debye, Anderson and Brumberger (DAB) model. The theoretical SAXS intensity for the DAB structural model agrees closely with the experimental results. In addition the DAB model provides a good explanation of the different values of specific surface area determined by SAXS, adsorption and proton NMR methods.
The effect of a fracture process zone on a model for crack growth in fibre-reinforced cementitious materials
Authors: Cotterell Brian , Mai Yiu-Wing
Published: July 2012

Synopsis

It is shown that it is comparatively simple to include a fracture process zone in a fictitious crack model for crack growth in fibre-reinforced cementitious materials if it is assumed that the crack faces remain straight. This model can he used to predict the crack-growth resistance curve for a particular specimen geometry and size if the stress-displacement relationship for the material is known. This curve is somewhat different to the curve obtained if the fracture process zone is not modelled. However, if the fracture parameters are obtained from a “master” experimental crack-growth resistance curve, there is little difference between curves obtained with and without modelling the fracture process zone.
Influence of sodium chloride on alkali-silica reaction
Authors: Nixon P. J. , Page C. L. , Canham I. , Bollinghaus R.
Published: July 2012

Synopsis

The possible effect of sodium chloride in increasing the alkalinity of concrete and exacerbating alkali-aggregate reaction has been investigated by experiments involving the addition of sodium chloride and synthetic seawater to cement pastes, mortars and concretes. Measurements of the composition of the pore solution of cement pastes and expansion of mortars and concretes made with reactive aggregates are reported.

It was found that small additions of both sodium chloride and synthetic seawater elevated the hydroxyI ion concentration of the cement pastes to a level similar to that produced by a Portland cement with an equivalent alkali level. Similarly the sodium chloride and synthetic seawater had an effect on the expansion of mortars and concretes which was in line with the effect produced by an equivalent amount of alkali in the cement.
Quantitative characterization of the transition zone in high strength concretes
Authors: Scrivener K. L. , Bentur A. , Pratt P. L.
Published: July 2012

Synopsis

The microstructure of the transition zone in high strength concretes, with and without silica fume, was characterized. Backscattered electron (bse) imaging combined with quantitative image analysis was used to measure the quantity and distribution of unreacted cement, pores larger than 0·5 μm and calcium hydroxide. For concretes of the same water/binder ratio, the silica fume was found to exert only a small influence on the porosity measured in the bulk paste. In the concretes without silica fume the transition zone was more porous than the bulk cement matrix. However, in the concretes with silica fume, the transition zone was much denser, having a level of porosity similar to that of the matrix. These results confirm and support the hypothesis that a major effect of silica fume in concrete is the improvement of the aggregate/matrix bond.
The effect of fine pozzolanic and other particles on the hydration of C3S
Authors: Beedle S. S. , Groves G. W. , Rodger S. A.
Published: July 2012

The effect of a range offine particles on the hydration of C3S has been studied. Graphite and α-alumina particles had no effect and titania only a slight effect, but amorphous silica, clays and γ-alumina had marked effects. Silica produced a strong acceleration of C3S hydration and a reduction in the CH content of the paste. The acceleration of C3S hydration was independent of the surface area of the silica in the range 380–50 m2/g but, in contrast, the removal of CH was markedly accelerated by a reduction in particle size. Clay particles caused less acceleration and had little effect on the CH content of C3S pastes. Particles of γ-alumina in some circumstances produced a marked retardation of C3S hydration. The effects are discussed in terms of the mechanism of C3S hydration.
The binding of chloride ions by pozzolanic product in fly ash cement blends
Authors: Jensen H.-U. , Pratt P. L.
Published: July 2012

The hydration and microstructural development of Portland cement and fly ash blends have been examined when chlorides were present in the mix and in the curing solutions. X-ray diffractometry and thermal analysis were used to identify hydration products and determine pozzolanic activity at various stages of reaction. Changes in microstructure were monitored using electron microscopic techniques. The initial rate of hydration and pozzolanic reaction were accelerated when the mixing water contained chlorides. Chlorides were complexed as chloroaluminate or chloroaluminoferrite hydrates, which formed from reacting C3A, ferrite and calcium aluminate hydrates present in the cement pastes. Additional chlorides may be complexed in fly ash cement blends from calcium aluminate hydrates produced by the pozzolanic reaction.
Nuclear magnetic resonance (NMR) —a powerful tool in cement and concrete research
Authors: Justnes H. , Meland I. , Bjoergum J. O. , Krane J. , Skjetne T.
Published: July 2012

The use of nuclear magnetic resonance (NMR) in cement and concrete research has been reviewed and the potential of the technique for future research has been elucidated. The most important nuclei Jor cement and concrete research are 1H, 13C, 27Al and 29Si, and representative examples are given for each of them. NMR can be utilized to study the degree of hydration, the reactivity of pozzolanic materials, clinker composition, interaction of organic admixtures with cement minerals, the different states of water in concrete, etc.
The chemistry of Portland cement-gasifier slag interactions
Authors: Bland C. H. , Sharp J. H.
Published: July 2012

Gassifier slag (GS) is a potential new cement replacement material which is intermediate in composition between granulated blastfurnace slag (GBFS) and pulverized fuel ash (P FA). Three GSs have been blended with an ordinary Portland cement (OPC) and a sulphate-resisting Portland cement (SRPC) , and comparisons made with a G BFS and a P FA blended with the two cements. Several techniques have been used to investigate the slag-cement interactions in both the early and later stages of hydration. The results indicate that, like GBFS, GS cements show latent hydraulic activity, particularly in the early stages of hydration, while, as with PFA, pozzolanic activity dominates in the later stages.
Microstructure and properties of expansive cement mortar with silica fume
Authors: Bentur A. , Cohen M. D.
Published: July 2012

The effect of adding silica fume to a system of type K expansive cement was studied to characterize the micro-structure, to understand better the influence of the expansive component in mortars with and without silica fume on various physical and mechanical properties. It has heen shown that the expansive component in Portland cement led to coarsening of the porosity of the bulk paste matrix, but caused densening of the microstructure of the transition zone. In the silica fume mortars the influence of the expansive component on the microstructure was not as evident, as the transition zone was dense to start with. These differences in microstructure have been discussed in terms of the physical and mechanical properties of expansive cement mortars with and without silica fume.
Properties of inorganic corrosion inhibition admixtures in steel-containing OPC mortars Part 1: Chemical properties
Authors: Sagoe-Crentsil K. K. , Yilmaz V. T. , Glasser F. P.
Published: July 2012

The chemical interaction between corrosion inhibition admixtures and OPC mortar containing chloride, initially 862 mM/l, has been investigated for three inorganic anions: nitrite, borate and molybdate. After 90 days of cure, the admixture anion solubility in cement pore fluid is variable, ranging from ⪕ 15 mM/l for borate and molybdate, implying precipitation of these ions, to 675 mM/l for nitrite. Chloride ion solubility in cement pore fluid decreases in absolute values but, relative to the control, is somewhat enhanced by addition of admixture anions. However, 90 day corrosion rate measurements indicate that all three admixtures inhibit steel corrosion under conditions of high initial Cl concentrations. The specific chemical modes of corrosion inhihition are discussed.
Research on alkali-activated cementitious systems in China: a review
Authors: Shi Caijun , Wu Xuequan , Tang Mingshu
Published: July 2012

Since the birth of clinkerless alkali-slag cements in the early 1960s, many researchers have been attracted to this field. These materials have great potential because of their low energy cost, good performance and simple production technology. Many cheap, locally available natural resources, industrial products or industrial by-products have been tried as alkaline activators of the potential reactivity of various mineral admixtures. There are three objectives: to produce various clinkerless cements; to improve the performances of blended cements; to use industrial by-products or natural resources to the utmost extent. This Paper summarizes recent achievements in this field in China.
Hydrothermally synthesized aluminium phosphate cements
Authors: Sugama T. , Carciello N.
Published: July 2012

The phase compOSitIOn, exothermal reaction energy, hydrothermal-induced phase transition and development of microstructure in aluminium phosphate cements (APCs), formed by the hydrothermal-catalyzed acid-base reaction between alumina as the base reactant and NH2H2PO4-based fertilizer (Poly-N) as the acid reactant, were investigated. Although the phase compositions of APC depended mainly on the species of alumina and the hydrothermal temperature, the acid-base reaction at 100°C led to the formation of amorphous ammonium aluminium orthophosphate (AmAOP) salt complexes as the major reaction product. The phase transition of AmAOP → crystalline (NH4) 3Al2(PO4)3 and NH4Al(PO4) 2 · OH · 2 · 5H2O occurred at 200°C. Increasing the temperature to 300°C promoted the phase transformations (NH4) 3Al2(PO4)3 → Al2PO4 (OH)3, and NH4Al(PO4)2 · OH · 2 · 5H2O → AlPO4: conversion of non-reactive alumina reactant into γ-AlOOH also occurred. A moderate combination of amorphous and crystalline phases in the cement bodies was responsible for the development of strength. An excessive amorphous → crystal phase transition resulted in a loss in strength, because of the in situ growth of crystalline compounds formed in the amorphous salt matrices, which bind the non-reactive alumina particles into a coherent mass.
The stability of ettringite
Authors: Brown P. W. , Bothe J. V.
Published: July 2012

Ettringite was formed during the hydration of C3A with gypsum at temperatures between 25 and 80°C. Ettringite formation was retarded when hydration was carried out in KOH solutions whose concentrations were as high as 2·0M. Solutions with KOH concentrations between 0·5 and 1 . OM have the greatest retarding effect. In spite of the retarding effect of KOH, ettringite was observed to form at 80°C in 2·OM KOH. Hydration in solutions with KOH concentrations greater than 0·5M also produced syngenite. When C3A is hydrated with gypsum in the presence of C3S, ettringite, C-S-H and CH were formed in the absence of KOH. Hydration of 80% C3S, 10% C3A and 10% gypsum in 0·5M KOH solution was adequate to essentially eliminate the formation of ettringite. Rather, calcium hydroxide and C-S-H containing sulphate and aluminate were formed. Thus the preferred phases when hydration occurs in KOH are C-S-H and CH; whereas the preferred phases for hydration in water are C-S-H, CH and ettringite. Thus, the elimination of ettringite formation by high-temperature curing requires the presence of hydrating C3S. The observations made in studying these model systems are used as the basis for the development of a mechanism of delayed ettringite formation in cement. They are also used in describing a relationship between delayed ettringite formation and the alkali-silica reaction.
The carbonation of OPC and OPC/silica fume hardened cement pastes in air under conditions of fixed humidity
Authors: Richardson I. G. , Groves G. W. , Brough A. R. , Dobson C. M.
Published: July 2012

Slices of hardened pastes of OPC and an OPC/silica fume blend of the same water: solids ratio of 0·5 were carbonated in air for 116 days at a fixed relative humidity. The blended paste slices were found to have carbonated less overall, and to a lesser depth, than the OPC slices. The microstructures of the partially carbonated slices were examined by transmission electron microscopy, and in the case of the OPC the silicate structure was investigated by 29Si NMR.
Properties of polymer-modified mortars made with blended cements
Authors: Banfill P. F. G. , Bellagraa L. , Benaggoun L.
Published: July 2012

This Paper reports an investigation into the properties of polymer-modified mortars made with mixtures of Portland cement and ground granulated blastfurnace slag (GGBFS), microsilica (MS) and pulverized fuel ash (PFA). The polymer latex dispersion used was ethylene vinyl acetate (EVA). Workability, setting time, density, strength, permeability, drying shrinkage and adhesion were all measured, and of the blends tested only those using MS conferred advantages overall. Because of the generally slower development of strength, wet curing is necessary, and this is not satisfactory for EVA.
Freshness of cement: conditions for syngenite CaK2(SO4)2·H2O formation
Authors: Smillie S. , Moulin E. , Glasser F. P.
Published: July 2012

Laboratory experiments disclose that syngenite CaK2 (SO4)2·H2O forms rapidly from mixtures of gypsum and K2S04 only at high relative humidities, ≥96% at 30°C. The concept of a critical humidity below which reaction essentially ceases is developed. The implications of syngenite formation for the freshness of stored cement are discussed: when syngenite is formed from gypsum, water is liberated which may cause prehydration of the cement phases.
Delayed ettringite formation: a microstructural and microanalytical study
Authors: Scrivener K. L. , Taylor H. F. W.
Published: July 2012

Cement pastes were cured at 80°C and examined by scanning electron microscopy, X-ray microanalysis and X-ray diffraction immediately or after storage in water for various periods at 20°C. Ettringite began to form a few days after the heat treatment, as very small crystals thinly dispersed throughout the paste in close admixture with C-S-H. It subsequently recrystallized in cavities typically 5-10μm in size formed by dissolution of clinker grains or in other ways. There were no indications that this latter process disrupted the surrounding material. The results favour the view that the expansion that can be associated with delayed ettringite formation is driven by processes occurring within the paste and not by the formation of ettringite at aggregate interfaces.
Hydration reactions in autoclaved DSP cements
Authors: Sun G. K. , Young J. F.
Published: July 2012

DSP (densified with small particles) cement pastes, made from white Portland cement and silica fume, were autoclaved at temperatures of up to 240°C. The hydration products were characterized using X-ray powder diffraction, 29Si nuclear magnetic resonance spectroscopy and scanning electron microscopy. The influences ofCaO/SiO2 ratio, autoclave temperature and time of reaction were studied. Semi-crystalline calcium silicate hydrate was the major product at low temperatures, with xonotlite, tobermorite, gyrolite, kilchoanite and 8CaO·5SiO2 present at higher temperatures. The nature of the crystalline phase depends on the initial CaO/SiO2 molar ratio; at 240°C, a distinct change in chemistry appears to occur between CaO/SiO2 ratios of 1·3 and 1·1. NMR spectroscopy has proved to be an effective means of studying the polymerization of silicates.
Deformation properties of blended cement concretes containing blastfurnace slag and condensed silica fume
Authors: Alexander M. G.
Published: July 2012

Blended cement concretes incorporating blastfurnace slag and condensed silica fume (CSF) were tested for elastic modulus, creep and shrinkage strains, with a view to comparing their performance with that of plain Portland cement concretes. Exposed and sealed specimens were investigated. The results showed that the exposure condition of the specimens during testing was critical. The addition of slag had the effect of causing a possible small increase in creep and shrinkage at early ages in exposed specimens, but this effect was usually reversed at later ages. Strains were markedly reduced in sealed slag specimens. The addition of CSF effected further moderate reductions in strains. Within-source and between-source variability of Portland cement clinkers with regard to movement properties appeared to be considerable. The use of a blended cement resulted in less variability in cumulative strains.
The influence of silica fume on the fracture properties of paste and microconcrete
Authors: Mindess S. , Qu L. , Alexander M. G.
Published: July 2012

The Paper reports a series of fracture tests on Portland cement pastes and microconcretes with and without silica fume (SF). Water-cement (w/c) ratios of 0·3, 0·5 and O·7 were used. All specimens were tested at 28 days, and 3 day and 7 day tests were also carried out for the 0·3 w/c microconcretes. The fracture tests were based on ISRM Method I, the specimens being chevron-notched cylindrical beams. In comparison with ordinary Portland cement (OPC) materials, the effects of SF were to produce linear pre-peak load-displacement relationships, to strengthen the microconcretes but not the pastes, to embrittle the pastes, to embrittle the low w/c ratio microconcretes (to a small degree), and to toughen the high w/c ratio microconcretes. The observed effects can best be explained in terms of strengthening of the interface bond between paste and aggregate and densifying of the interfacial zone by silica fume.
Long-term hydration of CaSiO4 with combined additions of silica fume, calcium sulpha aluminate and gypsum
Authors: Sun G. , Young J. F. , Matkovic B. , Paljevic M. , Mikoc M.
Published: July 2012

Slow hydration of γ-C2S in mixtures of β and γ polymorphs was observed between 17 and 40 months of curing, but did not occur in the presence of silica fume. The detection of cross-linked silicate species by nuclear magnetic resonance (Q3) is attributed to the formation of silica gel because of the low effective CIS molar ratio in mixtures containing silica fume. The formation of ettringite from additons of C4A3S and gypsum prevents the hydration of β-C2S unless free lime is also present in the mixture.
The hydration of hydraulic active calcium germanates: Part 1. The early hydration of tricalcium germanate
Authors: Trettin R. , Odler I. , Gerdes A. , Oliew G.
Published: July 2012

The initial hydration of Ca3GeO5 was studied using various techniques. Although the structure of tricalcium germanate is isotypic to tricalcium silicate, the hydraulic activity is different. Tricalcium germanate reacts with water very rapidly and an induction period could not be observed. In general, the early hydration of tricalcium germanate has received the same attention that that of tricalcium aluminate has. Also, heat evolution experiments show results similar to those of tricalcium aluminate. In contrast to tricalcium silicate, all the hydration products of tricalcium germanate are crystalline. Concerning the reaction mechanism of tricalcium germanate hydration, the formation of a reaction layer which determines the continuation of the hydration is proposed.
Alkali-activated slag cement and concrete: a review of properties and problems
Authors: Wang Shao-Dong , Pu Xin-Cheng , Scrivener K. L. , Pratt P. L.
Published: July 2012

This paper summarizes the advantageous and disadvantageous properties of alkali-activated slag cement and concrete by reviewing previously published work in English, Russian and Chinese. Practical problems and theoretical questions are discussed. Topics for future work in this field are suggested. The practical problems mentioned are quick setting, the possibility of alkali—aggregate reaction, and the occurrence of efflorescence, shrinkage, microcracks and strength variation. The theoretical questions discussed concerning alkaline activation include the roles of the alkaline anion and cation, the nature of the hydration products, microstructural development and the setting and hardening mechanisms.
Formation of chabazite in mixes of calcium aluminate cement and silica fume used for caesium immobilization
Authors: Fryda H. , Vetter G. , Ollitrault-Fichet R. , Boch P. , Capmas A.
Published: July 2012

The immobilization of caesium with a mix of calcium aluminate cement (CAC) and silica fume (SF) was studied at 50°C. The presence of caesium within the hydration solution leads to the formation of a zeolitic phase of the chabazite family, which immobilizes caesium within the cementitious mix. A severe leach test shows that the immobilization is efficient. Chabazite is also formed when a Cs solution is in contact with an already hydrated CAC-SF mix. The structure of zeolites involves ceramic bonds that are more stable with heat treatment than hydrate bonds, which explains why chabazite is not destroyed by heat treatment at a temperature as high as 750°C. The presence of chabazite is therefore interesting for any application that requires thermal treatment.
Nuclear magnetic resonance study of hydration of synthetic white cement: continuous quantitative monitoring of water and Ca(OH)2 during hydration
Authors: MacTavish J. C. , Miljkovic L. , Peemoeller H. , Corbett J. M. , Jian Jin , Lasic D. D. , Blinc R. , Lahajnar G. , Milia F. , Pintar M. M.
Published: July 2012

The solidification of synthetic white cement is monitored by nuclear magnetic resonance. Proton signals in several different environments are resolved and the time evolution of their dynamics and relative numbers is presented. The amounts of liquid water (the water which has not yet entered the solid structure to become crystalline water) and Ca(OH)2 crystallites are monitored precisely during hydration. The technique gives a quantitative insight into the hydration process as well as the growth (and decay) pattern of various cement paste components.
Statistical modelling of the microfiller effect on the rheology of composite cement pastes
Authors: Nehdi M. , Mindess S. , Aïtcin P-C.
Published: July 2012

Experiments were designed based on a so-called uniform-precision factorial plan to investigate the effect of limestone microfiller replacement of cement on the rheological properties of low w/c ratio super plasticized cement pastes. Cement pastes of different w/b ratios and incorporating various proportions of limestone powder and/or silica fume were assessed in terms of the saturation dosage of super plasticizer using a modified Marsh cone flow time. At a constant flow time, the different cement pastes were further characterized using a coaxial cylinder viscometer, a mini slump test and an induced bleeding test. The flow of mortars corresponding to the various cement pastes were also investigated, and the different rheological tests were compared. The statistical approach used highlighted the micro filler effect on the various rheological characteristics of cement paste, and permitted its modelling over the selected experimental domain.
Modelling of bleeding of cement paste and mortar
Authors: Tan Thiam-Soon , Loh Chang-Kaan , Yong Kwet-Yew , Wee Tiong-Huan
Published: July 2012

Existing bleeding models are unable to explain fully the mechanism of bleeding as the effect of hydration reaction of cement is not considered. To understand the effect of hydration on bleeding, compressibility tests were first conducted for cement paste and mortar at different stages, but all within the first 120 min. Subsequently, bleeding tests were conducted for tall specimens, and, in addition to surface settlement, pore pressure and density profiles were also measured. A rheological model is proposed which can account for the effect of hydration on bleeding. This model is implemented in a self-weight consolidation bleeding model. A number of bleeding tests were conducted and the results were compared with the predictions. The good agreement shows that this model is able to explain the bleeding mechanism of cement paste and mortar, including the effect of hydration, better than previous models.
Well-crystallized and amorphous calcite in concrete slabs exposed to long-term atmospheric carbonation
Authors: Suryavanshi A. K. , Swamy R. N.
Published: July 2012

It is of immense scientific and engineering interest to know the crystalline nature (amorphous and well crystallized) of calcite forming in concrete structural elements subjected to long-term atmospheric carbonation attack. The present study re-examines the crystalline nature of calcite, and also the mechanism controlling its formation in concrete slabs carbonated by exposure to an internal drying environment on a long-term basis. The influence of chloride penetration on the crystalline nature of calcite is also investigated. The crystalline nature of calcite forming in the above slabs was examined at the end of the exposure period at three different locations: at the cast face of the slabs, below the cast face, and immediately below a surface coating used on some of the slabs. Techniques such as differential thermal analysis, X ray diffraction and Volhard's method for the acid-soluble chloride content were used. The results showed that well-crystallized and amorphous calcite form in concrete slabs subjected to a long-term internal drying environment similar to the interior of a building. The concrete close to the cast face of the slabs, on long-term carbonation, showed the presence of a significant proportion of well-crystallized calcite together with well-crystallized vaterite in trace quantities. On the other hand, only amorphous calcite was found to be present on long-term atmospheric carbonation of concrete below the cast face of the slab. In contrast, all the above three carbonate phases, that is, well-crystallized calcite, amorphous calcite together with well-crystallized vaterite, were present in the concrete immediately below the surface coating on exposure to similar conditions. The formation of well-crystallized and amorphous calcite in concrete slabs subjected to long-term carbonation is shown to be related to the flux of atmospheric carbon dioxide through the concrete cover; well-crystallized calcite forms in concrete with a high carbon dioxide flux while amorphous calcite forms in concrete with a restricted carbon dioxide flux. The acid-soluble chlorides present in the concrete cover appear to have no influence on the mechanism leading to the formation of both well-crystallized and amorphous calcite.
AC impedance profiling within cover zone concrete: influence of water and ionic ingress
Authors: McCarter W. J. , Ezirim H.
Published: July 2012

Data are presented on impedance measurements on mature concrete slabs which have been subjected to a cyclic wetting and drying regime, with the test surface of samples exposed to either water or a chloride solution. Both plain ordinary Portland cement concrete and Portland cement partially replaced with pulverized fuel ash and ground granulated blast-furnace slag are studied. The variation of impedance response at discrete points through the cover region (i.e. surface 50 mm) is presented with measurements taken over the frequency range 100 Hz to 10 MHz. Features of the complex response are identified and could be used to study the influence water and ionic ingress into the cover zone concrete.
An AC impedance spectroscopy study of hydrated cement pastes
Authors: Cormack S. L. , Macphee D. E. , Sinclair D. C.
Published: July 2012

In recent years there has been a growing trend to use AC impedance spectroscopy (ACIS) as an in situ and non-destructive method for monitoring changes in the microstructure of cementitious materials. In this paper we discuss experimental results aimed at testing an equivalent circuit model that we have previously developed for interpreting AC impedance data for pore-reduced cement (PRCs). Impedance data for PRC cured in three different humidity environments at room temperature are reported as a function of hydration time. Z* plots show the presence of two semicircular arcs. With time, a decrease in cell conductance is observed, and this is consistent with results of others. However, comparison of data from ‘wet’ and ‘dry’ cured samples show important diflerences in the characteristics of both the low- (LF) and high-frequency (HF) arcs. These differences, and their implications for ACIS measurements on cement systems, are discussed by the use of other immitance formalisms for analysing ACIS data.