A study was conducted on the effect of a polycarboxylate (PC) admixture on the mechanical, mineralogical, microstructural and rheological behaviour of Portland cement pastes. It was observed that the presence of PC admixture retards the initial cement hydration reactions, although this effect may be offset by possible increased diffusion in later stages. Additionally, the PC admixtures produce a few alterations in the structure and composition of the formed C-S-H gel. The addition of 1% PC admixture in the pastes generates a higher percentage of silicate bridge (Si Q 2 units) mainly at 2 days. The admixture used in this study induced microstructural modifications in the pastes which slightly reduced the porosity; however the admixture did not affect the mechanical strength of the pastes at either 2 or 28 days of hydration. Finally, from the results of the rheological studies it was concluded that a low dosage of PC led to a substantial reduction (over 70%) in the yield stress.

A study was conducted on the effect of a polycarboxylate (PC) admixture on the mechanical, mineralogical, microstructural and rheological behaviour of Portland cement pastes. It was observed that the presence of PC admixture retards the initial cement hydration reactions, although this effect may be offset by possible increased diffusion in later stages. Additionally, the PC admixtures produce a few alterations in the structure and composition of the formed C-S-H gel. The addition of 1% PC admixture in the pastes generates a higher percentage of silicate bridge (Si Q 2 units) mainly at 2 days. The admixture used in this study induced microstructural modifications in the pastes which slightly reduced the porosity; however the admixture did not affect the mechanical strength of the pastes at either 2 or 28 days of hydration. Finally, from the results of the rheological studies it was concluded that a low dosage of PC led to a substantial reduction (over 70%) in the yield stress.

Resumoste trabalho investiga o impacto da utilização de látex poliméricos em propriedades de pastas de cimento Portland branco no estado endurecido. Para tanto, foram utilizados dois látex com propriedades físico-químicas distintas: EVA (etileno de vinil acetato) em pó redispersível, e SAE (estireno acrílico) na forma de emulsão. As pastas foram preparadas com relação água/cimento constante de 0,40, e as quantidades de látex foram variadas, de 5% a 20% de constituintes ativos em relação à massa de cimento. Apesar de os látex poliméricos terem afetado negativamente a reação de hidratação do cimento de forma distinta, houve aumento na resistência mecânica e redução da absorção de água e da permeabilidade ao vapor, com maior teor látex/cimento. Palavras

Santos, Hudson Chagas dos Análise de estruturas de concreto sob o efeito do tempo: uma abordagem consistente com a consideração da viscoelasticidade, da plasticidade, da fissuração, da protensão e de etapas construtivas / H.C. dos Santos.-São Paulo, 2006. 132p. Tese (Doutorado)

The use of waste glass powder (WGP) as a supplementary cementitious material (SCM) rich in pozzolan as a partial replacement for cement has been a viable alternative, from the environmental and economic point of view, to solve problems caused by the high consumption of cement worldwide. Therefore, the objective of this study was to evaluate the effects of the use of WGP, when used as a partial cement substitute, in some properties of cementitious composites (pastes, mortars and concretes), in the fresh and hardened state. Through a systematic literature review, 23 experimental research articles obtained from the world-renowned Science Direct database were analyzed. The results obtained from this review indicate improvements in some properties of cementitious composites with WGP, such as increased compressive strength at advanced ages, increased thermal neutron shielding capacity, reduced penetration of sulfate and chloride ions, mitigation of alkali-silica reaction, reduced thermal conductivity, improved mechanical and chemical properties, including the formation of a new crystalline phase (devitrite) when exposed to high temperatures, reductions in air entrapment, water absorption and porosity. Regarding workability, there was no consensus, however, regardless of the substitution content, all composites were within the slump limits. Therefore, it can be concluded that the use of WGP in cementitious materials produces beneficial effects on some properties of cementitious composites.

RESUMO Este artigo tem como objetivo destacar a influência dos agentes de desforma na qualidade final dos elementos de concreto, frisando as principais consequências e patologias relacionadas ao tipo de desmoldante utilizado, execução da aplicação e limpeza pós desforma. Nesse sentido, busca-se realizar um estudo pautado na revisão integrativa, tendo sido analisadas obras pertinentes ao conteúdo abordado, tomando por base artigos publicados em periódicos e levantamento bibliográfico relevante ao estudo. O banco de dados construído levou em consideração principalmente o relacionamento das obras com o objetivo da pesquisa e utilizou as seguintes fontes de pesquisa: SCIELO, Portal Capes, Google Acadêmico e Science Direct, bem como foram utilizados resultados de dissertações para a construção das discussões da pesquisa. A partir destes, implementou-se uma análise qualitativa das obras e concluiu-se que o uso de maneira errônea dos desmoldantes resulta em uma série de patologias tais como manchas, quebras na seção do elemento de concreto, surgimento de bolhas e/ou vazios na superfície do elemento de concreto, assim como problemas de aderência com revestimentos.

Arquitetura em arcos e soluções de recuperação estrutural: estudo de caso da Igreja Matriz de Nossa Senhora do Amparo, Teresina-PI Arch architecture and structural recovery solutions: a case studyof the Mother Church of Nossa Senhora do

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