Avaliação do comportamento de mistura de argamassas através de reometria rotacional

França, Marylinda Santos de; Cardoso, F. A.; Pileggi, Rafael Giuliano

doi:10.1590/s1678-86212012000200011

Cited by 6 publications

(7 citation statements)

References 11 publications

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“…According to some researchers, the mixing time is one of the factors that influence the paste homogenization. França et al [36,37] have shown in their research that samples with longer mixing times demonstrate more efficiency, producing more fluid and stable mortars.…”

Section: Determination Of the Mixing Procedures For The Production Of mentioning

confidence: 99%

Contribution to the rheological study of cementitious pastes with addition of residues from the processing of ornamental rocks

Sato

Teixeira

2018

Rev. IBRACON Estrut. Mater.

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Brazil is one of the world's largest producers and exporters in the field of ornamental stones. On the other hand, the production and processing of ornamental stones result in a large volume of unused material in the form of sludge, usually discarded inappropriately in sedimentation ponds or landfills. Several researches have been carried out aiming the reuse of this material in cementitious matrixes. In the field of rheology, there are still incipient national studies that use the rheological parameters obtained experimentally to determine the behavior of cement matrix based on Portland cement. Thus, the objective of this work is to characterize rheologically the behavior of cementitious pastes with and without addition of ornamental rock processing residue (RBRO) in its natural condition. Cement pastes were prepared with three a/c ratios (0.45, 0.55, 0.65) and four residue addition contents (0%, 5%, 10%, 15%) and submitted to the flow test. In tests for characterization of the residue, the RBRO presented as a material of specific fineness and mass near the cement, having low reactive activity, indicating that the residue can be used as an inert mineral addition in the cementitious matrix. In the rheological characterization tests of the pulps studied, it was observed in the flow tests that the samples behaved as a non-Newtonian, pseudoplastic and thixotropic fluid.

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Section: Determination Of the Mixing Procedures For The Production Of mentioning

confidence: 99%

Contribution to the rheological study of cementitious pastes with addition of residues from the processing of ornamental rocks

Sato

Teixeira

2018

Rev. IBRACON Estrut. Mater.

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“…No entanto, durante o seu preparo nas obras a mistura com a água deve tornar o conjunto homogêneo e contínuo, resultando em um material que flua sem que ocorra segregação das fases [1][2][3]. Acontece que mesmo com o preciso controle na dosagem das matérias-primas, ainda há considerável variabilidade na etapa de mistura, rápida perda da trabalhabilidade, instabilidade do ar, entre outros fatores, que afetam de forma indesejada o desenvolvimento da microestrutura do material aplicado alterando o seu desempenho em uso [4,5]. A primeira etapa da mistura consiste na adsorção da água na superfície das partículas e ocorre a formação dos aglomerados, devido às forças de interação de van de Waals, forças eletrostáticas entre posições de sítios com cargas opostas e forte interação ou ligação envolvendo as moléculas de água ou hidratos [4].…”

Section: Introductionunclassified

Influência da variação da velocidade de rotação e do tipo de cimento nas propriedades de argamassas de revestimento nos estados fresco e endurecido

Torres¹,

Romano²,

Pileggi³

2017

Cerâmica

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ResumoA etapa de mistura influencia as condições de execução do revestimento de argamassa, visto que desde o primeiro contato dos materiais sólidos com água uma série de eventos de aglomeração e desaglomeração no sistema é verificada. Acontece que durante o processamento das argamassas em obra a utilização de equipamentos com distintos mecanismos de mistura pode modificar o desempenho do sistema de revestimento. Este trabalho foi realizado com o objetivo de avaliar a influência da condição de mistura durante o processamento de argamassas aditivadas com incorporador de ar e formuladas com diferentes tipos de cimento. As misturas foram realizadas em um reômetro rotacional variando-se a velocidade de rotação, porém mantendo-se o tempo total de batimento. Reometria de mistura, ciclo de cisalhamento e teor de ar incorporado foram as propriedades avaliadas no estado fresco, enquanto porosidade, resistência mecânica, módulo de elasticidade e permeabilidade ao ar foram utilizados para avaliação do estado endurecido. Com base nos resultados obtidos pôde-se afirmar que a variação da velocidade de rotação e o tipo de cimento utilizado impactaram as propriedades das composições nos estados fresco e endurecido. Palavras-chave: argamassa, CPIIF, CPIII, energia de mistura, reômetro. Abstract The mixing stage is one of the most important step for the execution of the rendering mortar, since from the first contact of the solid materials with water a series of agglomeration and deagglomeration events in the system is verified. However, during the mortar processing in the buildings the use of different equipments, with distinct mixing concepts, makes this stage very uncontrolled. The main purpose of this work was to evaluate the influence of mixing condition during the processing of mortars with addition of air-entraining agent and formulated with different kind of

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“…This point can be determined in the mixing curve as the moment in which the torque levels start to stabilize and the first derivative of the curve tends to zero asymptotically, Figure 1 [2]. Mixing stages can be assessed by torque vs. time curves, while shear cycles performed immediately after mixing provide information regarding the effects of mixing on the rheological behavior of the material, Figure 1 [9]. In Figure 1, each red point marked on the curve indicates a mixing time when the rheological profile of a mortar was evaluated by a shear cycle (accelerating and decelerating with steps at different rotation speeds).…”

Section: Introductionmentioning

confidence: 99%

“…It can be noted that the shorter the mixing time, the larger the difference between acceleration and deceleration curves (hysteresis), indicating that the system was still rheologically unstable because the mixing was incomplete, therefore the mortar needed an additional energyprovided by the shear cycle -to proceed with dispersion and homogenization and, then, achieve a stable state. For longer mixing times, the hysteresis area gets progressively smaller until it zero or almost zero, which indicates that the procedure provided enough energy for an adequate mixing that produced a rheologically stable mortar for the experimental conditions applied [9]. Fibers are generally incorporated into cementitious materials as reinforcements aiming to improve their strength [10], dynamic properties [11,12], resistance to shrinkage cracking and post-failure residual strength [13].…”

Section: Introductionmentioning

confidence: 99%

Influence of the addition sequence of PVA-fibers and water on mixing and rheological behavior of mortars

França

Cardoso

Pileggi

2016

Rev. IBRACON Estrut. Mater.

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The mixing process of fiber-containing cementitious suspensions is a crucial factor to obtaining a good dispersion of fibers and guarantee adequate mechanical performance of the hardened products. The addition of fibers into the suspension causes reduction of the fluidity of the system due to factors inherent to the fibers, the matrix and their interaction. During mixing, these interactions make dispersion and homogenization processes more difficult due to the formation of fibers - particles agglomerates. Conventional techniques to assess workability of mortars are inadequate to evaluate the rheological behavior of fiber-reinforced systems, in which parameters like viscosity and yield stress are not completely taken into account. Therefore, this work employs rotational rheometry to evaluate the influence of fiber and water addition sequences on mixing and rheological behavior of mortars containing Polyvinyl Alcohol (PVA) fibers. Constant test parameters were: mixing time of 317s; impeller velocity 126.5 rpm; water flow 128g/s. A constant mix design was used with a water content of 16%wt, and a 0.2%vol of fibers were added to the reference composition. Four mixing sequences were studied: S1 and S2 are based on the addition of fibers at different stages of the mixing process; while in S3 and S4 not only the fibers are added at different stages, but also the water addition is performed in two steps (25% first and 75% latter).Results showed that it is possible to optimize the mixing step of fiber-containing systems by changing the moment of fiber addition into the mixture. The introduction of fibers after mixing the dry mortar with water, when it already had achieved its fluidity point, demanded a lower mixing effort and produced a more flowable material.

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Avaliação do comportamento de mistura de argamassas através de reometria rotacional

Cited by 6 publications

References 11 publications

Contribution to the rheological study of cementitious pastes with addition of residues from the processing of ornamental rocks

Contribution to the rheological study of cementitious pastes with addition of residues from the processing of ornamental rocks

Influência da variação da velocidade de rotação e do tipo de cimento nas propriedades de argamassas de revestimento nos estados fresco e endurecido

Influence of the addition sequence of PVA-fibers and water on mixing and rheological behavior of mortars

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