Rheology as a tool in concrete science: The use of rheographs and workability boxes

Wallevik, Ólafur H.; Wallevik, Jon Elvar

doi:10.1016/j.cemconres.2011.01.009

Cited by 284 publications

(94 citation statements)

References 12 publications

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“…A primeira proposta de reografia voltada para CAA mostrou as regiões de valores de tensão de escoamento e viscosidade plástica de um CAA ideal [58]. WALLEVIK e WALLEVIK [58] mostraram uma nova proposta de reografia para CAA, na qual consta um gráfico com diferentes áreas coloridas, sendo que cada área representa um tipo de concreto autoadensável em função dos valores de tensão de escoamento e de viscosidade plástica. Nessa proposta, foi apresentado: CAA ("HY-SCC") com alta tensão de escoamento, CAA ("LV-HY-SCC") com baixa viscosidade plástica e alta tensão de escoamento e CAA ("LV-SCC") com baixa viscosidade plástica.…”

Section: Aspectos Relevantes De Autoadensabilidade E De Reologia De Aunclassified

Avaliação dos parâmetros de autoadensabilidade e de reologia do concreto autoadensável

2017

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RESUMOO concreto autoadensável é de complexa obtenção, por isso exige-se um estudo minucioso da mistura e do seu comportamento no estado fresco. De acordo com os requisitos de autoadensabilidade exigidos pela norma brasileira ABNT NBR 15823-1, decidiu-se obter parâmetros de autoadensabilidade e de reologia por meio de estudos em argamassas e, posteriormente, estudos em concretos. Os parâmetros decorrentes da avaliação das argamassas foram obtidos por meio dos seguintes ensaios: mini-slump, mini-funil e caracterização reológica por meio do reômetro da marca Rheotest N4.1. Os parâmetros provenientes da avaliação dos concretos foram obtidos por meio dos ensaios e modelos matemáticos: slump flow, T500, funil V, anel J, caixa L, caixa U, tubo de segregação, parâmetros reológicos estimados por meio de equações matemáticas propostas por Sedran e De Larrard. Com esses parâmetros, foi possível parametrizar ou mapear os concretos autoadensáveis com vistas na norma NBR 15823, bem como foi feita uma avaliação do emprego da classificação dessa norma para o concreto autoadensável. Constatou-se, por exemplo, que o ensaio T500 não apresentou resultados consistentes de viscosidade plástica aparente quando comparados com os resultados do ensaio de Funil V para esta mesma característica. Verificou-se que os ensaios que avaliam habilidade passante, tais como, caixa L e anel J não demonstraram uma boa relação entre seus resultados, assim podendo comprometer a classificação do concreto como autoadensável. Por fim, de maneira geral, observou-se uma importante relação dos parâmetros de autoadensabilidade e de reologia de argamassas e de concretos e, além disso, despertou-se no sentido de melhor avaliar a autoadensabilidade do concreto diante de algumas inconsistências nos resultados de alguns ensaios.Palavras-chave: concreto autoadensável, argamassa, habilidade passante, capacidade passante, resistência à segregação. ABSTRACTThe design of self-compacting concrete is complex, so it requires a thorough study of the mixture and their behavior in the fresh state. According to workability requirements required by the Brazilian standard NBR 15823-1, we decided to get workability parameters and rheology through studies in mortars, and later studies in concrete. The parameters resulting from the evaluation of the mortars were obtained by means of the following tests: mini-slump, mini funnel and rheological characterization using the rheometer of Rheotest N4.1 brand. The parameters resulting from the evaluation of concrete were obtained through the tests and mathematical models: slump flow, T500, V funnel, J ring, L box, U box, segregation tube, rheological parameters estimated by mathematical equations proposed by Sedran and De Larrard. From these parameters, it was possible to parameterize or map the self-compacting concrete according NBR 15823-1, and an assessment was made of the use of this classification standard for self-compacting concrete. It was found, for example, that the T500 test results showed no apparent consistent plastic viscos...

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Section: Aspectos Relevantes De Autoadensabilidade E De Reologia De Aunclassified

Avaliação dos parâmetros de autoadensabilidade e de reologia do concreto autoadensável

2017

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“…For better prediction, although the wet packing conditions of suspension should be evaluated with the influence of chemical admixtures, as per Bentz et al (2012), it is difficult to evaluate the influence of superplasticizers on packing conditions of suspensions. Furthermore, according to Wallevik and Wallevik (2011), superplasticizer is considered to only affect yield stress of cement paste; furthermore, VMA changes the medium of the suspension rather than the particles. Although this theoretical background as per Quiroga and Fowler (2004) and Bentz et al (2012) may not follow a prescribed methodology in a practical aspect, this research agrees with their findings that the addition of chemical admixtures to the samples can be considered a factor causing prediction error.…”

Section: Rheology Of the Mortar Samplesmentioning

confidence: 99%

“…Even though they marginally satisfy the standard of aggregates, its poor quality causes difficulty in mix proportioning (Bairagi et al 1990;Goltermann and Johansen 1997). Also the physical properties of the aggregate affect the performance of concrete and especially dominate workability in its fresh state (Erdogan and Fowler 2005;Westerholm et al 2008;Nanthagopalan and Santhanam 2011;Wallevik and Wallevik 2011;Quiroga and Fowler 2004;Mahmoodzadeh and Chidiac 2013). Therefore, evaluating the aggregate effect on the viscosity of freshly mixed cementitious materials allows us to control and guide the selection of the proper type of aggregates.…”

Section: Introductionmentioning

confidence: 99%

Critical Grain Size of Fine Aggregates in the View of the Rheology of Mortar

Han

Kim

Lee

et al. 2017

Int J Concr Struct Mater

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The aim of this research was to investigate the validity of the Krieger-Dougherty model as a quantitative model to predict the viscosity of mortar depending on various aggregate sizes. The Krieger-Dougherty model reportedly predicted the viscosity of a suspension, which includes cement-based materials. Concrete or mortar incorporates natural resources, such as sand and gravel, referred to as aggregates, which can make up as much as 80% of the mixture by volume. Cement paste is a suspending medium at fresh state and then becomes a binder to link the aggregate after its hydration. Both the viscosity of the suspending medium and the characteristics of the aggregates, therefore, control the viscosity of the cement-based materials. In this research, various sizes and gradations of fine aggregate samples were prepared. Workability and rheological properties were measured using fresh-state mortar samples and incorporating the various-sized fine aggregates. Yield stress and viscosity measurements were obtained by using a rheometer. Based on the packing density of each fine aggregate sample, the viscosity of the mortar was predicted with the Krieger-Dougherty model. In addition, further adjustments were made to determine the water absorption of fine aggregates and was transferred from successful experiment to simulation for more accurate prediction. It was also determined that both yield stress and viscosity increase when the fine aggregate mean size decreases throughout the mix. However, when the mean size of the fine aggregates is bigger than 0.7 mm, the yield stress is not affected by the size of the fine aggregate. Additionally, if aggregate grains get smaller up to 0.3 mm, their water absorption is critical to the rheological behavior.

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“…Changes in the air-void system, namely an increase or decrease in total air content, or a change in air-void distribution can significantly affect the rheological properties of concrete [21][22][23]. Increasing the air content should decrease the viscosity and enhance the effect air has on the yield stress.…”

Section: Changes In Air-void Systemmentioning

confidence: 99%

“…Typically in concrete, increasing the air content would lead to a decrease in plastic viscosity [21][22][23]. In the case of yield stress, the effect depends on the size of the air bubbles [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Changes in rheology of self-consolidating concrete induced by pumping

et al. 2016

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Pumping is an easy and flexible process to place concrete inside a formwork. Many studies have recently been performed to understand and optimize the pumping process and identify the main differences between pumping of conventional vibrated concrete and self-consolidating concrete (SCC). However, due to pumping, changes in fresh concrete properties and the air-void system have been noticed. This paper describes the consequences of pumping on the fresh properties of SCC by means of two experimental pumping campaigns. In many cases, the concrete undergoes a large shear rate in the pipe, thus (re-)dispersing cement particles. This is expected to be the main cause of the observed decrease in plastic viscosity, V-Funnel flow time and pumping pressure resulting from increased flow rate or pumping time.The changes in yield stress or slump flow are anticipated to be influenced by the same phenomenon, but the final outcome is assumed to depend on the availability of residual superplasticizer in the mixing water. Pumping can cause a stable SCC to become segregating if both the yield stress and plastic viscosity decrease, or it can provoke a significant loss in filling ability, passing ability and self-consolidation of the concrete if the yield stress increases dramatically.

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Rheology as a tool in concrete science: The use of rheographs and workability boxes

Cited by 284 publications

References 12 publications

Avaliação dos parâmetros de autoadensabilidade e de reologia do concreto autoadensável

Avaliação dos parâmetros de autoadensabilidade e de reologia do concreto autoadensável

Critical Grain Size of Fine Aggregates in the View of the Rheology of Mortar

Changes in rheology of self-consolidating concrete induced by pumping

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