Rate of thixotropic rebuilding of cement pastes modified with highly purified attapulgite clays

Kawashima, Shiho; Chaouche, Mohend; Corr, David J.; Shah, Surendra P.

doi:10.1016/j.cemconres.2013.05.019

Cited by 131 publications

(44 citation statements)

References 33 publications

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“…8-11 may be misleading due to the y-axis being based on a logarithmic scale). This increase is attributed to increases in the rigidity of the system due to the hydration [33] and other phenomena such as thixotropy [6,34]. Microstructural rebuilding forms a network that contributes to the rigidity of the system [35].…”

Section: Small Angle Oscillatory Shear (Saos)mentioning

confidence: 96%

Effect of mixing method on microstructure and rheology of cement paste

Han

Ferron

2015

Construction and Building Materials

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h i g h l i g h t sInfluence of mixing intensity on rheological behaviors of cement paste was assessed. High mixing intensity can result in increasing the rheological properties. Plasticized pastes were more sensitive to effect of mixing intensity than non-plasticized pastes. Cement pastes prepared using high mixing intensity can be more agglomerated than pastes prepared using low mixing intensity. Effects of the mixing intensity also affected hydration. a b s t r a c tMixing is one of the most important processes for producing concrete. The influence of different mixing methods on the rheological properties and fresh state microstructure of cement pastes were evaluated. In this work, the mixing process of cement paste was based on two different sample preparation methods: ASTM C305 and ASTM C1738. ASTM C1738 uses a high shear mixer, whereas ASTM C305 uses a planetary mixer to homogenize cement paste. A considerable increase in the rheological properties was seen in pastes prepared using the ASTM C1738 protocol versus those prepared according to ASTM C305, especially when a superplasticizer was incorporated. Not only were the rheological properties affected, but differences in hydration kinetics and fresh state microstructure were also observed, with mixtures prepared with ASTM C1738 generally displaying more flocculated microstructural features and accelerated hydration kinetics than mixtures prepared with ASTM C305.

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Section: Small Angle Oscillatory Shear (Saos)mentioning

confidence: 96%

Effect of mixing method on microstructure and rheology of cement paste

Han

Ferron

2015

Construction and Building Materials

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“…Por otro lado, cabe destacarse que en las suspensiones con 0.360% de aditivo reductor de agua de alto rango (HRWRA) y 0.41% de aditivo modificador de la viscosidad (VMA) el rango de incremento de esfuerzo de cizalla se da entre 10 s -1 y 40 s -1 , atribuyéndole esta estabilidad a el efecto espesante que confiere el aditivo VMA. En todos los casos se puede observar que el efecto tixotrópico influye en las suspensiones cambiando su viscosidad en el tiempo, y una velocidad de cizallamiento no es suficiente para destruir la microestructura por completo (Kawashima, Chaouche, Corr, & Shah, 2013) (Mostafa & Yahia, 2017 Figura 1 a) Curvas de flujo de la suspension con relación agua/cemento 0.25 cambiando la concentración de HRWRA desde 0.04%, 0.120% y 0.360% y con adición de 0.41% de VMA. b) 0.34 c) 0.40 d) 0.46…”

Section: Comportamiento Reológicounclassified

Propiedades De Flujo en Materiales Cementantes: Tixotropía De Suspensiones De Cemento Portland Blanco

Ojeda-Farías¹,

Mendoza-Rangel²,

Hébraud³

et al. 2019

Memorias Conpat 2019

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The knowledge of flow properties on cementitious materials in fresh state is of vital importance for an adequate quality control during its applications. In the new era of the concrete digitalization the thixotropy of cementitious materials should be taken into account especially in self levelling and 3D printing applications, due to the benefits of the change of viscosity over time. The aim of present work is to characterize the development of thixotropy on white Portland cement suspensions studying its physical and chemical contributions. A rheological approach has been used to study pastes with water to cement ratios of 0.25, 0.34, 0.40 and 0.46 furthermore the use of high range water reducing admixture in concentrations of 0.04%, 0.120% and 0.360%, and a viscosity modifying admixture with 0.41% of concentration. Results show that by measurements of viscosity over time is possible uncouple the physical and chemical thixotropies, and by an empirical model the physical contribution that is exponential with time was identifying, followed by linear growth that is ascribed to the hydration reactions of suspensions.

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“…Metakaolin clay addition in cementhas been found to stabilize pastes, especially at prolonged mixing or higher w/b ratio [32]. And nanoclays have been shown to increase yield stress [33], apparent viscosity [34] and cohesiveness [35] of cement paste at modest dosages. Based on the results of the references studies it can be expected that nanoclays can slow particle migration, which supports that  2 corresponds to the granular phase.…”

Section: A Modified Thixotropy Model For Mortarmentioning

confidence: 99%

Flow onset of fresh mortars in rheometers: Contribution of paste deflocculation and sand particle migration

Qian

Kawashima

2016

Cement and Concrete Research

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Shear-inducedparticle migration is widely recognized to be a challenge in characterizing the rheological properties of fresh cement-based mortars. In this study, we aim to quantify shearinduced particlemigration by characterizing the stress decay process during constant shear flow with the aid of a modified thixotropy/migration model. It is found that a conventionally used single exponential model is not sufficient to fit the stress decay and describe the destructuration and sand migrationof mortar under shear. Instead, a two exponential model is needed to capture the interaction of sand particles and the suspending cement paste phase.Model parameters are used to quantify the effect of sand volume fraction, clay addition, and applied shear rate on thekinetics and intensity of colloidal deflocculation and sand migration. Results provide evidence that the colloidal and granular contributions to the overall stress decay of mortars can be represented by each of the two exponentials.

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Rate of thixotropic rebuilding of cement pastes modified with highly purified attapulgite clays

Cited by 131 publications

References 33 publications

Effect of mixing method on microstructure and rheology of cement paste

Effect of mixing method on microstructure and rheology of cement paste

Propiedades De Flujo en Materiales Cementantes: Tixotropía De Suspensiones De Cemento Portland Blanco

Flow onset of fresh mortars in rheometers: Contribution of paste deflocculation and sand particle migration

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