Effect of vane configuration on yield stress measurements of cement pastes

Assaad, Joseph J.; Harb, Jacques; Maalouf, Yara

doi:10.1016/j.jnnfm.2016.01.002

Cited by 48 publications

(17 citation statements)

References 16 publications

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“…At slightly higher torque, higher than the critical shearing torque, the angular velocity increases to a constant, elevated value, indicating that the system flows. Studies by Assaad et al [55] indicated that a slotted vane, as used in this study, helped lead to abrupt breakdown of structure. Here, the transitional angular deformation is recorded from Fig.…”

Section: Static Yield Stress: Using Creep Recovery Protocolmentioning

confidence: 77%

Distinguishing dynamic and static yield stress of fresh cement mortars through thixotropy

Qian

Kawashima

2018

Cement and Concrete Composites

197

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The dynamic and static yield stress of fresh cement mortar were measured in a rotational rheometer with a vane geometry using shear rate and shear stress-controlled protocols, respectively. Through a shear rate-controlled steady-state protocol, the equilibrium flow curve is measured and fitted with the Bingham model to obtain dynamic yield stress. A negative slope in the equilibrium flow curve, shear banding and stick-slip phenomena are observed and discussed. Through a stress-controlled creep-recovery protocol, viscosity bifurcation behavior is captured and static yield stress is marked as the creep stress when the bifurcation occurs. Finally, the discrepancy between dynamic and static yield stress is tied to thixotropy.

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Section: Static Yield Stress: Using Creep Recovery Protocolmentioning

confidence: 77%

Distinguishing dynamic and static yield stress of fresh cement mortars through thixotropy

Qian

Kawashima

2018

Cement and Concrete Composites

197

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“…In the preliminary exploration experiment, the test time of each group was determined on the basis of corresponding equilibrium time (Qian and Kawashima, 2016). The initial and stable data of shear stress and corresponding stress relaxation time were recorded upon the completion of the experiment (Assaad et al, 2016). Figure 5 shows the results of the experiment when the concentration of paste was 68% and the cement sand ratio was 1:2.…”

Section: Methodsmentioning

confidence: 99%

Thixotropic behavior of paste

Wu¹,

Yang²

2017

Proceedings of the 20th International Seminar on Paste and Thickened Tailings

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Structure fluid can be broken under shear and rebuilt at the static state because of its thixotropy. The thixotropic behavior of paste slurry in transportation causes a continuous decrease of yield stress and plastic viscosity with time. There is no generally accepted method to measure the thixotropy of paste materials. In this paper, the curve of rheological properties was divided into three parts based on the rheological behavior, and a number of problems were identified using the thixotropy loops measurement to characterize the thixotropy of cement paste. Stress relaxation was considered and the variation of shear stress with time under a constant shear rate was also measured, establishing a yield stress prediction model and plastic viscosity prediction model after considering aspects of paste materials. The total thixotropic time was found to have no relevance to shear rate. Due to paste thixotropy, shear flow area increased and plunger flow area decreased over time and eventually stablized. According to the difficulty level, a standard which divides transportation into different stages was first proposed.

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“…Because of thixotropy, there is more than one state of flocculation for the yield stress measurement: the dynamic yield stress measured through the flow curve at zero shear rate (equilibrium state) and the static yield stress needed to initiate flow before the structure is broken down. The dynamic and the static yield stresses of fresh cement are usually measured in a rotational rheometer with a vane [100,101]. Qian and Kawashima [101] measured the yield stress through shear-rate-controlled and shear-stress-controlled tests.…”

Section: Yield Stress Modelsmentioning

confidence: 99%

A Review of Rheological Modeling of Cement Slurry in Oil Well Applications

et al. 2020

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The rheological behavior of cement slurries is important in trying to prevent and eliminate gas-migration related problems in oil well applications. In this paper, we review the constitutive modeling of cement slurries/pastes. Cement slurries, in general, behave as complex non-linear fluids with the possibility of exhibiting viscoelasticity, thixotropy, yield stress, shear-thinning effects, etc. The shear viscosity and the yield stress are two of the most important rheological characteristics of cement; these have been studied extensively and a review of these studies is provided in this paper. We discuss the importance of changing the concentration of cement particles, water-to-cement ratio, additives/admixtures, shear rate, temperature and pressure, mixing methods, and the thixotropic behavior of cement on the stress tensor. In the concluding remarks, we propose a new constitutive model for cement slurry, considering the basic non-Newtonian nature of the different models.

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Effect of vane configuration on yield stress measurements of cement pastes

Cited by 48 publications

References 16 publications

Distinguishing dynamic and static yield stress of fresh cement mortars through thixotropy

Distinguishing dynamic and static yield stress of fresh cement mortars through thixotropy

Thixotropic behavior of paste

A Review of Rheological Modeling of Cement Slurry in Oil Well Applications

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