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► Cite this publication as follows:

Greim M: 22nd Conference and Workshop on Rheology of Building Materials, Appl. Rheol. 23 (2013) 184.Matthias, M. Musialek

The 23rd Stuttgarter Kunststoffkolloquium

Appl. Rheol.23:3 (2013) 183-184 ►

► Cite this publication as follows:

Musialek MM: The 23rd Stuttgarter Kunststoffkolloquium, Appl. Rheol. 23 (2013) 183.

Currently more and more researches have been performing concerning the numerical simulation of the behavior of fresh concrete during pumping or formwork filling. Adequate implementation of the rheology properties of fresh concrete is a determinant key to obtain realistic simulations. However, in many cases, the rheological parameters of the fresh concrete as determined by rheometers are not sufficiently accurate. The common principle of all the rheometers is not to measure directly the rheological parameters of concrete but to measure some basic physical parameters (torque, velocity, pressure, ...) that that in some cases allow the calculation of the rheological parameter in terms of fundamental physical quantities. Errors can be caused by undesired flow phenomena which are not taken into the prediction formulas and by the inaccurate prediction formulas themselves. This is directly related to the poor calibration of the rheometer that cannot cover all ranges of materials. This paper investigates the calibration of the Tattersall MK-II rheometer by performing the numerical simulation for a tremendous range of concrete flowing in the rheometer, using computational fluid dynamics (CFD). This allows to quickly and accurately obtain the rheological properties of fresh concrete, which can then be used consistently for further flow simulations. This method can be applied for all types of rheometer.► Cite this publication as follows:

Le HD, DeSchutter G, Kadri E, Aggoun S, Vierendeels J, Tichko S, Troch P: Computational fluid dynamics calibration of Tattersall MK-II type rheometer for concrete, Appl. Rheol. 23 (2013) 34741.

We discuss the possibility of using penetrometry technique for measuring the yield stress of concentrations made of grains immersed in a colloidal phase, such as concrete or muds. In that aim we used model materials made by suspending glass beads at different concentrations in a kaolin-water paste. We then show that a uniform shear stress develops along the object (plate or cylinder) beyond the entrance length. This shear stress plotted versus the object velocity exhibits a shape similar to the flow curve of the material determined from rheometry. For materials exhibiting the typical flow curve of a simple yield stress fluid, i.e. at bead concentrations smaller than 30 %, the stress associated with an inflection point located at low velocities of this curve appears to correspond to the material yield stress. At larger concentrations of beads the suspensions have a more complex behaviour likely affected by its granular nature at a local scale and the possibility of migration or frictional effects, so that neither conventional rheometry nor penetrometry provide relevant data. We conclude by describing two practical penetrometry techniques for precisely measuring the yield stress of simple pastes.► Cite this publication as follows:

Tikmani M, Boujlel J, Coussot P: Assessment of penetrometry technique for measuring the yield stress of muds and granular pastes, Appl. Rheol. 23 (2013) 34401.

This paper discusses the rheological properties of different contents of a commercially available Southern African clay, Eccabond fine (EBF), modified with hexadecyl trimethyl ammonium bromide, and Cloisite 15A (C15A), modified with dimethyl dehydrogenated tallow quaternary ammonium chloride dispersed in silicone oil. Focused-ion beam scanning electron microscopy shows that both C15A and EBF clays have sheet-like morphologies, but the sheets are more compact in the case of EBF clay. The rheological behavior of different suspensions was characterized by using a rheometer. The EBF suspensions behaved like Bingham fluids and also exhibited higher degrees of viscoelasticity than the C15A suspensions. The Casson model used to calculate the data of the yield stresses for the EBF suspensions was found to fit quite well with the flow curve results. The EBF suspensions obeyed the Schwarzl relation, in which the relaxation modulus (G(t)) illustrated a plateau-like behaviour for EBF suspensions compared to the C15A suspensions.► Cite this publication as follows:

Hato MJ, Pillai SK, Choi HJ, Zhang K: The rheology of non-aquoeous suspension of modified eccabond fine (EBF) clay, Appl. Rheol. 23 (2013) 34870.

The flow of complex fluids is routinely encountered in a variety of industrial manufacturing operations. Some of these operations use rheological methods for process and quality control. In a typical process operation small quantities of the process fluid are intermittently sampled for rheological measurements and the efficiency of the process or the quality of the product is determined based on the outcomes of these measurements. The large number of sample-handling steps involved in this approach cost time and cause inconsistencies that lead to significant variability in the measurements. These complications often make effective process/ quality control using standard rheometric techniques difficult. The effectiveness of control strategies involving rheological measurements can be improved if measurements are made online during processing and sampling-steps are eliminated. Unfortunately, online instruments capable of providing sufficiently detailed rheological characterisation of process fluids have been difficult to develop. Commercially available online instruments typically provide a single measurement of viscosity at a fixed deformation rate. This dependence on a single pre-determined shear rate restricts these instruments from identifying changes in the product or the process, especially if the viscosity at the pre-determined shear rate remains unaltered during these changes. We introduce an Online Rheometer (OLR) that uses small amplitude oscillatory squeeze flow to measure the viscoelastic properties of process fluids in-process and in real time under typical processing conditions. We demonstrate that with an appropriate measuring geometry and amplitude of oscillation, the frequency response of typical non-Newtonian fluids can be accurately measured in a process pipe. We also compare our results with other techniques that are typically used for process rheometry, critically evaluating the utility of the OLR technology for advanced process and quality control.► Cite this publication as follows:

Konigsberg D, Nicholson TM, Halley P, Kealy TJ, Bhattacharjee PK: Online process rheometry using oscillatory squeeze flow, Appl. Rheol. 23 (2013) 35688.

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