@article{36983,
abstract = {{AbstractThe use of structured measuring systems to prevent wall slip is a common approach to obtain absolute rheological values. Typically, only the minimum distance between the measuring surfaces is used for further calculation, implying that no flow occurs between the structural elements. But this assumption is misleading, and a gap correction is necessary. To determine the radius correction $$\Delta r$$
Δ
r
for specific geometries, we conducted investigations on three Newtonian fluids (two silicon oils and one suspension considered to be Newtonian in the relevant shear rate range). The results show that $$\Delta r$$
Δ
r
is not only shear- and material-independent, but geometry-dependent, providing a Newtonian flow behaviour in a similar viscosity range. Therefore, a correction value can be determined with only minute deviations in different Newtonian fluids. As the conducted laboratory measurements are very time-consuming and expensive, a CFD-approach with only very small deviations was additionally developed and compared for validation purposes. Therefore, simulation is an effective and resource-efficient alternative to the presented laboratory measurements to determine $$\Delta r$$
Δ
r
for the correction of structured coaxial geometries even for non-Newtonian fluids in the future.}},
author = {{Josch, Sebastian and Jesinghausen, Steffen and Dechert, Christopher and Schmid, Hans-Joachim}},
issn = {{0035-4511}},
journal = {{Rheologica Acta}},
keywords = {{rheology, rheometry, suspension, coaxial, correction}},
publisher = {{Springer Science and Business Media LLC}},
title = {{{Experimental and simulative determination and correction of the effective gap extension in structured coaxial measuring systems}}},
doi = {{10.1007/s00397-023-01383-2}},
year = {{2023}},
}
@article{43034,
abstract = {{Abstract
The accessibility to rheological parameters for concrete is becoming more and more relevant. This is mainly related to the constantly emerging challenges, such as not only the development of high-strength concretes is progressing very fast but also the simulation of the flow behaviour is of high importance. The main problem, however, is that the rheological characterisation of fresh concrete is not possible via commercial rheometers. The so-called concrete rheometers provide valuable relative values for comparing different concretes, but they cannot measure absolute values. Therefore, we developed an adaptive coaxial concrete rheometer (ACCR) that allows the measurement of fresh concrete with particles up to
d
max
=
5.5
mm
{d}_{{\rm{\max }}}=5.5\hspace{.5em}{\rm{mm}}
. The comparison of the ACCR with a commercial rheometer showed very good agreement for selected test materials (Newtonian fluid, shear thinning fluid, suspension, and yield stress fluid), so that self-compacting concrete was subsequently measured. Since these measurements showed a very high reproducibility, the rheological properties of the fresh concrete could be determined with high accuracy. The common flow models (Bingham (B), Herschel–Bulkley, modified Bingham (MB) models) were also tested for their applicability, with the Bingham and the modified Bingham model proving to be the best suitable ones.}},
author = {{Josch, Sebastian and Jesinghausen, Steffen and Schmid, Hans-Joachim}},
issn = {{1617-8106}},
journal = {{Applied Rheology}},
keywords = {{Condensed Matter Physics, General Materials Science}},
number = {{1}},
publisher = {{Walter de Gruyter GmbH}},
title = {{{Development of an adaptive coaxial concrete rheometer and rheological characterisation of fresh concrete}}},
doi = {{10.1515/arh-2022-0140}},
volume = {{33}},
year = {{2023}},
}
@misc{24202,
author = {{Pawelczyk, Sebastian and Jesinghausen, Steffen and Schmid, Hans-Joachim}},
title = {{{Charakterisierung des Fließverhaltens von Frischbeton – Entwicklung eines adaptiven Rheometers (ACCR) und Einfluss von Maßnahmen zur Sedimentationsprävention}}},
year = {{2021}},
}
@article{21948,
abstract = {{Since suspensions (e.g., in food, cement, or cosmetics industries) tend to show wall slip, the application of structured measuring surfaces in rheometers is widespread. Usually, for parallel-plate geometries, the tip-to-tip distance is used for calculation of absolute rheological values, which implies that there is no flow behind this distance. However, several studies show that this is not true. Therefore, the measuring gap needs to be corrected by adding the effective gap extension δ to the prescribed gap height H in order to obtain absolute rheological properties. In this paper, we determine the effective gap extension δ for different structures and fluids (Newtonian, shear thinning, and model suspensions that can be adjusted to the behavior of real fluids) and compare the corrected values to reference data. We observe that for Newtonian fluids a gap- and material-independent correction function can be derived for every measuring system, which is also applicable to suspensions, but not to shear thinning fluids. Since this relation appears to be mainly dependent on the characteristics of flow behaviour, we show that the calibration of structured measuring systems is possible with Newtonian fluids and then can be transferred to suspensions up to a certain particle content.}},
author = {{Pawelczyk, Sebastian and Kniepkamp, Marieluise and Jesinghausen, Steffen and Schmid, Hans-Joachim}},
issn = {{1996-1944}},
journal = {{Materials}},
keywords = {{wall slip prevention, effective gap height, parallel-plate system, structured surfaces, model suspensions, cement paste, fresh concrete}},
title = {{{Absolute Rheological Measurements of Model Suspensions: Influence and Correction of Wall Slip Prevention Measures}}},
doi = {{10.3390/ma13020467}},
year = {{2020}},
}