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N. Ouari, A. Kaci, A. Tahakourt, M. Chaouche
Rheological behaviour of fibre suspensions in non-Newtonian fluids

Appl. Rheol. 21:5 (2011) 54801 (10 pages)

The influence of short fibre addition on the rheological behaviour of different non-Newtonian fluids is investigated experimentally. Two types of suspending fluids are considered: power-law shear thinning fluids and yieldstress shear-thinning fluids. The power-law suspending fluids consist of aqueous xanthan solutions at different concentrations. The yield stress fluids are mortar tile adhesives characterised by different rheological parameters. The flow curves of the suspensions at different fibre contents are determined at controlled stresses. Three rheological parameters are inferred from the flow curves: the yield stress, the consistency and the fluidity index. The influence of the fibres on the rheological behaviour of purely shear-thinning fluids is found to be quite similar to what can be expected for Newtonian suspending fluids. On the other hand, addition of fibres to yield stress granular fluids leads to a qualitatively different change of their rheological properties compared to the case of Newtonian suspending fluids. In particular, it is found that the fibres can lead to the decrease of the apparent viscosity and the yield stress for low fibre concentrations in the case of granular suspending fluids. Our experimental findings indicate that the models for fibre suspensions in Newtonian solvents cannot be used straightforwardly in the case of fibre suspensions in granular materials such as building materials, ceramic materials, etc.

Cite this publication as follows:
Ouari N, Kaci A, Tahakourt A, Chaouche M: Rheological behaviour of fibre suspensions in non-Newtonian fluids, Appl. Rheol. 21 (2011) 54801.

Abdelhak Kaci, Rachid Bouras, Mohend Chaouche, Pierre-Antoine Andreani, Herve Brossas
Adhesive and Rheological Properties of Mortar Joints

Appl. Rheol. 19:5 (2009) 51970 (9 pages)

Adhesive properties of fresh mortar joints containing different dosage rates of a water-soluble polymer (cellulose ether based) are investigated using the probe tack test. This test consists of measuring the evolution of the normal force required to separate at a given velocity two plates between which a thin layer of the sample is sandwiched. Three different adhesive components are inferred from the measured stretching force: cohesion, adhesion and adherence. The influence of the polymer dosage rate and the pulling velocity on the evolution of these adhesive properties is investigated. The adhesive components are then related the rheological properties of the mortars which are shown to behave as Herschel-Bulkley shear-thinning fluids.

Cite this publication as follows:
Kaci A, Bouras R, Chaouche M, Andreani P, Brossas H: Adhesive and Rheological Properties of Mortar Joints, Appl. Rheol. 19 (2009) 51970.

A. Kaci, M. Chaouche, P.-A. Andreani, H. Brossas
Rheological behaviour of render mortars

Appl. Rheol. 19:1 (2009) 13794 (8 pages)

Steady state and transient rheological behaviours of a one-coat render mortar are considered experimentally using a shear rheometer equipped with the vane geometry.The flow curves performed at controlled shear-rates exhibit highly pronounced minima, which is attributed to shear localization and strong thixotropy. This latter property is further investigated separately by considering the temporal growth of the apparent stress at very low shear-rate, reflecting the material's microstructure rebuild up following shearing at different high shear rates. It is found that rebuilding characteristic time is roughly independent upon shear history, indicating that this is a material parameter. The influence of water dosage rate on the rheological behaviour is considered. As expected, apparent viscosity and yield stress decrease with increasing kneading water amount. The rebuilding up kinetics is found to be non sensitive to water dosage rate, suggesting that the material's processability would be preserved when changing this parameter, although significant creeping may be expected at high water dosage rates.

Cite this publication as follows:
Kaci A, Chaouche M, Andreani P-A, Brossas H: Rheological behaviour of render mortars, Appl. Rheol. 19 (2009) 13794.


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