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Irina Masalova, Willy Mbasha, Rainer Haldenwang, Alexander Ya. Malkin
Rheokinetics of cement paste hydration during the dormant phase
Appl. Rheol. 28:1 (2018) 15452 (9 pages)
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The hydration kinetics of four CEM I 52.5 N cements in the presence of two different superplasticizers was studied. The kinetics
was characterized by monitoring the evolution of the dynamic modulus at constant frequency on a rotational rheometer. The
method consists of predicting the time dependence of the elastic modulus by a kinetic equation of the self-acceleration type
and fitting the equation to the experimental data. The model defines two main characteristic constants i.e. the characteristic
time which defines the initial rate of hydration and the self-acceleration coefficient. It is shown that the model can accurately
predict the initial hydration of cement paste with and without superplasticizer. The effect of the different cement properties
and their interaction with superplasticizers can be observed in the kinetics of hydration.
► Cite this publication as follows:
Masalova I, Mbasha W, Haldenwang R, Malkin AY: Rheokinetics of cement paste hydration during the dormant phase, Appl. Rheol. 28 (2018) 15452.
R. Elmakki, I. Masalova, R. Haldenwang, A. Malkin, W. Mbasha
Effect of limestone on the cement paste hydration in the presence of polycarboxylate superplasticiser
Appl. Rheol. 26:2 (2016) 25122 (8 pages)
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The addition of certain ingredients in conventional concrete is essential for improving rheological properties of this construction
material. The effect of limestone and superplasticisers on the hydration kinetics of self-compacting concrete (SCC) was
investigated on cement paste scale. These additives interact mostly with cement paste, since aggregates are considered to
be inert materials. The understanding of the effect of these mineral and chemical additives on the hydration kinetics of
cement paste is the key to design a self-compacting concrete with great properties. Four CEM I 52.5 N Portland Cements, limestone
(LS) and one type of superplasticiser (SP) were used in this research. The hydration kinetics were evaluated by monitoring
the storage modulus growth and different coefficients of a self-acceleration kinetics equation were used to depict the
effect of different concentrations of SP with and without the optimum concentration of limestone (30 %) on the hydration
kinetics of cement pastes. It was observed that the rate of hydration increased with the increase in SP concentration depending
on the cement used. The addition of limestone in the superplasticised cement paste significantly retarded the hydration
kinetics for all four cements. The rheological behavior of self-compacting cement paste was found to be very sensitive to the
chemical and physical properties of the cements used.
► Cite this publication as follows:
Elmakki R, Masalova I, Haldenwang R, Malkin A, Mbasha W: Effect of limestone on the cement paste hydration in the presence of polycarboxylate superplasticiser, Appl. Rheol. 26 (2016) 25122.
Willy Mbasha, Irina Masalova, Rainer Haldenwang, Alexander Malkin
The yield stress of cement pastes as obtained by different rheological approaches
Appl. Rheol. 25:5 (2015) 53517 (11 pages)
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Different rheological methods for yield stress estimation of cement pastes during initial hydration were used and results
were compared. These methods include measuring of the hysteresis loop, flow curves (recalculated to the same time of
hydration) and large amplitude oscillating strain (LAOS). Experiments were performed with four Ordinary Portland Cements
from one manufacturer, produced at different factories and one polycarboxylate acid based superplasticiser (SP). The yield
stress values obtained by constructing flow curves is the only method which gives information about the evolution of the
rheological properties, reflecting structure evolution of cements pastes. It was shown that the yield stress values established
by the LAOS method and that calculated from the flow curves are similar while the values found from the downward part of
the hysteresis loops are much lower. Differences in the yield stress values obtained by various methods are related to the different
states of the material corresponding to the kinetics of hydration. The hysteresis loops provide information about
thixotropic characteristics of the material including characteristic times of rebuilding and the rate of yield stress evolution of
cements. The rheological properties are very sensitive to the chemical and physical differences of the cements and could be
used for their characterization.
► Cite this publication as follows:
Mbasha W, Masalova I, Haldenwang R, Malkin A: The yield stress of cement pastes as obtained by different rheological approaches, Appl. Rheol. 25 (2015) 53517.
Nsenda Ngenda Tshilumbu, Irina Masalova
Effect of nanoparticle hydrophobicity on the rheology of highly concentrated emulsions
Appl. Rheol. 23:6 (2013) 62835 (11 pages)
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A series of fumed silica nanoparticles were used as an additional emulsifier for highly concentrated (HC) water-in-oil (W/O)
emulsions. These nanoparticles, with different hydrophobicity index (HI) in the 0.60 - 1.34 and HI > 3 range, were mixed with
the conventional low molecular weight surfactant, sorbitan monooleate (SMO), in the oil phase prior to the emulsification
process. The rheological properties of these emulsions were measured and compared with the properties of emulsions stabilized
with SMO alone. In the mixed emulsifier system, the changes in rheological parameters were clearly expressed as a
function of HI. The mixture of silica nanoparticles and SMO significantly increases the yield stress and plateau modulus of
fresh emulsion, compared to the SMO only system. The effect was found to be more pronounced with a decrease in the HI.
This is probably related to the reduction in micelle content with the decrease in HI, owing to a concomitant increase in the
amount of SMO adsorbed onto the particle surface. Then, interestingly, the Foudazi-Masalova model recently developed for
surfactant-stabilized highly concentrated emulsions (HCE) was found to describe successfully the rheological behavior of
emulsions in the presence of a mixture of surfactant and fumed nanosilica.
► Cite this publication as follows:
Tshilumbu NN, Masalova I: Effect of nanoparticle hydrophobicity on the rheology of highly concentrated emulsions, Appl. Rheol. 23 (2013) 62835.
Reza Foudazi, Irina Masalova, Alexander Malkin
The rheology of binary mixtures of highly concentrated emulsions
Appl. Rheol. 21:2 (2011) 25326 (3 pages)
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The rheological parameters (elastic modules and the yield stress) of binary mixtures of highly concentrated emulsions with
different droplet sizes can be several times lower than additive values in a certain range of concentration. This is related to
the proper packing of small droplets between larger ones without compression of droplets. While the yield stress is practically
absent for these uncompressed droplets, the rather high storage modulus demonstrates the significance of interdroplet
interaction in this system.
► Cite this publication as follows:
Foudazi R, Masalova I, Malkin A: The rheology of binary mixtures of highly concentrated emulsions, Appl. Rheol. 21 (2011) 25326.
Reza Foudazi, Irina Masalova, Alexander Malkin
Effect of interdroplet interaction on elasticity of highly concentrated emulsions
Appl. Rheol. 20:4 (2010) 45096 (10 pages)
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We present a model for osmotic pressure and shear modulus of highly concentrated emulsions by including the interdroplet
interaction in terms of disjoining pressure. The results show that even a small addition in interdroplet interaction can lead to
significant deviations from the classical Princen-Lacasse-Mason models that take into account only the surface energy as the
sole source of elasticity. The newly proposed model predicts new effects, in particular the possibility of nonlinear dependency
of elastic modulus on the droplet size, and can be used to discuss the elasticity sources of highly concentrated emulsions.
In the second part of this article, the unusual elasticity of highly concentrated explosive emulsions is discussed by using the
proposed model.
► Cite this publication as follows:
Foudazi R, Masalova I, Malkin A: Effect of interdroplet interaction on elasticity of highly concentrated emulsions, Appl. Rheol. 20 (2010) 45096.
Irina Masalova, Alexander Ya. Malkin, Reza Foudazi
Yield stress as measured in steady shearing and in oscillations
Appl. Rheol. 18:4 (2008) 44790 (8 pages)
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The yield stresses of five samples (two highly concentrated emulsions, two Kaolin dispersions and mayonnaise)
were determined in two ways. In one case, steady shear experiments were performed over a range of incrementally
decreasing shear rates. The resulting flow curves, plotted as shear stress against shear rate, clearly
showed the existence of a yield stress for each sample, the Herschel-Bulkley model being fitted to obtain values.
In the second case, oscillatory amplitude sweeps were performed at three frequencies, and the .dynamic
yield stress. was defined as the stress at which deviation from linearity occurred; this procedure has often been
used to determine the yield stress of emulsions. It was found that the dynamic yield stress is frequency dependent,
and cannot therefore be thought of as physically meaningful material property. At no frequency did the
dynamic yield stress correlate with the yield stress obtained from the flow curves.
► Cite this publication as follows:
Masalova I, Malkin AY, Foudazi R: Yield stress as measured in steady shearing and in oscillations, Appl. Rheol. 18 (2008) 44790.
Irina Masalova, Alexander Ya. Malkin
Rheology of highly concentrated emulsions - concentration and droplet size dependencies
Appl. Rheol. 17:4 (2007) 42250 (9 pages)
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The concentration and size dependencies of elastic properties of highly concentrated w/o emulsions were studied. The range
of weight concentration of the disperse phase was 90 - 96%, the range of the average droplet size was 16 - 20 μm, and the
droplet size distribution remained unchanged. The disperse phase consists of droplets of over-cooled concentrated aqueous
solutions of inorganic salts. The concentration range being studied lies above the limit of maximal close packing, φ > φm. The
droplet size distribution is fairly wide and the shape of droplets is polygonal.These factors alone determine possible new rheological
effects, such as the elasticity and visco-plastic behaviour of emulsions, as well as the observed form of concentration
and size dependencies of rheological properties of emulsions. The complete flow curves were measured for these fairly new
emulsion systems. It emerged that they were similar to the entire concentration and droplet size ranges being studied. The
concentration dependencies of the yield stress and storage modules corresponded to the Princen-Kiss theory with critical volume
concentration approximately 0.71 - 0.74. However, this theory describes the size dependence of elastic modules incorrectly.
A new model is proposed, which correctly describes the dependencies of elastic modules on both determining parameters
- those of concentration and droplet size.
► Cite this publication as follows:
Masalova I, Malkin AY: Rheology of highly concentrated emulsions - concentration and droplet size dependencies, Appl. Rheol. 17 (2007) 42250.
A.Ya. Malkin, I. Masalova, D. Pavlovski, P. Slatter
Is the Choice of Flow Curve Fitting Equation Crucial for the Estimation of Pumping Characteristics?
Appl. Rheol. 14:2 (2004) 89-95
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The answer to this provocative question is .no.! This is demonstrated by experiment and analysis for two very different materials . a highly concentrated emulsion and an 8%v/v Kaolin clay suspension. The flow curves of both materials clearly showed a low shear Newtonian asymptote and a pseudoplastic domain. The difference in the accuracy of the fitting equations relates mainly to the low shear rate domain. While the Cross equation is adequate over the full flow curve, the power law and the Herschel-Bulkley equations are clearly inadequate for the low shear rate range. These equations as well as the direct numerical method (using the Rabinowitsch- Weissenberg integral) were used for the calculation of the laminar pipe flow transport characteristics and the results were compared with experimental pipe flow data. It was shown that in all cases the maximum error did not exceed 5%, which is quite acceptable for engineering design, indicating that the choice of the flow curve fitting equation was unimportant.
► Cite this publication as follows:
Malkin AY, Masalova I, Pavlovski D, Slatter P: Is the Choice of Flow Curve Fitting Equation Crucial for the Estimation of Pumping Characteristics?, Appl. Rheol. 14 (2004) 89.
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