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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.
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