Rheology superplasticizers

The cement composition affects the rheological behavior of the system cement pastes having low C3S/ C2S and C3A/C4AF ratios have a higher viscosity when the superplasticizer addition is delayed [27],... 

Compatibility with other admixtures (such as WRAs and superplasticizers) so that rheology of the mix is not significantly altered, set is not drastically extended, or heavy air-entrainment and foaming is not produced. 

Furthermore two types of polycarboxylate ether superplasticizer (PCE) with varying charge density of the backbone were chosen for the investigations. The backbone charge determines the adsorption velocity of superplasticizers on clinker phases and early hydration products and thus influences the time dependent rheological performance as well as the setting. Table 1 provides a detailed overview of the used admixtures. 

In the presented paper the influence of varied environmental temperatures on the effect of two types of stabilising agent in combination with superplasticizer on rheology and setting is demonstrated. With regard to the influence of temperature on the performance of SCC the following items can be... 

The selection and addition time of superplasticizer to a concrete mixture should be based on the experimental verification performed on the mixture composed of the same components that will be used in HPC production. However, it can be presumed in advance that the carboxylate ether based superplasticizer will provide the best rheological properties. The properties of superplasticizers were discussed in Sect. 6.6. 

In a superplasticized cement a suitable suUbnated naphthalene-based superplasticizer is interground with the binder (Rosetti et al, 1992 Bouzoubaa et al, 1998). Under these conditions the rheological properties of the produced concrete are more uniform than in cases in which the superplasticizer is added to the concrete mix in the course of mixing. The added superplasticizer also acts as a grinding aid. 

It is common to add to the fresh mix appropriate amoimts of a superplasticizer, by which measiue the negative effect of microsihca on rheology may be largely or completely eliminated As well as reducing the amount of water boimd to the surface of the microsilica particles, the superplasticizer also causes an effective dispersion of these partieles within the concrete mix. Under such conditions the individual particles of microsilica can occupy spaces between the coarser cement grains that would otherwise be filled with water. This may result in a reduction of the amoimt of water needed to fill the empty spaces between cement particles, and in the formation of a denser matrix with a... 

Banfill, P.F.G., and Gill, S.M. (1993) Superplasticizers for ciment fondu effect on rheological properties of fresh paste and mortar. Advances in Cement Research 5,131-138. 

A superplasticizer has to be added, to disperse the fine microsihca particles and to improve the rheology of the fresh concrete mix. Sirlfonated naphthalene or melamine based products have been foimd to be well sirited for this pirrpose (Cheong et al,... 

The replacement of a part of Portland cement by fly ash or crushed limestone flour improves the rheology of concrete mix and allows reduction of the amount of superplasticizers necessary to obtain the required workability. 

Kucharska, L., Moczko, M. (1993) Influence of cement chemical composition on its response to superplasticizer addition in the light of the rheological research, in Proc. Interuniv. Sem. Tech, The Netherlands University of Eindhoven pp. 135 3. 

Figure 10 shows the effect of a SMF-based superplasticizer on a cement paste. Large irregular agglomerates of cement particles predominate in a water suspension (Fig. 10a). The addition of a superplasticizer causes dispersion into small particles (Fig. 10b). A viscometer is used to measure the effect of a superplasticizer on rheology. Figure 11 plots the viscosity changes in cement containing SNF exposed to different times.

Nawa, T., Eguchi, H., and Fukuya, Y., Effect of Alkali Sulfate on the Rheological Behavior of Cement Paste Containing Superplasticizer, Am. 

Superplasticizing admixtures are used widely in high performance concrete production. Not only do they influence the rheological parameters, but also the setting characteristics. These effects depend on the type and dosage of the admixture. In Fig. 17, the role ofthree types of superplasticizers, viz., 0.5% Ca-SNF, commercial SMF, or Na-SNF on the hydration of slag cements is examined. Addition of the superplasticizer results in the retardation in terms of the time of appearance of the exothermal peak and also a decrease of the peak intensity. Na-SNF retards most of the superplasticizers studied. 

Palacios, M., P. Bowen, M. Kappl, M. Stuei C. Pecharroman, U. Aschauer and F. Puertas (2012). Repulsion Forces of Superplasticizers on Ground Granulated Blast Furnace Slag in Alkaline Media, from AFM Measurements to Rheological Properties . Materiales de Construccion 62 (308) 489-513. 

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