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| diutan gum |
The viscosity-modifying admixtures (VMAs) contribute to the control of the rheology of grout and are used to enhance plastic viscosity, cohesion, stability, and resis¬tance to bleeding of cement-based systems. This paper reports the results of an investiga¬tion on the effect of VMAs, namely two types of diutan gums and a welan gum, on the rheology behavior of cement grouts. All mixtures were made with two types of superplas¬ticizers. The dosages VMAs were 0.05%, 0.10% and 0.15% with a fixed water-to-cement ratio of 0.40. The investigated fresh properties of the grouts included the mini-slump flow, Marsh cone flow time, plate cohesion, and rheology parameters: namely yield value and the plastic viscosity. Both rheological parameters were obtained using coaxial and vane viscometers. Two control grouts (with and without superplasticizer) were also tested and compared to mixtures containing VMAs. The results indicated that both types of diutan gums were better in controlling the grouts fresh properties and rheology compared to the welan gum.
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