EFFECT OF VISCOSITY MODIFYING AGENTS ON THE RHEOLOGY PROPERTIES OF CEMENT PASTE WITH POLYCARBOXYLATE SUPERPLATICIZER

摘要

Viscosity modifying agents (VMA) can be used to enhance the viscosity of cement paste and avoid layered isolation of paste, so they are often associated with superplasticizer together to improve the stream state of mortar and concrete workability. Polycarboxylate superplasticizers (PC), which have high water reducing and flexible structures, are widely used in grouting materials and self-compacting concrete. However, the effect of different structures of polycarboxylate superplasticizers and viscosity modifying agents on rheological properties of cement paste is still lack of understand. In this paper, the relations of shear rate-shear stress and shear rate-apparent viscosity of cement paste with polycarboxylate superplaticizers and viscosity modifying agents were compared and the basic principle was put forward.The results showed that VMA had significant effect on rheological properties of cement paste. Apparent viscosity and yield value enhanced with the increasing of VMA dosage. The paste with VMA performed pseudoplasticity obviously. The effect of Xanthan Gum on the rbeological properties of the paste was larger than Welan Gum and hydroxyethyl ethers methyl cellulose (HEMC). At high shear rate, the influence of Welan Gum on paste added with ester PC was larger than with ethers PC.