THE INFLUENCE OF DIFFERENT VISCOSITY-MODIFYING ADMIXTURES ON THE FRESH PROPERTIES OF SUPERPLASTICISED CEMENT-BASED GROUTS

摘要

The viscosity-modifying admixtures (VMAs) are used to enhance the plastic viscosity, the cohesion, the stability, and the bleeding of cement-based systems. This investigation aims to study the effect of VMA, namely two diutan gums and one welan gum, on the rheology behaviour of superplasticised cement grouts. Three dosages of VMAs were used, with fixed water-to-cement ratio of 0.40. Five fresh properties of the grouts were measured: fluidity (mini-slump flow), flowability (Marsh cone flow time), plate cohesion, and rheology parameters: namely the yield value and the plastic viscosity, both obtained using two different viscometers: coaxial and vane. Additionally, the compressive strengths at 1-day, 7-day and 28-day were measured. Two control mixes (with and without superplasticiser) were also tested and compared to mixes containing VMAs. The results indicated that both types of diutan gums were better in controlling the grouts rheology (all fresh state properties) than the welan gum.