Effect of Viscosity modifying agent on flowability of self-compacting mortar

Abstract

This paper presents the results on flowability and viscosity of self-compacting mortar affected by means of powder type viscosity modifying agent (VMA). Higher amount of superplasticizer was necessary for maintaining slump flow by standard cone flow test of mortar in the desire range of 250-270 mm. due to the increase in amount of viscosity modifying agent. Moreover, the viscosity of self-compacting mortar significantly increased with the increase in amount of viscosity modifying agent which could be measured by standard v-funnel test. The measured funnel time gradually increased by increasing amount of viscosity modifying agent. A frictional index (1-R_mb/R_m) representing internal interaction between model coarse aggregate and mortar was employed in order to evaluate flowability and self-compactability of mortar and concrete. The reduction in value of the frictional index meant that internal friction reduced which resulted in the preferable self-compactability of mortar and concrete. Powder type of viscosity modifying agent could be used to increase level of self-compactability of mortar with moderate water to cement ratio (32-35%). The internal friction of mortar increased approximately 14-18% by adding optimum amount of viscosity modifying agent which depended on water to cement ratio. However, this agent was not effective for mortar with low and high water to cement ratio (30% and 40%). The value of index 1-R_mb/R_m slightly increased when the viscosity modifying agent was added. The power type viscosity modifying agent could be considered as a flowability improvement material for self-compacting concrete and mortar. However, it had a limitation that water to cement ratio should be in the range of 32-35%.