Influence of Poker Vibration on Aggregate Settlement in Fresh Concrete with Variable Rheological Properties

摘要

Internal vibration is adopted worldwide for consolidating fresh concretes in field construction. Improper manual operation of the vibration process can easily induce segregation and bleeding of fresh concrete and subsequent degradation of long-term durability of real structures. In this paper, the settlement of aggregates in fresh concrete upon vibration was theoretically analyzed and equations were proposed to predict the segregation induced by poker vibration. On the other hand, eight mixtures with variable rheological parameters were subjected to different poker vibrators with two typical vibration durations to prepare prism specimens. The segregation state of each concrete prism was assessed by the apparent density variation along the vertical pouring direction. It was found that segregation caused by poker vibration was much more dominated by plastic viscosity than by yield stress of fresh mortar matrix. Prolonged vibration duration led to a more adverse effect on segregation for the mixture with the relatively lower yield stress, and the high vibration amplitude generally aggravated segregation more severely for the mixture with a higher plastic viscosity.