Developing Limits for Flowable Concrete

Importance of Sand

The amount of fine aggregate in a mixture can drastically impact the workability. If a mixture has poorly proportioned fine aggregate amounts, the consolidation and surface finishability can be very difficult as shown in the figures below.   If a mixture was too “sandy”, the workability was drastically decrease and the stiffness of the mixture increase.  If the mixture did not have “enough” sand or “too much” rock, the mixture was too “bony” and would not have the plastic flowability and adhesional characteristics needed for the placement and surface finishing for an application.  A YouTube video can be viewed below to understand this behavior. 

Coarse Aggregate

The amount of coarse aggregate in a mixture can also drastically impact the workability.  If a mixture has too “much" coarse or intermediate of a sieve size, the workability was drastically decrease as shown in the figures below.  Also, few YouTube videos can be viewed below to understand this behavior.