However it is laborious and takes time to remove by vibration, and improper or inadequate vibration can lead to undetected problems later.
Additionally some complex forms cannot easily be vibrated.
is a concrete mix which has a low yield stress, high deformability, good segregation resistance (prevents separation of particles in the mix), and moderate viscosity (necessary to ensure uniform suspension of solid particles during transportation, placement (without external compaction), and thereafter until the concrete sets).
In everyday terms, when poured, SCC is an extremely fluid mix with the following distinctive practical features - it flows very easily within and around the formwork, can flow through obstructions and around corners ("passing ability"), is close to self-levelling (although not actually self-levelling), does not require vibration or tamping after pouring, and follows the shape and surface texture of a mold (or form) very closely once set.
This kind of air content (unlike that in aerated concrete) is not desired and weakens the concrete if left.
A sample of freshly mixed concrete is placed in the cone in one lift without tamping or vibration.
The mold is lifted and the concrete allowed to spread.
After spreading ceases, two orthogonal diameters of the concrete patty are measured.
The slump flow is the average of the two diameters.