Stone and paste stop traveling together when concrete free-falls onto rebar, leaves a chute at a bad angle, is mixed too wet, is overvibrated or is pushed sideways with a vibrator. The result is honeycomb and rock pockets in one spot and weak, shrink-prone paste in another. Drop chutes, sensible slump and placing concrete close to its final position keep it in check.
Quit dumping it off the end of the chute from six feet up, you're getting segregation all over that footing.
Also heard as
- separation
Related terms
Honeycomb
Patches of bare, loosely bound stone with open gaps, left where paste never worked in around the coarse rock.
Stinger
An internal concrete vibrator, or specifically the vibrating head on the end of its flexible shaft.
Consolidation
Working fresh concrete, usually by vibration, so it fills the form completely and releases trapped air.
SCC
Self-consolidating concrete, a highly fluid mix that fills forms and wraps rebar under its own weight.