"Practically, a sufficient flow range in a premixed paste is a proof of the effective production of FC. When the value of flow seen was lesser than the limit, the mixes of the developed premixed paste and foam was considered in-cohesive. The binders seemed to be covered by air bubbles, which collapsed afterwards. [W]hen the value of flow was greater than the limit, seclusion happened and foam bubbles inclined to collapse."
January 1, 1970
https://en.wikiquote.org/wiki/Foam_concrete