Cast Earth Retardant

Looking for the retardant used in Cast Earth building.  I want to pour a monolithic form, and need to increase the set time.  I know its proprietary — do you think that a gypsum retarder and cement retarder in conjunction would equal whatever metallurgic retardant that is currently used proprietarily?

Curious about this myself.
Note that the drywall compound that comes as a powder is largely plaster of Paris  and comes in formulas timed to set in anywhere from 5 to 300 minutes.

Here are the percentages from the MSDS.

Plaster of Paris >60
Limestone or Dolomite <10
Expanded Perlite <10
Mica <10
Vinyl Alcohol Polymer <5
Attapulgite <5
Crystalline Silica <5