This video iIllustrates good Ready-Mixed Concrete for ICF construction.
Order concrete at a 4" slump and bring it to a 6" slump (as required by codes) at the jobsite. When the concrete truck arrives, climb up and look down into its drum while it is turning at idle speed (NOT mixing speed). If the concrete breaks over the fins in "chunks", it is too dry. SPARINGLY add plasticizer (not water) and have the driver go to mixing speed for 30 to 40 revolutions. Now check again, repeating the process as necessary. At the point where the concrete just begins to "flow" over the fins without cracking, it should be about 6" slump - measure the slump and pour your ICF job.
If your concrete mix isn't right, refuse the truckload (you're paying for usable concrete per your mix design). Pouring unsuitable concrete will cost a lot more when the building has to be torn down and rebuilt.
Not shown are required concrete consolidation (using internal vibration or extensive hand-rodding) nor recommended placement in multiple "lifts" (lift-heights dependent on mix, temperature, consolidation technique, etc).
For details, please refer to experienced professionals, building codes, and our product manual.
Special Thanks to Gary Rhodes for his contribution!