I Have Talked To A Friend That Used Straight Portland To Do The Same He Said It Worked Well You Will Have To Let It Sit For About 24hrs Or So. If It Is Humid In Your Area Dont Do It Because Well You Know What Happens With Cement And Water.
Sodium metasilicate or Tri Sodium Phosphate. I have used both, and they work great. But i am curious if folks out there use them in there mix together, separate or do you prefer one over the other.