A dry mix of a calcined oxide of Ca and/or Mg and an acid phosphate and fly ash with or without insulating extenders useful in permafrost conditions. Calcined oxide is present at about 12% to about 40% by weight and the acid phosphate is present at about 35% to about 45% by weight. The fly ash is present at about 10% to about 50% by weight with the fly ash being between about 50% to about 100% class F with the remainder class C. Insulating extenders are present in the range from 0% to about 15% by weight of the combined calcined oxide and acid phosphate and fly ash. 0.1% to about 0.5% boric acid and/or borate by weight of the dry mix is present.
 The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the U.S. Department of Energy and The University of Chicago representing Argonne National Laboratory.