Abstract: The present description is directed to a cement or cementitious mixture that includes fly ash, zinc oxide and borate. Importantly, the cementitious mixture includes greater than 50% of fly ash by weight, or alternatively greater than 75% by weight of fly ash, or still further alternatively greater than 90% or 95% by weight of fly ash. Zinc oxide is incorporated in the cementitious mixture at levels of 2.5% and greater, or alternatively at the amounts of about 5 to 20% zinc oxide. Finally, a borate compound in needed for use as a set retarder.