the present invention relates to pre - blend cement for general - purpose concrete construction containing class - f fly ash , class - c fly ash or slag , and less than about 5 percent of sodium thiocyanate and / or calcium nitrate 2 ), as a substantial replacement for cement . the sodium thiocyanate and / or calcium nitrate are additives for improved high early strength and accelerated setting times , thereby allowing the concrete structure to be put into service sooner , reducing labor cost , and allowing precast concrete and concrete masonry manufacturers to achieve rapid form and mold turnover .