Over 50 chemical combinations were studied for their effect on the strength gain of mortar when it is below freezing. The chemicals studied were limited to those that are readily available most anywhere, but that are not marketed as admixtures for concrete. Four admixtures were developed from these chemicals that allowed mortar to gain full strength at -10 deg C as rapidly as normal mortar cured at temperatures between 5 and 10 deg C. A host of other chemicals allowed mortar to recover full strength when cooled to the point that cement hydration ceased or that allowed mortar to continually gain modest strength while at low temperature with only minimal loss of ultimate strength. Guidance is provided for expedient field use-for concrete not expected to last more than 5 years.