An 18″ concrete wingwall is place for a flood control system. The air temperature is 38 degree F. According to “Design and Control of Concrete Mixtures, the concrete for the wingwall should be what minimum temperature?

An 18″ concrete wingwall is place for a flood control system. The air temperature is 38 degree F. According to “Design and Control of Concrete Mixtures, the concrete for the wingwall should be what minimum temperature?