And why is it called “Portland” cement? For more information on the history and technology of concrete, see Robert Courland’s 2011 book Concrete Planet (the link is to my review).
The process of concrete curing is exothermic. It was estimated that if all of the concrete in Hoover Dam had been one continuous pour:
[T]he concrete would have gotten so hot that it would have taken 125 years for the concrete to cool to ambient temperatures. The resulting stresses would have caused the dam to crack and crumble away.
It was not enough to place small quantities of concrete in individual columns. Each form also contained cooling coils of 1" thin-walled steel pipe. When the concrete was first poured, river water was circulated through these pipes. Once the concrete had received a first initial cooling, chilled water from a refrigeration plant on the lower cofferdam was circulated through the coils to finish the cooling. As each block was cooled, the pipes of the cooling coils were cut off and pressure grouted at 300 pounds per square inch by pneumatic grout guns.