I read how they had to do the staging of concrete pours in order to build Hoover Dam; it's incredible. They actually embedded soft metal pipes in each "block", plumbed them to an on-site refrigeration facility, and ran icy cold water through them so the concret would not get to hot as it set. After each pour had cured, they cut the pipes off flush with the surface and caulked them up.
This complex system of heat mitigation is critical because if the temperature rises too much while the concrete is setting up, it will undergo thermal expansion and solidify in an expanded state. Then, as it cools off, it will contract and form all kinds of cracks and fissures severely weakening the overall structure.
Had they poured Hoover Dam in a single months-long flow of wet concrete, it has been calculated that the core of the dam would have remained wet for over a hundred years.