In 1935, the Hoover Dam was completed after pouring approximately 3,250,000 yards of concrete, with an additional 1,110,000 yards used in the power plant and other dam-related structures.
This quantity of concrete would be enough to build 3000 miles of road—a full-sized highway from one end of the United States to the other. Additionally, the dam required about five million barrels of cement, nearly equaling the total quantity of cement utilized by the Bureau in its previous 27 years of existence.
Bear in mind that this was less than 20 years after a standard formula for cement was established.
You might guess, all this concrete posed some challenges. Without engineers’ intervention, it would have taken the massive blocks of poured concrete years to cool, and this gradual drying would have left the pieces susceptible to breaking. To speed up the process, an engineering team designed a mammoth refrigeration machine. The supersized fridge dispensed upwards of a thousand tons of ice every day, speeding up the cooling and lopping decades off the project’s timeline.
Engineers for the Bureau of Reclamation calculated that if the concrete was placed in a single, monolithic pour, the dam would take 125 years to cool, and stresses from the heat produced and the contraction that takes place as concrete cures would cause the structure to crack and crumble. The solution was to pour the dam in a series of blocks that formed columns, with some blocks as large as 50 feet square and 5 feet high. Each 5-foot-tall section has a series of 1-inch pipes installed through which river water and then mechanically chilled water was pumped to carry away the heat. Once the concrete stopped contracting, the pipes were filled with grout. Concrete core samples tested in 1995 showed that the concrete has continued to gain strength and has higher-than-average compressive strength.