When the Hoover Dam, a marvel of engineering, was constructed between 1931 and 1935, few could imagine the monumental task of not just erecting the world’s tallest dam but ensuring the concrete at its heart would stand the test of time. The dam, an emblem of the American spirit during the Great Depression and a structural behemoth, required an innovative approach to concrete curing that is still ongoing today.
At the core of the dam’s longevity is the curing process of its concrete. Engineers from the era of its construction estimated that it would take around 100 years for the concrete to completely cure. This prolonged period is due to the dam’s colossal size and the heat generated by the curing concrete. If the dam had been constructed in a single pour, “the concrete would have gotten so hot that it would have taken 125 years for the concrete to cool to ambient temperatures.”
To counteract the heat and prevent structural damage, the Hoover Dam was built not as a monolith but in a series of individual trapezoidal columns. These shapes allowed the heat to dissipate more effectively. Moreover, a network of cooling coils, consisting of “582 miles of 1-inch steel pipe,” was embedded within the concrete. The system initially circulated river water before chilled water from a refrigeration plant was introduced to expedite the cooling process.
This refrigeration plant was no small feat, having the capacity to “produce 1,000 tons of ice in 24 hours.” This innovative system reduced the cooling duration to a more practical timeframe, although the curing process continues to this day.
The statistics surrounding the construction of Hoover Dam are staggering. The dam contains “4,360,000 cubic yards of concrete,” and if all materials used were loaded onto a train, “as the engine entered the switch yards in Boulder City, the caboose would just be leaving Kansas City, MO.”
Building the dam during the Great Depression was too costly for a single company to manage independently. Therefore, a consortium of construction companies joined forces under the name Six Companies and successfully secured the project with a bid of $48.8 million. This bid was the largest contract granted by the federal government at that time. Around 21,000 men were employed for the dam’s construction, with an average of 3,500 workers daily. The peak daily workforce exceeded 5,200 laborers in June 1934.
The construction itself was a Herculean task. The “first concrete for the dam was placed on June 6, 1933,” and the “last on May 29, 1935.” On average, “160,000 cubic yards of concrete were placed in the dam per month,” with peak placements reaching “10,462 cubic yards in one day.”
The Hoover Dam not only tamed the Colorado River but also created Lake Mead, the largest reservoir in the United States. While the dam’s primary function was flood control, water diversion, and hydroelectric power generation, it also holds a place in America’s architectural history as a structure that surpassed the Great Pyramid of Giza in its masonry mass. It remains an enduring symbol of innovation and industrial prowess.
Nearly 90 years after its construction, Hoover Dam continues to capture the imagination of visitors and stands as a testimony to human ingenuity. Its ongoing concrete curing process is a lesser-known but vital aspect of its narrative, ensuring that this engineering wonder will remain stable for generations to come.
Relevant articles:
– TIL that the Hoover dam is still curing and will take 15 – 20 years to finally be complete