Is it true that the concrete inside used to create the incredible Hoover Dam is still drying to this day, and will be for another 300 or more years?
7 Answers
Steven McQuinn, worked at Hoover Dam
The curing of concrete integrates water molecules into the microscopic structure of the cement binding the concrete, making it much stronger. This process gives off heat.
The concern during the pouring of the concrete for Hoover Dam was that the curing concrete would not cool evenly because of its great volume, and the resulting temperature gradient from a hot interior to cooler edges would cause stress cracks that would weaken the dam. It was important to cool the concrete evenly and to accelerate the cooling.
The solution was to pour the concrete into sectioned forms, and to contain in these forms a network of cooling pipes circulating water cooled evaporatively by a large redwood structure at the dam construction site.
Further forms could not be built and filled until the form beneath was sufficiently cool. The temperature of the circulated cooling water was measured until the federal engineers gave the go-ahead to the construction contractors that a sufficiently cured block was ready to serve as a foundation for pouring concrete into a new form on top of it.
The cooling pipes are still embedded in the concrete, and can be seen protruding from the walls of some deep galleries within the dam. Yes, there are tunnels inside Hoover Dam.
To repeat, concrete doesn’t dry by evaporating the water used to mix it, rather, it cures by incorporating the molecules of the mix water into the crystals of the binding Portland Cement. The curing of Hoover Dam would follow a declining exponential curve that ideally tapers out until the last water molecule is chemically bound to the tricalcium silicate in the Portland Cement binder. (Scientific Principles of Concrete.)
No comments:
Post a Comment