Transcript for Hoover Dam Construction, segment 09 of 17

Following the progress of concrete manufacture through its successive stages, we see the several ingredients entering the concrete mixing plant where they were combined scientifically and under rigid inspection into a finished product. With a maximum capacity of twenty-four cubic yards of concrete every three and one-half minutes, the high level mixing plant at Boulder Dam represented the ultimate in plant installations of its kind.

Here, automatic equipment not only controlled the apportionment of the concrete ingredients but in addition maintained a graphic record of every plant operation. From his post on the control deck of the mixing plant, an operator was able to direct the entire mixing cycle, from the initial weighing of the ingredients on through the complete mixing process. The human element was almost completely eliminated as the mechanical equipment was capable of automatically selecting, measuring, weighing, and recording the proper materials in the precise amounts required for the production of a given mix to which the recording dials had previously been adjusted and set.

Here also we find the production line conveyer belt speeding up the process by carrying the component parts from the measuring and weighing hoppers into the batching bins, from which the materials were dumped into the four cubic yard capacity rotary mixers. Water was added in controlled amounts and the entire mass thoroughly agitated as the last step of the economical and efficient manufacture of a concrete strong enough to withstand the enormous pressure to which the dam would be subjected.

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