Jim Stewart wrote:
I just finished a book describing the building
of Boulder Dam, and there's something I don't
understand. The book mentioned that two concrete
batch plants were made, one to product "low-mix"
concrete for the lower portions of the dam and
another to produce "high-mix" concrete for the
top.

The two plants were not run at the same time.
Any ideas as to why they needed two separate
plants and what the difference in the concrete
was?

My speculation:
Modern bath plants vary the cement content in each load in accordance
with the customer's order. The plants used in building that dam didn't
have the technology that we use today to vary cement content so easily,
and since there was plenty of demand (round the clock pouring), it made
sense to have two plants, each producing a diffent mix.

--
Gary Brady
Austin, TX
www.powdercoatoven.4t.com