Memorandum from R. L. Murray to C. K. Beck
1 p.


To: C. K. Beck
CC: A. C. Menius

From: R. L. Murray

Visited Knox Concrete Products, Inc., 4918 Kingston Pike, and talked with Mr.
Amos Brown
, plant superintendent. He had been in charge of coleminite block
production for Oak Ridge, working with Mr. S. M. Barnes, was away at the
time of my visit. Their procedure consists of mixing Sweetwater Barytes
3970 (3790 lbs, 100% through 1/2" screen, 90-95% retained on 16 mesh screen)
Coleminite (400 lbs same specifications as ours) and type I cement (830 lbs)
for about 10 minutes in the hopper of the block machine. A much shorter
period, say 2 minutes, would be needed in an ordinary mixer, he states.
Exact amounts of water, to within a pint determined by experience, are
added. If the mix is too dry, the machine cannot handle it; if too wet, it
balls up. For poured structures this may not be as critical. A minimum
of water, however, is used less then 37.5 gal. (straight city water without
special coaling).

The mix is dropped into the machine, vibrated, and pressed at 8000 lbs
with mechanical means. The vibration is supposed to help strengthen the
product, but no such virtue is claimed for the pressure, except to fill
the mold well.

The blocks, of size 4" x 7 5/8" x 11 7/8", weight [~=] 40 lbs, are removed and let dry
somewhat in the kiln. A fine water spray is applied 3 times a day for up
to 3 days, depending on storage facilities. The first large batch, in the
curing stags at the time of my visit, consisted of 7000 blocks. Test blocks
made earlier looked very good. Samples were provided of the mortar only and of the
mortar plus aggregate.

4 x 7 5/8 x 11 7/8 = 364in3 = 5930 cm3
40lb = 40(454) = 18100g
[rho] = 3.05