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CONCRETE SHORT COURSE a most striking experiment with a jar of sand. He
A short concrete course was given by the Col- showed that the addition of five per cent of mois-
lege of Engineering at the Chemistry Building on ture, by weight, fluffs up the volume of the sand
the evening of January 21 and 22. twenty-five per cent. "Bulking" is a considerable
The program of the first night was given in factor in concrete mixing.
three parts. Prof. J. R. Shank of the department The latter part of the first evening was given
of engineering in his talk on "Theories of Propor- over to actual demonstrations and trial concrete
tioning" discussed the following points of inter- mixes to Professor Shank and J. M. Weed of the
est: early ideas, voids, maximum density, the Engineering Experiment Station. Using a water
guide for grading sand and coarse materials, ratio of (1) and adding part sand and part gravel,
and gravel. to make concrete, the proportions were deter-
Professor Shank also discussed the method of mined of each test.
Mr. Edwards of Canada, the consideration of the On the program of the second evening of the
surface factors. The use of fine materials necessi- course were three more discussions. J. M. Weed
tates the use of a greater area of cement than that spoke on "Water-Cement Ratio on the Job." He
of the coarser materials. A greater amount of pointed out that it is highly practical to make sev-
cement must be used with the finer materials. eral trial batches or mixes right on the job and to
Another point that Professor Shank stressed use that one which proves most economical.
was the water-cement ratio; this ratio sums up as J. W. Kelly spoke on "Field Control Methods,"
—so long as the concrete is workable, strength de- giving a full description of the field equipment of
pends upon the amount of water to cement. a concrete inspector.
Fulfilling of specifications, and the arbitrary or Professor Shank discussed "Durable Concrete"
experience proportion was another point of Pro- summing up his talk by formulating a general rule
fessor Shank's discussion. As an example to for mixing concrete. According to Professor
amplify his statements the Professor referred to Shank in mixing concrete "use as large or coarse
the Panama Canal where twice as much cement as a material as conditions will permit; and keep it
other concrete materials was used, which, to a damp in cure as long as conditions will permit."
great degree, assists to preserve this structure. The remainder of the evening was taken up
J. W. Kelly of the Portland Cement Association again by trial tests to determine the yield of a
followed Professor Shank with a talk on the single sack of cement. Moisture, slump and cyl-
"Bulking of Aggregates." Mr. Kelly performed inder tests were made and discussed.
MARCH, 1929