ST-70 — PARTS & OPERATION MANUAL — REV. #4 (05/29/07) — PAGE 17
ST-70 — CONCRETE MIX INFORMATION
The sand content of pumpable concrete is very important. It is
one of the two major ingredients that change due to regional
location (the other is the rock or gravel).
Above is a typical sieve analysis of washed concrete sand
(W.C.S.) to A.S.T.M. C33 specifications.
The total of the “Accumulated % Retained” is the Fineness
Modulus (F.M.). The ideal F.M. is between 2.50 and 2.75, but the
correct F.M. does not guarantee pumpability. Besides having a
correct F.M. the percentage of sand by weight that passes through
the No. 50 sieve must be between 15 and 30 and through the
No. 100 sieve 5 and 10. The total of #50 and 100 mesh particles
must be between 25 and 35 percent.
This fine material plus the cement will provide the necessary
film of lubrication to move the concrete inside the delivery system.
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