It's not your grandfather's "5-sack concrete" any more!
WHAT'S NEW IN CONCRETE?
November Program
[On behalf of the rest of the grandfathers and grandmothers in construction who remember specifying concrete strength by number of sacks in the mix, Grandpa George feels compelled to explain what that was all about...]
Before the introduction of ready-mix concrete plants around the time of World War I, all concrete was job-site mixed using mechanical mixers powered by whatever source was available at the time: steam, gasoline, electricity. Before that, concrete was laboriously hand mixed. Regardless of the method, the mix recipe was based on proportion. A standard 94-pound sack of portland cement was one cubic foot. Five-sack concrete was five sacks, or five cubic feet, of cement per cubicyard of concrete. With the addition of the appropriate sand and gravel aggregates and mix water, you ended up with 3,500 p.s.i. concrete. Probably.
Even as ready-mix became more prevalent between the World Wars, became standard because of the World War II, and became dominant thanks to Gen. Eisenhower's Interstates, early in my career some specifiers and most builders still used terms like 3-sack or four-and-a-half-sack to define compressive strength.
Now that I am retired and looking back at construction materials, I am most amazed and excited by the advancements. Our friends at the Concrete Council are going to examine "What's New in Concrete" on 11/12/25 at our November Program and I for one am interested in seeing if, instead of 5,000 psi concrete, we are one on the cusp of 50,000 psi - and how many sacks would that be???????
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George Everding FCSI, CCS, CCCA, AIA, SCIP
Program Committee Chair
Greater Saint Louis Chapter
314-517-7800
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