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Heading: 1.1Slump of Concrete
I have a doubt about the test method for Slump of Hydraulic-Cement Concrete.

The story is this: In my country we have very coarse sands, the Fineness Modulus usually varies between 3.15 and 3.35. According the ASTM C 33, the F.M. of the Fine Aggregate must be between 2.3 and 3.1, so it's obvious our sands doesn't comply with the Specifications.

This problem causes that we have to increase the Sand Percentage and lower the Gravel Percentage. Usually, the thing goes like this: Sand - 55% vs. Gravel - 45%.

I know the story is kinda long, but my doubt dwells on this situation:

When we perform the Slump Test Method, the concrete's batch doesn't displace, instead of that, the batch collapses. All this, because our aggregates are very coarse (explained above). In conclusion, the center of the cone gets unmeasurable. Unfortunately, we have to take a "point" in the collapsed's batch to measure (with measuring-tape) the slump.


1- Are we doing the slump test right? Taking into account of the conditions.
2-Does this happen in other countries?

Jorge Moquete

The slump test is not a suitable method for harsh concretes. The concrete will shear or collapse when the slump cone id lifted.

Perhaps you should be looking at using the vebe test.


Alan Kirby
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