I would ask the concrete company to include a slump form with the delivery
truck. The slump form is a tapered conical shaped can-form, pointy end
up, and with no bottom, which you fill
with a sample of the concrete mix, to the top. You place the filled
can on a flat, LEVEL surface, perhaps a smooth scrap piece of Plywood,
then you carefully lift
the conical can STRAIGHT UP, off the concrete sample, and when the wet
concrete mix no longer has the can as a
form, it will "Slump" downward a certain distance from the top level fill
of the can, and this distance in inches, is called the "Slump" of that
concrete. I seem to recall (Soils, concrete class in college) that 4 " of
slump is good, and more than that indicates weaker mix. Less than that
may be O.K., but is more difficult to work with because it is considerably
thicker and chunkier.....As I recall, good strong concrete, when first
mixed wet, will be somewhat chunky and difficult to stir, spread, form,
etc. Most home handymen put WAY, WAY, too much water in it, making it
soupy, and easy to handle, form, spread, etc, but far less strong. You
might be able to buy a slump can at a well stocked, construction oriented
hardware store..They should not be very expensive.....
BTW, after the base is poured, especially if the ground (and weather) is
dry, you should allow the concrete to SLOWLY set. If it dries too
quickly, it will not achieve it's ultimate design strength. Lay a bunch
rags, on top of the base, after an initial "skin" set of the concrete, and
keep them soaked with water, daily.
28 days or so, the concrete will be very close to it's ultimate strength.
Don't load the attachment steel in the concrete for some time after the
pour....I don't know what is safe, but I would not atttach anything for at
least a week or two.
Good luck with your project...
73, DX de Pat, AA6EG/N6IJ
"The Contest Station from the Government"
Marina Amateur Radio Contest Station; N6IJ
599 DX Drive
Marina CA 93933 email@example.com
On Tue, 7 Apr 1998, J.P. Kleinhaus wrote:
> I am scheduled to pour concrete for my (long awaited) tower
> project on Friday. I ordered 5000 PSI mix, but realize that
> short of performing a slump test on site, I have no way of knowing
> if the stuff being delivered will be up to spec.
> Any hints on doing this? Has anyone actually done this before,
> or should I assume that since I ordered 500 PSI, I should end
> up with at least 4000 PSI ? :-)
> 73, J.P. W2XX
> J.P. Kleinhaus, W2XX (fdba AA2DU)
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