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Posted by Maxwell on October 8, 2007, 11:15 am
Is there a quicker way to judge the flowability of redi-mix concrete than a
slump test?
I have been pouring some of my own concrete with little experience, but it
seems the hardest part is judging what the redi-mix company has sent me.
Seems no mater what slump I order, there is never any consistency in what a
receive, other than it is always much too stiff.
Also, when you have to add water to a truck load of 3 or 4 slump, how long
must the mixer run to insure a uniform mixture of something like a 6 slump?
I am told about 10 gallons per yard will raise (or lower) the slump 1". Is
this good info.
Any and all help appreciated, as well as where to buy a cone or something
for on-site testing.
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Posted by RicodJour on October 8, 2007, 12:50 pm
> Is there a quicker way to judge the flowability of redi-mix concrete than a
> slump test?
>
> I have been pouring some of my own concrete with little experience, but it
> seems the hardest part is judging what the redi-mix company has sent me.
> Seems no mater what slump I order, there is never any consistency in what a
> receive, other than it is always much too stiff.
>
> Also, when you have to add water to a truck load of 3 or 4 slump, how long
> must the mixer run to insure a uniform mixture of something like a 6 slump?
>
> I am told about 10 gallons per yard will raise (or lower) the slump 1". Is
> this good info.
>
> Any and all help appreciated, as well as where to buy a cone or something
> for on-site testing.
Let the concrete company have their driver bring one of their slump
cones.
http://www.bontool.com/product1.asp?P=B12%2D717
R
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Posted by marson on October 8, 2007, 7:45 pm
>
>
>
> > Is there a quicker way to judge the flowability of redi-mix concrete than a
> > slump test?
>
> > I have been pouring some of my own concrete with little experience, but it
> > seems the hardest part is judging what the redi-mix company has sent me.
> > Seems no mater what slump I order, there is never any consistency in what a
> > receive, other than it is always much too stiff.
>
> > Also, when you have to add water to a truck load of 3 or 4 slump, how long
> > must the mixer run to insure a uniform mixture of something like a 6 slump?
>
> > I am told about 10 gallons per yard will raise (or lower) the slump 1". Is
> > this good info.
>
> > Any and all help appreciated, as well as where to buy a cone or something
> > for on-site testing.
>
> Let the concrete company have their driver bring one of their slump
> cones.
>
> http://www.bontool.com/product1.asp?P=B12%2D717
>
> R
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Posted by Bobk207 on October 9, 2007, 1:46 am
> Is there a quicker way to judge the flowability of redi-mix concrete than a
> slump test?
>
> I have been pouring some of my own concrete with little experience, but it
> seems the hardest part is judging what the redi-mix company has sent me.
> Seems no mater what slump I order, there is never any consistency in what a
> receive, other than it is always much too stiff.
>
> Also, when you have to add water to a truck load of 3 or 4 slump, how long
> must the mixer run to insure a uniform mixture of something like a 6 slump?
>
> I am told about 10 gallons per yard will raise (or lower) the slump 1". Is
> this good info.
>
> Any and all help appreciated, as well as where to buy a cone or something
> for on-site testing.
Maxwell-
Take a look at these references...they go a long towards answering
your questions.
http://www.carrollconcrete.com/Images/Others/Images/26p.pdf
http://findarticles.com/p/articles/mi_m0NSX/is_8_51/ai_n16703206
Here is a mix design calculator (but doens't estimate strnghts)
http://www.pensacolatesting.com/dirtknocker/beta.htm
Talk with someone knowledgeable at your concrete supplier, let them
know what you're building.....slab, wall, large foundation, etc.
Have them work with you / give you guidance about a mix design that
meets your project needs; concrete strength, durability, workability,
etc. Agree upon a water / cement (W/C) ratio and withhold some water
at the plant. Have them give you a batch ticket that specifies the
mix maximum W/C ratio & the amount of water in the mix...from this
you'll know how much water you can add to increase slump without
exceeding allowable W/C ratio.
The plant sends it out with minimal water so that the slump can be
adjusted at the jobsite. Unless you have a specific mix design (we
ordered with a mix number that had all the pertinent information
included) you will have batch to batch variation.
Approx 1 gallon per yd will increase slump ~1". Adding 10 gallons
per yard of concrete will make soup since a yd of concrete with a
proper W/C ratio will only have about 30 gallons of water.
After adding water it is only necessary to mix for a few minutes.
A commercial building supply should have slump cones, rods & pans you
can get them online as well.
Oh, considered the use of a vibrator to ease placement & consolidation
of the concrete. A decent sized vibrator can even get low slump
concrete to flow like water......just don't over vibrate!
cheers
Bob
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Posted by DanG on October 9, 2007, 7:34 am
Maxwell,
You do want to keep the water/cement ratio as dry as possible to
maintain strength.
Now that I've said that, let's talk practical. A good 4" slump
concrete will just barely come down the chute, it may actually
need a little help with a shovel unless the chute is very steep.
This is about where you want it, a 5 or 6 is easier to work, but
you are at the threshold of weakening the concrete.
Standing at the back of the truck with the driver trying to guess
at what to add is always that - a guess. Age and experience makes
it a better guess. I gallon for each yard of concrete in the drum
adds about 1 " of slump. If you ordered 3 yards, and it's close,
add 3 gallons. Rev up the truck and try it. You can always add
more, once it is too wet you can't go back. A full truck takes
longer to blend than a short truck.
You do get to where you can tell by the sound of the concrete in
the drum as they pull in. A good driver does this every day, all
day, tell him you want a pretty honest 5 and let him help . Be
aware, they are prone to getting things a bit wet. I suspect
there are lots of non architectural pours that go on where the
finishers get to wet it down to make life easy.
--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
dgriff237@7cox.net
> Is there a quicker way to judge the flowability of redi-mix
> concrete than a slump test?
>
> I have been pouring some of my own concrete with little
> experience, but it seems the hardest part is judging what the
> redi-mix company has sent me. Seems no mater what slump I order,
> there is never any consistency in what a receive, other than it
> is always much too stiff.
>
> Also, when you have to add water to a truck load of 3 or 4
> slump, how long must the mixer run to insure a uniform mixture
> of something like a 6 slump?
>
> I am told about 10 gallons per yard will raise (or lower) the
> slump 1". Is this good info.
>
> Any and all help appreciated, as well as where to buy a cone or
> something for on-site testing.
>
>
>
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