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Posted by Duane Bozarth on June 16, 2005, 9:52 am
Rudy wrote:
>
> And if it needs to be 'pumped', I guess the slump is less, right ..so it can
> flow thru the pump easier ?
Slump would then be greater, not less...
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Posted by Robert Allison on June 16, 2005, 10:46 am
Duane Bozarth wrote:
> Rudy wrote:
>
>>And if it needs to be 'pumped', I guess the slump is less, right ..so it can
>>flow thru the pump easier ?
>
>
> Slump would then be greater, not less...
Exactly. And if you are pumping the mix, you have to let the
plant know that in advance. It requires a certain size of
aggregate and a 5-6" slump, which means that the plant has to
adjust the mix so that when it cures, it is at the right PSI.
You can't just order standard 3000PSI mix, then add water to
get it through the pump.
--
Robert Allison
Rimshot, Inc.
Georgetown, TX
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Posted by Matt Whiting on June 30, 2005, 11:07 am
Bob Morrison wrote:
> In a previous post ConcreteFinishing&StuccoGuy says...
>
>>Slab strength and thickness depends on extenuating circs, type of subsoils,
>>frost, use of salt on roads, etc. Reinforcing, if properly applied, greatly
>>improves perform of crete, as does limiting the amount of H2O
>>
>
>
> CF&SG is correct in that rebar and lower water content will improve
> structural performance. However, only the latter will have any effect
> on crack control.
Yes, but rebar will help prevent problems is there is a soft spot in the
ground under the slab that settles a little. It can also prevent cracks
from opening up or shifting vertically.
Matt
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Posted by Bob Morrison on June 30, 2005, 3:38 pm
In a previous post Matt Whiting says...
> > CF&SG is correct in that rebar and lower water content will improve
> > structural performance. However, only the latter will have any effect
> > on crack control.
>
> Yes, but rebar will help prevent problems is there is a soft spot in the
> ground under the slab that settles a little. It can also prevent cracks
> from opening up or shifting vertically.
>
>
Matt:
Quite true. However, I tell the contractors to spend their time and
effort on subgrade preparation. It's easier to do than correctly
placing rebar, and with the current price of steel may even be cheaper.
A good unreinforced slab on properly prepared subgrade with adequate
crack control should not have any problems.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
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Posted by RicodJour on June 30, 2005, 3:57 pm
Bob Morrison wrote:
> In a previous post Matt Whiting says...
> > > CF&SG is correct in that rebar and lower water content will improve
> > > structural performance. However, only the latter will have any effect
> > > on crack control.
> >
> > Yes, but rebar will help prevent problems is there is a soft spot in the
> > ground under the slab that settles a little. It can also prevent cracks
> > from opening up or shifting vertically.
>
> Quite true. However, I tell the contractors to spend their time and
> effort on subgrade preparation. It's easier to do than correctly
> placing rebar, and with the current price of steel may even be cheaper.
>
> A good unreinforced slab on properly prepared subgrade with adequate
> crack control should not have any problems.
NY Code for concrete cover of reinforcing
TABLE 1907.7.1
MINIMUM CONCRETE COVER
MINIMUM
COVER
CONCRETE EXPOSURE inches
1. Concrete cast against and permanently exposed to earth 3
2. Concrete exposed to earth or weather
No. 6 through No. 18 bar 2
No. 5 bar, W31 or D31 wire, and smaller 1-1/2
If I'm reading that right, and you can figure out a way to cast the
driveway above grade and then lower it into place (!), you can go with
as little as a 3" slab. Otherwise you need 6" if it's cast in place
and reinforced.
Weird thing. If you _reinforce_ it, code requires a thicker slab!
Bob's got it right, the slab doesn't move unless something underneath
it does. Preparation - drainage, compaction, etc. - is the key.
R
R
R
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Page 4 of 7 < 1 2 3 > last >>
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