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Proper Stone For Concrete

 
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Old 01-01-2011, 09:08 PM   #1
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Proper Stone For Concrete


I've got a footing to pour in a basement that will be deepened afterwards. This is a older 1900's house, with a 1-2" concrete floor. Underneath the concrete is 12-14" of clean sand, and then another concrete floor of 1-2". Best I can figure is they raised the floor at some point to minimize flooding. Anyway, I've got clean sand, and also clean river rock 3/4-1" size that was used for the perimieter drain.

Can I use this river rock for mixing concrete? I need about 1 yard of concrete, and figure why not use what's there....

Thanks,

Chris
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Old 01-01-2011, 09:23 PM   #2
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Re: Proper Stone For Concrete


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Can I use this river rock for mixing concrete? I need about 1 yard of concrete, and figure why not use what's there....
Don't know why not.

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Old 01-01-2011, 09:29 PM   #3
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Re: Proper Stone For Concrete


The footing in a house takes very little vertical load. The lateral depends on how the wall is attached and it the is first floor than can be a diaphragm that resists a large portion of the load and distributes it.

The basement floor slab if thick enough (usually 3-4") provides the lateral resistance.

Use the 3/4" rock (crushed or rounded makes no difference) and the proper amount of clean sand and cement to make it placeable and you can finish it. For only 1 yard, don't worry about the cost differences unless you are into that world of spending dollars on truck fuel and time to save pennies.

the bottom line is that the slab should be thick enough and you will probably need ready-mix get it in through a window (chute) or have it pumped depending on the access.
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Old 01-01-2011, 09:44 PM   #4
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Re: Proper Stone For Concrete


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Originally Posted by concretemasonry View Post
The footing in a house takes very little vertical load. The lateral depends on how the wall is attached and it the is first floor than can be a diaphragm that resists a large portion of the load and distributes it.

The basement floor slab if thick enough (usually 3-4") provides the lateral resistance.

Use the 3/4" rock (crushed or rounded makes no difference) and the proper amount of clean sand and cement to make it placeable and you can finish it. For only 1 yard, don't worry about the cost differences unless you are into that world of spending dollars on truck fuel and time to save pennies.

the bottom line is that the slab should be thick enough and you will probably need ready-mix get it in through a window (chute) or have it pumped depending on the access.
Yea, like I said.....
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Old 01-01-2011, 09:49 PM   #5
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Re: Proper Stone For Concrete


Great info guys. I will re-use what I've got then.

Thanks,

Chris
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Old 01-01-2011, 10:04 PM   #6
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Re: Proper Stone For Concrete


Is there not a difference in the cohesion properties of rounded river rock vs. a more angular cut limestone for use in concrete? Although, in this particular case it might not matter, it has always been my understanding that the angular properties of mined limestone adds to the compressive strength of the concrete, along with other factors of course.
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Old 01-01-2011, 10:21 PM   #7
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Re: Proper Stone For Concrete


In a test concrete cylinder with uniform prescribed rodding there may be a minor difference. Often, the rounded aggrgates end up being placed better on site since the vibration can be more effective with the same slump.

With our aggregates here, the concrete using crushed limestone is weaker than the rounded igneous rock from the glacial deposits.

A lot has to do with the slump and plasticizers since they can provide the necessary "lubrication" to move the rock around and get good consolidation that is not needed with rounded aggregates. - Just a function of aggregate shape since most rock has more than enough strength.
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Old 02-13-2011, 01:27 PM   #8
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Re: Proper Stone For Concrete


I know you will not find anything written, but it is my experience that river rock just does not bond as well as aggregates such as limestone.
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Old 02-13-2011, 01:30 PM   #9
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Re: Proper Stone For Concrete


Usually in any kind of engineered mix they will spec out for crushed aggregate only due to the better adhesion.
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Old 02-13-2011, 02:34 PM   #10
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Re: Proper Stone For Concrete


I have never had a structural engineer tell me I couldn't use pea gravel in place of crushed limestone. We use this alot on thin slabs and for block fill in reinforced CMU. They are much more concerned about compressive strength which has little to do with the shape of the aggregate. Concrete is weak in tension, whether it has crushed stone or pea gravel, engineers know that and that's what reinforcing steel is for.
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Old 02-13-2011, 03:23 PM   #11
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Re: Proper Stone For Concrete


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I have never had a structural engineer tell me I couldn't use pea gravel in place of crushed limestone. We use this alot on thin slabs and for block fill in reinforced CMU. They are much more concerned about compressive strength which has little to do with the shape of the aggregate. Concrete is weak in tension, whether it has crushed stone or pea gravel, engineers know that and that's what reinforcing steel is for.
The shape of the aggregate does have quite an effect on the compressive strengh. My 6 1/2 sac exposed agg mix will test out stronger than a 6 1/2 sack limestone mix. Besides the river rock being denser, it is also gradated better.
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Old 02-13-2011, 10:07 PM   #12
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Re: Proper Stone For Concrete


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The shape of the aggregate does have quite an effect on the compressive strengh. My 6 1/2 sac exposed agg mix will test out stronger than a 6 1/2 sack limestone mix. Besides the river rock being denser, it is also gradated better.
So the river rock breaks at a higher psi than the crushed limestone? That would be further evidence that the shape of the stone has very little to do with strength.
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Old 02-14-2011, 09:29 PM   #13
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Re: Proper Stone For Concrete


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So the river rock breaks at a higher psi than the crushed limestone? That would be further evidence that the shape of the stone has very little to do with strength.
explain to me, how that is or isn't. Cuz if u can't, I will!
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Old 02-16-2011, 08:12 AM   #14
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Re: Proper Stone For Concrete


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explain to me, how that is or isn't. Cuz if u can't, I will!
O.K. Go ahead Einstein!
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Old 02-16-2011, 04:49 PM   #15
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Re: Proper Stone For Concrete


River rock isn't the desired aggregate for concrete. Can you make good concrete with it, yes. But it is usually used because of material availability. Why truck crushed stone in if river rock is readily available.

What makes river rock less desirable is that it doesn't have as much flexural strength as the crushed limestone. Put two samples that have the same compression strength against eachother, the crushed rock will have better flexural strength.

My father is a concrete construction engineer and said he would rather have a crushed stone for paving due to this.

Just some food for thought.
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Old 02-17-2011, 01:30 AM   #16
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Re: Proper Stone For Concrete


Oh and don't think I am bashing river rock, cause you can make a fine concrete product with it.

I just don't believe it's superior to crushed limestone.
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Old 02-18-2011, 08:22 AM   #17
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Re: Proper Stone For Concrete


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But it is usually used because of material availability. Why truck crushed stone in if river rock is readily available.
Here in Tennessee/Ky we got plenty of both. There will be an upcharge for the river rock though.

We use pea gravel mixes for block fill and thin slabs, cause it fills in small spaces and lays down easier than crushed stone, even 1/2" chips.

And then of course don't forget about exposed aggregate applications. Ever walked barefoot on a crushed limestone exposed aggregate sidewalk?
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Old 02-19-2011, 11:11 AM   #18
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Re: Proper Stone For Concrete


Your right there. But usually when you get chip mix, either pea gravel, or crushed 3/8 rock it's still going to be a premium.

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