Concrete MPa

 
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Old 05-02-2012, 02:02 AM   #1
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Concrete MPa


Hi,
When pouring concrete on a commercial job or a residential job, usually the concrete that comes from the concrete plans is mainly a specific Mpa usually 32 Mpa depending on the structure thatís being built. Now if this concrete was to be watered down so that itís easier to work with, will this affect the Mpa of the concrete or would it have that much of an effect on the structure? How much difference would it make if the concrete was watered down on a suspended slab structure? So the question is if concrete was watered down so itís more workable would it have a big effect on the Mpa of the concrete. And would it have more of an effect on a suspended slab?

Frank
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Old 05-02-2012, 05:15 AM   #2
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Re: Concrete MPa


Yes it would

Add 20 gallons and your in trouble...especially on a suspended slab

Order the correct slump from the plant, test it when it arrives, if it's not what you ordered send it back, reject the load.

If its a suspended slab it's been engineered so everything is specified. Including slump

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Old 05-02-2012, 09:06 AM   #3
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Re: Concrete MPa


Can't you find this in your text book?
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Old 05-03-2012, 03:23 PM   #4
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Re: Concrete MPa


These questions seem awful simple.

Quote:
So the question is if concrete was watered down so itís more workable would it have a big effect on the Mpa of the concrete.
Yes.

Quote:
And would it have more of an effect on a suspended slab?
More of an effect in relation to what?
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Old 05-03-2012, 04:36 PM   #5
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Re: Concrete MPa


I give, what is Mpa?

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Old 05-03-2012, 05:09 PM   #6
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Re: Concrete MPa


Megapascal, foreigner's unit of pressure. 1 Mpa equals something like 145 psi.
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Old 05-03-2012, 05:15 PM   #7
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Re: Concrete MPa


Dang foreigners. When ever someone asks me about psi I just put on my most technical looking face and tell 'em, it's up there.

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Old 05-03-2012, 09:05 PM   #8
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Re: Concrete MPa


People in the U.S. are the foreigners and a minority in the world. That is why the U.S has recently dropped to 17th in education (below most of Europe, Japan and obviously far below India and probably even below China).

When I am in a hurry and need to convert to Mpa's, I just call my 8 year old grandson for an accurate answer, but goes to a good public elementary school. He explains that a centimeter is about the same as common mortar joint.
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Last edited by concretemasonry; 05-03-2012 at 09:08 PM.
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Old 05-03-2012, 09:58 PM   #9
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Re: Concrete MPa


You department of highways order their concrete in MPA strength and in meters cubed as well.

If your concrete supplier can't do metric...he's not doing government work
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Old 05-04-2012, 11:42 AM   #10
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Re: Concrete MPa


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You department of highways order their concrete in MPA strength and in meters cubed as well.

If your concrete supplier can't do metric...he's not doing government work
Keep in mind, "some" folks here live in the US, where the Imperial system is still used. Here, government or not, it all works off of PSI...............
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Old 05-04-2012, 02:30 PM   #11
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Re: Concrete MPa


The OP is a student also. Many in academia and the sciences use the metric system
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Old 05-04-2012, 02:37 PM   #12
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Re: Concrete MPa


32mPa=4,641.22 psi
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Old 05-04-2012, 02:52 PM   #13
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Re: Concrete MPa


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The OP is a student also. Many in academia and the sciences use the metric system
I had one teacher in school that used the metric system more than imperial, and that was because he was some alleged concrete genius hailed from Egypt.
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Old 05-04-2012, 03:31 PM   #14
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Re: Concrete MPa


You can fight the metric systen all you want, but the battle was lost decades ago.

The metric system is logical and is based on decimals (10s, 100s, 1000s and since it is based on a firm and identified basis so there is no excuse for errors. The foot-inch, yard system is archaic and is based on the yard (distance from the King's nose to his finger tip extended fully), the inch (distance from one knuckle to another on the same finger) and so on.

Over several decades ago, the land surveyors tossed out the old inch-foot-rod system and went to deecimals to be more accurate and have fewer errors. The metric system is absolute and is no prone to errors in calculation or rounding off square areas. It is also much easier to work with and is more sensible as any youngster can testify.

For old timers like me, there are only a few conversions to remember and they can always sesibly adjusted by a factor of 10, 100, 1000 or so. ASTM material standrards and testing procedures are genrally written showing the metric for information, but more and more are being written in metrics with inch-foot-yard system showning for the uninformed. Almost every auto mechanic knows what metric wrent to use by just looking at the nut.

Contractors have quickly found out that there are fewer errors in layouts and elevations with decimals instead of the old "up a hair" (1/8" or 1/16") that is just a guess.

The student has a better chance of succeeding since he can look at the situation and not have to take chances on conversion factors while others are still trying to convert.

I had a friend (concrete contractor) that had to install about 6 massive foundations with anchor bolts and all the drawings were metric. He realized the problem he was facing and immediately went out and bought metric tapes for everyone after he almost order 10 yards extra of concrete for the first poundation. Once he re-set the bolts, he realized it was the best thing he could have bought because it eliminated errors and made things more accurate.

Indian construction and civil engineers have an advantage because they grew up using both systems.

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Old 05-04-2012, 04:23 PM   #15
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Re: Concrete MPa


I know CalTrans in California uses metric on all their projects!!!

For those who are old school, the easiest method I found when pouring slabs and ordering concrete, every 100 sq.ft. when the slab is 4" thick is so close to 1 m3 you will be fine, i.e. doing an 2000 sq.ft. slab, order 20 m3 you'll be good including the pump. If your doing a commercial plaza and doing 20,000 sq.ft. plus...get a conversion calculator, cause as the quantities rises you could have a truck and half too much based on my loose calculation. By the way, 20,000 sq.ft. @ 4" is 189 m3

Other conversation tricks,

6" wall = sq.ft. X .015
8" wall = sq.ft. x .02
10" wall = sq.ft. x .025
12" wall = sq.ft. x .03

again, they are not accurate, but they are relatively close on smaller residential projects.
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Old 05-04-2012, 05:01 PM   #16
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Re: Concrete MPa


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Originally Posted by concretemasonry View Post


I had a friend (concrete contractor) that had to install about 6 massive foundations with anchor bolts and all the drawings were metric. He realized the problem he was facing and immediately went out and bought metric tapes for everyone after he almost order 10 yards extra of concrete for the first poundation. Once he re-set the bolts, he realized it was the best thing he could have bought because it eliminated errors and made things more accurate.
We do quite a few machine foundations, several over 500 yds. of crete, and many of them come from Italy & Japan. Thus, the blueprints are drawn with metric dimensions. I've tried the metric tapes, but I've found it just as easy personally to just divide by 25.4 to get the inch equivalent. I've actually found the machine drawing style of blueprint more complicated to get a grasp on than the dimensions. We lucked out this spring though, as they actually purchased a WI made gun-drill, with Imperial dimensions that were far easier for me to understand.......

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