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Unregistered
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Posts:2321
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| 01/03/2002 10:58 AM |
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what is to prevent ribar from popping out with icf 50 yr later as it does on bridges etc? i see chunks as large as 4 " deep! |
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LARRY
Registered Users
Posts:123
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| 01/03/2002 12:54 PM |
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quote:
what is to prevent ribar from popping out with icf 50 yr later as it does on bridges etc? i see chunks as large as 4 " deep!
What is ribar?
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OKBlocker
Registered Users
Posts:635
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| 01/03/2002 1:36 PM |
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Marke,
What you see happening on bridges and overpasses is called spalling, a result of the freeze/thaw cycle that occurs in the winter months. Another factor that causes this breakdown is the salt and chemicals applied to the surface to thaw the ice.
However, I have seen stress cracks and spalling due to age and heavy vibration of bridge structures and colums.
These conditions should never have reason to occur in any ICF residential structure.
Understand? Hope this helps. |
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IConForm
Registered Users
Posts:22
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| 01/03/2002 10:19 PM |
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Some admixtures in the concrete also increase internal corrosion of the rebar, as does the rebar's distance from the surface of the concrete (as you mention, 4"). Also, doesn't the initial corrosion condition of the rebar have an effect? (I'm a newbie, just surmising!) Also, the concrete used in large structures is different than that which is used in (relatively) thin walls and slabs. Regular concrete would overheat as the hydration of setting occurrs in a large mass.
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Unregistered
Registered Users
Posts:2321
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| 01/04/2002 4:45 PM |
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quote:
quote:
what is to prevent ribar from popping out with icf 50 yr later as it does on bridges etc? i see chunks as large as 4 " deep!
What is ribar?
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Unregistered
Registered Users
Posts:2321
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| 01/04/2002 4:47 PM |
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thanks
but freeze thaw will happen here in wisconsin to icf's also, will it not?
thanks!
What you see happening on bridges and overpasses is called spalling, a result of the freeze/thaw cycle that occurs in the winter months. Another factor that causes this breakdown is the salt and chemicals applied to the surface to thaw the ice.
However, I have seen stress cracks and spalling due to age and heavy vibration of bridge structures and colums.
These conditions should never have reason to occur in any ICF residential structure.
Understand? Hope this helps.
[/quote] |
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Unregistered
Registered Users
Posts:2321
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| 01/04/2002 4:47 PM |
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thanks
but freeze thaw will happen here in wisconsin to icf's also, will it not?
thanks!
What you see happening on bridges and overpasses is called spalling, a result of the freeze/thaw cycle that occurs in the winter months. Another factor that causes this breakdown is the salt and chemicals applied to the surface to thaw the ice.
However, I have seen stress cracks and spalling due to age and heavy vibration of bridge structures and colums.
These conditions should never have reason to occur in any ICF residential structure.
Understand? Hope this helps.
[/quote] |
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Unregistered
Registered Users
Posts:2321
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| 01/04/2002 5:14 PM |
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[quote]
[quote]
what is to prevent ribar from popping out with icf 50 yr later as it does on bridges etc? i see chunks as large as 4 " deep!
What is ribar?
ribar is re-inforcing steel bars put inside the concrete to strengthen it |
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OKBlocker
Registered Users
Posts:635
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| 01/04/2002 6:14 PM |
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IConForm,
Some chloride based accelerators will cause corrosion of rebar. Certainly the initial condition will set the stage for the "life" of the rebar if corrosion takes place. Non-chloride accelerators are quite often used when the possibility of corrosive penetration of deicing salts, for example, can be expected. The relevance of distance to surface is simply the relative probability that "penetrants" that are corrosive may get in contact with the steel. Something 4" away from the surface is less likely to corrode than something 2", for example.
Regarding large concrete masses, many times these structures will use a "cooler" cement so that hydration temperatures do not reach excessive levels that would be detrimental to the strength progressions of the concrete. ASTM C-150 provides for classifications of cement and a Type IV cement has specific properties to limit the "heat of hydration" to those levels that are acceptable for large mass placement such as dams, vaults, etc. ORMCA
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OKBlocker
Registered Users
Posts:635
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| 01/04/2002 6:25 PM |
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UNREGISTERED:
"but freeze thaw will happen here in wisconsin to icf's also, will it not?"
It is my opinion that the interior heat of the house would be sufficient to keep the temperature of the concrete from cycling above and below freezing to such a degree that would cause damage.
Also, you need water to penetrate the concrete and then freeze, thus causing the spalling.
My Oklahoma winters aren't that severe!
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seflpolyst
Registered Users
Posts:147
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| 01/05/2002 8:49 AM |
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one of the most important reasons why rebar spalling is not likely to happen with icf's is the exterior protective layer of eps. it not only keeps the structure from going through the teperature cycles that an exposed structure may endure, but it also keeps the corrosives away from penetrating the concrete.
case in point: on a 30 year old polysteel 5 story condo in daytona, smack on the ocean, the steel in the slab balconies is starting to spall, a typical problem with many older concrete structures near the beach. the walls are spotless, free from cracking or spalling. on the balconies people apply exterior carpeting, which holds the salt from the air, or do not maintain, ie paint the slabs, and the salt is able to seep into the concrete.
peter juen
s/e florida polysteel inc. |
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markross
Registered Users
Posts:1035
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| 01/05/2002 11:03 PM |
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selfpolyst:
I was wondering who was going to be able to answer this one for this lad. Good one.
Mark Ross
"Le Canuck" |
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jdcoombs
Registered Users
Posts:57
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| 01/07/2002 9:57 AM |
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Let's summarize what most of the replies have pointed. Rebar does not "pop out" on its own. It will cause spalling of the concrete under conditions of corrosion. This obviously is a problem in certain applications, but it only occurs in the constant or persistent exposure to water and (usually) some corrosive chemical (calcium chloride, deicers, etc) AND when those are allowed to make it to the reinforcing steel. For above-grade walls where the steel is in the center of the wall, this almost never occurs. But when corrosion is a concern, like beach houses, retaining walls, etc.; steps can be taken to reduce the likelihood of it happening. ACI code guidelines are meant to address just that. Higher strength (4000 psi) concrete, minimizing the use of accellerants, use of pozzolans (fly-ash, etc.) and smaller, closer spaced rebar all help to reduce corrosion. But as stated, it's really not much of a concern for the next 300 years, let alone 50.
With 4" pieces of concrete popping out it is more likely ASR (alkaline silica reactivity) that is the culprit. We'll go into that at another time.
Heat of hydration is a little off topic but OKBlocker is right.
JDC
Edited by - jdcoombs on 01/07/2002 10:00:33 |
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