ACI Concrete Cover to Reinforcing Bars 1

[ajk1]

Does anyone know which ACI Standard specifies the concrete cover required to reinforcing bars in structures exposed to corrosive and non-corrosive environments and for footing poured against soil? It is not in ACI 318.

 

[BAretired]

Three inch cover for footings poured against soil according to Canadian standards. I think it is the same in the USA and I would bet that it is in ACI 318 but I don't have a copy so cannot cite the article. How much research have you done?

What type of corrosive environment are you asking about?

BA

 

[JAE]

ajk1 - ACI 318, Chapter 7 specifies concrete cover - at least for footings against soil - same as what BAretired says for Canada - same as in the US - 3".

Not sure about corrosive environments.

 

[JennyNakamura]

"Corrosive" environments were not specifically addressed by the ACE 318 until the 2008 edition. You need to reference the ACI 318-08 Chapter 4 which defines requirements for "Concrete by Exposure Class." That will refer you to Section 7.7.6 "Corrosive Environments."

 

[ajk1]

Yes you are right. ACI does cover this. Thank you for pointing this out.

My follow up questions are as follows, and pertain mainly to CSA A23.1-2009, but I am interested how ACI 318 covers some of these items as well:

CSA A23.1 Table 17: For "Cast against and permanently exposed to earth", CSA requires that there be 75 mm (3") cover but ALSO requires (assuming no sulphate exposure) that the concrete be at least CSA exposure class F-2 (which has a maximum w/cm = 0.55 and minimum air content of 4% - 7% for 20 mm (3/4") nominal maximum size coarse aggregate) even though the footing may be in a heated building . ACI has the same cover requirement, but seemingly not any limit on w/cm.

Question: Until the year 2000 when this w/cm & air content requirement was introduced into CSA, it was standard practice to use 75 mm cover but not to impose any w/cm requirement, other than the strength required for structural design. Is anyone aware of any problems with that traditional practice (for about 100 years) that would have warranted the change to CSA in 2000? I am doubtful that engineers are conforming with this w/cm for footings in heated buildings.

CSA A23.1 Table 17, lists "Beams, girders, columns and piles" as requiring 30 mm cover. What is meant by piles? I would include drilled piers in the usual definition of piles. In this case, wouldn't the piles fall into the category of "cast against and permanently exposed to earth" (assuming the steel liner is withdrawn) which required 75 mm of cover? What cover does ACI require for rebar in piles?

Footing Cast Against Skim Slab: if the footing is cast on a 75 mm thick skim slab (or sometimes called a mud slab), what cover is required for the bottom rebar? There is no categroty in CSA Table 17 to cover this case.

CSA & ACI; For basement walls cast against wood lagging (or against vertical drainage board fastened to wood lagging) what is the required cover? by ACI? by CSA?

CSA & ACI: does "earth" include "rock"?

 

[ajk1]

Sory, I just realized I had misinterpretted CSA, so here are my questions re-stated. Please disregrad my earlier post.

My questions are as follows, and pertain mainly to CSA A23.1-2009, but I am interested how ACI 318 covers some of these items as well:

CSA A23.1 Table 17: For "Cast against and permanently exposed to earth", CSA does not permit Class N concrete to be used for "cast against and permanently exposed to earth". Prior to year 2000, it seeminglly did. Is anyone aware of any problems with that traditional practice (for about 100 years) that would have warranted the change to CSA in 2000?


What is meant by piles? I would include drilled piers in the usual definition of piles. In this case, wouldn't the piles fall into the category of "cast against and permanently exposed to earth" (assuming the steel liner is withdrawn) which requires 75 mm of cover? What cover does ACI require for rebar in piles?

Footing Cast Against Skim Slab: if the footing is cast on a 75 mm thick skim slab (or sometimes called a mud slab), what cover is required for the bottom rebar? There is no categroty in CSA Table 17 to cover this case.

CSA & ACI; For basement walls cast against wood lagging (or against vertical drainage board fastened to wood lagging) what is the required cover? by ACI? by CSA?CSA & ACI: does "earth" include "rock"?

 

[BAretired]

See the following opininion.

http://www.icjonline.com/views/POV_VRK.pdf

Drilled piles have always had 3" cover in my location. I don't think it is practical to reduce that very much as it will be too difficult to place the reinforcement cage without dislodging soil.

A footing on a skim slab does not require special cover as it is already protected by the skim slab. One inch cover would seem reasonable.

Does soil include rock? Don't know...we don't have any rock in my area. Conservatively, I guess it does.

BA

 

[ajk1]

To BARetired - thanks. I would be reluctant to reduce the cover to one inch for footings on skim slabs because moisture can seep into the joint between the skim slab and the footing. My suggestion is 2".