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Re: Embeded reinforcing steel in soil?

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Ken,
 
The reinforcing steel embedded in soil will have a very limited serviceability period.  That period may be longer in some soils than in others, but I would not expect a serviceability period in excess of a very few years in any case.  Steel embedded in concrete, which has a high protective pH, begins to corrode when the pH around the steel drops below a certain pH that is on the alkali side of [and well above] 7.  The alkalinity drops as atmospheric CO2 slowly penetrates and reacts with the compounds that produce the alkalinity [it's called carbonation].  Reinforced concrete that is more than 50 years old probably has some rebar corrosion underway as you read this -- reinforced concrete that is 100 years old is likely to have corrosion damage.  If the soil you are dealing with is not highly alkaline, you can expect corrosion to begin immediately.  If the soil surface is exposed to weather, moisture penetration from rainwater will probably start the delivery of CO2 to the vicinity of the steel in the first wet season.
 
Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net