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Re: Steel Fibers Replacing Structural Reinforcing?

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Jonathan,
 
Would long-term serviceability of the concrete be impeded by the steel fibers?  How is the expansive effect of corrosion of the steel fibers addressed?  Why should one not expect that steel fiber-reinforced concrete would be subject to early-onset, progressive weakening of the structure? 
 
Conventionally reinforced concrete provides protective concrete over steel reinforcing cover that delays the damaging effects of carbonation and resultant rebar corrosion.  Steel fibers incorporated into the mix will result in steel in contact with, or very close to the surface -- corrosion will probably begin very soon after the construction is completed.  As steel corrodes, the resultant rust occupies much greater volume than the steel that produces it; the internal pressure of the expanding rust causes cracking and spalling -- will this not damage the foundation?
 
A little rust from a rebar has insignificant effect on the cross section of the bar.  The same amount of rust from a fiber may represent a significant portion of the original cross section of the fiber, and a significant weakening of the reinforcement.
 
Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net