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Marblehead (Marine/Ocean) (OP)
7 Sep 11 12:59
Hello:

We are installing a steel breakwall for a marina in fresh water Lake Erie. I know that the backfill cannot be dirt as dirt holds water and will produce great pressure against the steel wall.

We want to backfill with stone so that water will flow through the stone and drain out weep holes in the steel wall reducing pressure against the wall. My question is, if we use limestone for backfill will it rust the steel wall. I so, what stone should we use for backfill so that the wall will last longer?

Thank You.

 
MiketheEngineer (Structural)
7 Sep 11 13:22
Not too sure about the limestone - but think not a problem.  But don't forget even with rock the back fill will/could completely fill with water - at least until it drains out.
Chance17 (Chemical)
9 Sep 11 13:32
It seems to me that water plus steel will always produce rust
regardless of the fill material.
SJones (Petroleum)
10 Sep 11 15:50
If it gets wet, you will still need cathodic protection.  So, just ensure that you don't shield the CP.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04
 

rconner (Civil/Environmental)
12 Sep 11 23:47
I think it is generally considered that crushed limestone backfill, that has a tendency to result in high pH for some time in an aqueous environment, is generally considered a material non-corrosive to steel. However, it is of course also a quite porous backfill that may eventually allow infiltration of more corrosive fine soils etc. into same, if same are in the area, and/or it can be inadvertently mixed with clods of more corrosive material, from jobsites in the backfilling operation. If absolute corrosion protection is warranted, and presented with such risks, barriers and/or other more dependable corrosion protection means are required as others have indicated. For more information see e.g. reference at http://books.google.com/books?id=wCfu4WDn8J4C&pg=PA6&lpg=PA6&dq=U.S.+Steel+high+pH+limestone+backfill&source=bl&ots=QjSsxNaewF&sig=MPou4g4j_O1nphgivCqCjN_rTG8&hl=en#v=onepage&q=U.S.%20Steel%20high%20pH%20limestone%20backfill&f=false , as well third FAQ at   http://www.dipra.org/faq/corrosion.cfm etc. It should probably also be cautioned that high pH environments can actually be corrosive to some other types of metal and materials (other than ferrous).

 

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