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RE: concrete in corrosive environment

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Your biggest problem is the hydrogen sulfide, but how bad it is depends on the concentration.  In waste water treatment plants, a barrier on concrete is required like T-Lock, select spray applied polyurethane coatings, or coal tar epoxy coatings.  Hydrogen sulfides will corrode steel and degrade the concrete directly.  As opposed to chlorides which penetrate and passivate the concrete and corrode the reinforcing steel.

Generally hydrogen sulfides are only a problem above the water line where they actually form sulfuric acid.  If you do in fact have dissolved hydrogen sulfides without exposure to air, only marginal protection (good dense concrete) is required.  

Don't try galvanizing.  Sulfuric acid will really go after zinc.

Silica fume admixtures have shown a certain degree of effectiveness in hydrogen sulfide exposures.

If you have a very aggressive corrosion exposure.  You could drill auger cast piles and place H or pipe piles in them with a coal tar epoxy protective coating.  T-Lock could be used to line the perimeter of the pile cap.  It is expensive.  T-Lock is about $10 per S.F.  These types of foundations have been used.

For further information, the corrosion folks have a group called NACE (National Association of Corrosion Engineers).  They have a web site http://www.nace.org/nacehome.html.

Regards,
Harold Sprague, PE
Krawinkler, Luth & Assoc.
4412 W. Eisenhower
Loveland, CO 80537
970-667-2426 voice
970-667-2493 fax
hsprague(--nospam--at)klaalov.com

-----Original Message-----
From:	Jerry King [SMTP:KINGJW(--nospam--at)sverdrup.com]
Sent:	Wednesday, June 17, 1998 1:52 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	RE: concrete in corrosive environment

I am involved in a project in Newark NJ where a building is being designed, supported on piles.  A environmental investigation was performed at the site.  The results were that for the soil, methane and hydrogen sulfide were found in the soil gas sample.  The report states that hydrogen sulfide is corrosive to metal and cement.

In the groundwater samples, the Total Dissolved Solids indicate that brackish conditions exist (> 1000 mg/l), the chloride concentrations are considerably above the average of 6 mg/l, and hardness values indicate relatively hard groundwater (>200 mg/l), and concentrations of sodium ranged from 10-100 mg/l to > 100 mg/l, with the higher concentrations deeper within the saturated zone ( at least 20 feet below grade).

My problem is that I am now trying to determine whether steel or concrete piles would be better in these conditons, and what to specify for the concrete in the pile caps and grade slabs.  When I called the environmental engineer, he was unable to offer any advice.

Any help anyone could give would be greatly appreciated.

Jerry King, PE

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