pyritic soils

[dmaxey]

We have been requested to determine if pyritic soils are present on a site. Is there an ASTM nethod for determining the presence of pyritic soils and when they are problematic?

 

[dik]

Pyritic soils are those with a high concentration of Iron Sulphide and breaks down to produce an acidic and sulphate rich material that can cause problems with concrete. In aggregates (I understand, but am not sure) it expands and can cause 'pop-outs' on the surface. It can also promote 'rust' staining of the surface.

Dik

 

[fattdad]

Pyrite (FeS2) oxidizes to iron oxide (FeOx) and sulfuric acid. It's very difficult to establish vegetation on such soils. That can make a problem releasing your E&S Bond. Not to say there can't be a concrete issue too, but you can design for that.

Is this project in Virginia?

Even if it isn't consider calling Lee Daniels, Virginia Tech. They have a lab that can run a test for sulfur equivalancy of some sort. Don't know those details. It's not too expensive either.

f-d

¡papá gordo ain’t no madre flaca!

 

[dik]

Fatdad... E&S Bond?

Dik

 

[fattdad]

usually contractors have to make sure the ground is revegated before the local jurisdiction will release their "erosion and sedimentation" bond, which is bond money that they'd otherwise use to finish the job.

f-d

¡papá gordo ain’t no madre flaca!

 

[dik]

Thanks... Never heard the term... Dik

 

[molerat2210]

I believe the pyritic soil are also refered to as Acid Sulfate Soils. These soils are well understood in tropical coastal areas. See papers from Austrailia and South Africa on how to identify. This is an emerging topic of discussion for temperate regions since these soils have recently been discovered to be more common the previously thought. We have also be tasked to address the issue in future geo reports by our local water and sewer commission here in MD. It may occur in some local formations and have low ph (<3.5) and expansion potential.

 

[dmaxey]

Thanks for the input. The project is in the Metro Atlanta, Georgia area where we have not seen as issue with pyritic soils. I assume that it was associated with an RFP from an area such as Virginia where it has been a concern.

Thanks!

 

[fattdad]

You may find this interesting:

http://scholar.lib.vt.edu/theses/available/etd-05212003-173107/unrestricted/ThesisAll.pdf

f-d

¡papá gordo ain’t no madre flaca!

 

[fattdad]

another link:

http://scholar.lib.vt.edu/theses/available/etd-10042001-123731/unrestricted/dissertation.pdf

f-d

¡papá gordo ain’t no madre flaca!

 

[WillisV]

Generally the major concern with pyritic soils is with the heave that can result during oxydation if pyritic sulfer content exceeds about 0.3 percent. Generally an issue in coal mining areas (Virignia, West Virginia). Not a concern in Georgia.

 

[dik]

Thanks WillisV. My concern is from a structural view... looks like there are other problems... didn't realise it swelled on oxidation... but, makes sense because it can cause 'pop outs'...

Dik