Clay Minerology

[SirAl]

I am based in an area where surfacial soils (< 5m to 6m) are predominately lacustrine clay deposits. The upper portion (1.5m - 2.0m) are high plastic clays with liquid limit and plastic limit values commonly in the 60% to 85% and 23% to 33% ranges respectively. This upper layer grades to a silty clay with liquid limit and plastic limit values in the low to mid 50% range and high teen to low 20% range respectively. Natural moisture is often dry of optimum and swell displacements are a major issue with concrete flatwork in this region. I am interested in learning more about the minerology of the clays (i.e. %illites, montmorilonites, kaolinites). Are there general correlations based upon Atterberg limit index values? What other types of testing can be done to obtain this information? Where can this testing be conducted?

 

[Focht3]

Good questions!

Are there general correlations based upon Atterberg limit index values?

No. You get general trends, but not specific mineralogy of the soils.

What other types of testing can be done to obtain this information?

X-ray diffraction - and interpretation of the results - is the only &quot;sure&quot; way. At least, to my knowledge.

Where can this testing be conducted?

It depends on where you are located - contact the nearest university with a good geotechnical engineering program for help. Or post your location on this forum and see if anyone has a suggestion.

 

[dirtsqueezer]

SirAl,

Howdy. I'm not sure where you're located, but in Washington State, there are soil surveys that are publicly available. I think they'll even ship them to you free of charge. Otherwise, I'd also suggest you find a local geologist and take him out for drinks. If not that, then at a geology club meeting or at the university. There's got to be someone who knows the ins and outs of expansive clay in your neighborhood. By the way, what's the locality? Now you've got me interested.

 

[SirAl]

Thankyou, Focht3 and dirtsqueezer, for taking the time to respond. I am located in northwestern Alberta. The clay minerology question certainly is in the realm of geology as you suggest. The Alberta Geological Survey would seem to be a reasonable starting point.