tonette,

AASHTO administers laboratory proficiency tests using supposedly the same material for each lab. I can only assume that they engineer the soil to be tested in order to assure a high degree of uniformity between all samples. Perhaps they would be able to help either supply or direct you to someone that can supply your soil. The website is for the AASHTO Materials Reference Laboratory program (www.amrl.net)

Good Luck!

Jeff

Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com

I might suggest that you consider obtaining fly ash from a coal fired power plant.  The pond ash and you can do a bit of screening to get "all" silt; but in the case we have here, only 10 to 15% of our fly ash if fine sand.  The only drawback is that there is a large difference in specific gravity of fly ash to soil.

Does it need to be uniformly non-plastic silt?  Maybe you can use sieves to do it.  The only challenge would be separating out the plastic and clay particles from the non-plastic.