Reappraisal of the ASTM/AASHTO Standard Rolling Device Method for Plastic Limit Determination of Fine-Grained Soils

Given its apparent limitations, various attempts have been made to develop alternative testing approaches the standardized rolling-thread plastic limit (PLRT) method (for fine-grained soils), targeting higher degrees of repeatability and reproducibility. Among these, device-rolling techniques, including described in ASTM D4318/AASHTO T90 standards, based on original work by Bobrowski Griekspoor (BG) which follows same basic principles as standard thread-rolling (by hand) test, highly underrated some researchers. To better understand true potentials and/or limitations BG for soil plasticity determination (i.e., PLBG), this paper presents a critical reappraisal PLRT–PLBG relationship using comprehensive statistical analysis performed large diverse database 60 test pairs. It is demonstrated that given soil, RT methods produce essentially similar PL values. The 95% lower upper (water content) agreement limits between PLBG PLRT were, respectively, obtained ?5.03% +4.51%, both deemed “statistically insignificant” when compared inductively-defined reference ±8% highest possible difference repeatability, reported literature). Furthermore, likelihoods underestimating overestimating were 50% 40%, respectively; debunking notion presented researchers generally tends greatly underestimate PLRT. also shown degree underestimation/overestimation does not systematically change with changes properties; suggesting differences are most likely random nature. Compared PLRT, likelihood achieving consistent classifications employing (along liquid limit) was be 98%, identified discrepancies being cases plot relatively close A-Line. As such, can used confidence classification purposes.