LAUSR

The standard plastic limit test, based on Atterberg’s original manual thread rolling method, is a simple, quick, and inexpensive procedure that has received very little attention for improvement since its initial inception over a century ago even though it receives much criticism because of its poor reproducibility. An investigation into the shortcomings of the standard test by means of manual rolling path tests examines the relationships between the water content, diameter and condition of soil threads, and the distinct ductile–brittle transition that occurs at the plastic limit. The ASTM and International Standards are compared, highlighting significant differences in their procedures. Modifications of the standard method are recommended to provide coherent objectives for a consistent rolling procedure, compatible considerations of diameter, and a more precise and authentic assessment of the end criterion at the plastic limit.