Effect of hydrometer type on particle size distribution of fine grained soil

Abstract: The particle size distribution of soils, including clay content is of utmost importance in the field of Geotechnical Engineering. The hydrometer analysis is the most widely used technique for analyzing the particle size distribution of the fine grained fraction of soil. The various hydrometer test methods (internationally) generally vary mainly in the use of the prescribed dispersing agent. In addition, certain methods vary with the use of the prescribed hydrometer. The purpose of this study was to establish the optimum concentration and volume of the three dispersing agents (calgon, sodium pyrophosphate decahydrate and sodium tetra pyrophosphate) using the ASTM Hydrometer 152H: E100 (instead of the Bouyoucos hydrometer 152H) for three soil classes, selected for their varying activity. The results indicated that the ASTM hydrometer 152H: E100 generally yielded lower results than hydrometer 152H in terms of percentage fines, with the differences varying from 38% to -65% for all the soils and the dispersing agents