Determination of clay size fraction of marine clays

Abstract

This technical note describes a study on the effect of different dispersing agents and the quantity of same on the grain-size distribution and in particular the percentage of clay size. The results confirm that the existing practice of using 100 mL of standard dispersing agent, viz. sodium hexametaphosphate and sodium carbonate solution, is suitable for marine clays also. The clay size fraction in a marine soil exists in the form of flocs, and hence a dispersing agent is imperative in determining the percentage of clay size fraction. This paper shows that the clay size fraction can vary significantly (4 to 45%) for the marine clays depending upon the dispersing agent used. It also brings out the importance of the need for using an initially moist sample for grain-size analysis in the case of marine clays. Initial air/oven drying before testing induces irreversible aggregation.