Abstract
Soil particle less than 75 microns can be analyzed for the distribution of various grains sizes of silt and clay. This is achieved through hydrometer test. In this study the effect of different dispersing agents on the hydrometer test were studied. Four different solutions of dispersing agent and soil samples were prepared. The first solution was prepared using 35 g of sodium hexa metaphosphate with 7 g of sodium carbonate (solution I). Second solution is prepared using only 40 g of sodium hexa metaphosphate per 1 litre of solution (solution II). Third solution is prepared using 40 g of sodium carbonate (solution III) and the fourth is prepared without using any dispersing agent rather, the two soil samples used were dissolved in distilled water (solution IV). After comparative analysis, solutions I and II were recommended as the best method for preparation of soil solution for hydrometer test. Percentage passing obtained for solution I differs from solutions II, III, IV by 3.20, 6.88 and 24.07 respectively; for sample A and 3.22, 11.1 and 19.52 respectively; for sample B. Solution I and II are consistent for both samples whereas solution III is not consistent showing that it depends on the nature of soil being dispersed. Therefore, sodium carbonate is added to solution I to reduce its hardness. The results obtained showed that solution I and II are recommended only as prescribed by BS and ASTM respectively.
Highlights
The common laboratory method used to determine size distribution of fine-grained soil is called hydrometer test
In hydrometer test a small amount of soil is mixed into a suspension and its settlement is observed over time
Whereas ASTM standard method of particle size analysis D422-ASTM [2] suggest that 125 ml of solution of sodium hexa metaphosphate shall be used in distilled water at the rate of 40g of sodium hexa metaphosphate per litre of solution [1,3]
Summary
The common laboratory method used to determine size distribution of fine-grained soil is called hydrometer test. In hydrometer test a small amount of soil is mixed into a suspension and its settlement is observed over time. A hydrometer test is conducted by taking a small quantity of a dry and fine grained soil and thoroughly mixing it with distilled water to form a paste. Whereas ASTM standard method of particle size analysis D422-ASTM [2] suggest that 125 ml of solution of sodium hexa metaphosphate shall be used in distilled water at the rate of 40g of sodium hexa metaphosphate per litre of solution [1,3]. The hydrometer is read, the diameter D (cm) of the particle at time t (second) is calculated from Stoke’s law as. Stoke’s Law can be expressed in terms of unit weight of soil as follows. This work studied the comparative effect of different dispersing agents on hydrometer test result
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