AS 1141.19:2018 pdf free.Methods for sampling and testing aggregates Method 19: Fine particle size distribution in road materials by sieving and decantation.
NOTE 1 Complete dispersion in the initial pours is not essential, provided that continual dilution with ammonia is carried out. The addition of ammonia and stirring will in most cases complete dispersion eventually. With heavy clays, the first two pours should be delayed because the settling of some of the coarser particles may be retarded by an excess of finer material. Typically a minimum of 10 mm should be sufficient (see Table 1).
NOTE 2 If the standard ammonia solution fails to disperse the soil particles, other agents may be used. Two of the more common dispersing agents are as follows:
(a) Sodium oxalate — Add 1 g of sodium oxalate to the soil and water prior to boiling. Use water only to refill beakers after each decantation.
(b) Sodium hexametaphosphate — Make a stock solution of 62 g of sodium hexametaphosphate in 1 L of water. Add 5 mL of this stock solution to the soil and water prior to boiling. Add 5 mL of the stock solution to each beaker after each decantation and refill with water. This dispersing agent is effective with many lateritic soils.
NOTE 3 Even though the liquid poured off may be clear, it is still possible that dispersion is incomplete.
Incomplete dispersion is shown by —
(a) a thin layer of flocculus in suspensions overlying the sand and silt; or
(b) the residue in the beaker after drying being “cemented”, or having a “cemented” surface layer. This occurs in some sandy materials when active clays are present. In such cases a stronger dispersing agent than ammonia should be tried.
(j) Carefully pour off liquid until the quantity remaining corresponds to the lowest mark on the beaker (30 mm from the base). It is essential that the pouring shall not create turbulence.
NOTE To facilitate decantation without causing turbulence, the beakers should be precalibrated to relate the angle of tilt to the amount of water required to coincide with the lower level mark. For the beakers commonly used, the angle of tilt is about 45 degrees.
(k) Repeat Steps (f) to (j) until the liquid poured off is clear. If the liquid poured off is not clear after 16 pours, the test shall be discontinued and repeated with an alternative dispersion agent and new sample, or reported as incomplete dispersion.
(1) After the final pour, stand the beaker at an angle of 45 degrees for not less than 5 mm and pour off the balance of the clear water, taking care not to remove any of the remaining particles of material.
AS 1141.19 pdf download.