AS 1289.3.6.3:2020 pdf free download – Methods of testing soils forengineering purposes Part 3.6.3:Soil classification tests-Determination of the particle sizedistribution of a soil- Standard methodof fine analysis using a hydrometer

AS 1289.3.6.3:2020 pdf free download – Methods of testing soils forengineering purposes Part 3.6.3:Soil classification tests-Determination of the particle sizedistribution of a soil- Standard methodof fine analysis using a hydrometer.
— 4 Reagents
Only reagents of recognized analytical grade and distilled water or water of equivalent purity shall be used:
(a) Stock dispersing solut Eon — shall be prepared as follows:
(I) Dissolve 33 g of sodium hexametaphosphate together with either 7 g olanhydrous sodium carbonate (Na2CO3) or 18.9gof hydrated sodium carbonate (Na2CO3JOH2O) in distilled water to make I L of solution.
The decahydrate (Na2CO3.10I120) is more readily soluble in water than Is anhydrous sodium carbonate (NazCOj) which is only sparingly soluble. The use of warm distilled water will also accelerate the solution of the chemicals.
(ii) Store the stock solution in a dark bottle away from sunlight. The date of preparation, or expiry date, shall be recorded on the bottle. The stock solution will be unstable and shall not be used if more than one month old.
NOTE Sodium hexamet.iphnsphate is recommended as the dispersing agent as It has been found suitable for a wide range of soils. However. lateritk soils cannot be dispersed adequately with sodium hexametaphosphate and the use of sodium phosphate is advised (Wintermyerl 1))
(b) Barium chloride solution — shall be prepared by dissolving 50 g of barium chloride in 1 L of distilled water.
5 Apparatus
The toliowing apparatus shall be used:
(a) An hydrometer conforming to ASTM E 100 and with the following features (see Figure 1):
(I) The glass used for the bulb and stem Is as free as possible from visible defects.
(ii) The stem and bulb are circular in cross-section and symmetrical about the longitudinal axis, with no abrupt changes in cross-section, which may trap air bubbles or hinder cleaning or drying.
(III) The basis of the scale is either density in grams per milllhtre (gJmL at 20 °C or grams per litre (g/L of colloid in suspension at 20 C. The g/mt. scale is normally calibrated from 0.995 to 1.038 with graduation lines at every 0.0005 g/ml. and a maximum permissible scale error of plus or minus one scale division (0.0005 g/mL.).
7.4 Preparation for sedimentation
The procedure shall be as follows:
(a) Transfer the liquid to the stirring device cup and operate for 15 mm. If the volume of liquid exceeds the capacity of the cup, this process will need to be completed in multiple steps as follows:
(i) Transfer the mixture to the high-speed mechanical stirrer or to the air-jet dispersion cup, usmgajet of distilled water.
(ii) Transfer the suspension that has passed through the sieve to the 1 L measuring cylinder and make up to exactly 1 L with distilled water. This makes the suspension to be used in the sedimentation analysis.
(b) For soils likely to surfer severe structural breakdown, It Is recommended that the air dispersion device be used, and mechanical dispersion not be used before washing over the 75 pm sieve.
(c) In the case of (a) or (b) operate the dispersion device for 15 mm. When using the mechanical stirrer use the baffle in the mechanical stirrer container. When using the air-pet dispersion device, operate It at a gauge pressure of 140 kPa ± 10 kPa.
7,5 Sedimentation
The procedure shall be as follows:
(a) Place the I L cylinder containing the suspension in the constant temperature room, or bath and preferably leave It to stand until It has attained the ambient temperature of 20 °C ± 1 °C. Close the mouth of the cylinder with the palm of the hand, or with a suitable watertight stopper or lid, and turn the cylinder end over end thoroughly for about 60 rotations in I mm.
(b) Immediately after shaking, place the cylinder on a firm, level and vibration-free place In the constant temperature room or bath. Then proceed as follows:
(I) Start the stop-clock and record the time of commencement of the test.
(II) Immediately Immerse the hydrometer to a depth slightly below Its floating position and allow it to float freely.
(III) Take readings at the top of the meniscus at 0.5.. 1. 2., and 4-mm Intervals and record readings to the nearest gram per litre (or 0.000S g/mL (Rh).
(lv) Remove the hydrometer slowly, rinse it In distilled water, and place it In another cylinderof distilled water, which is at the same temperature as that of the suspension.
(v) Re-insert the hydrometer In the suspension and take readings at elapsed times of 8, l5and30minand 1,2,4andllhrs.
(vi) Remove the hydrometer after each reading, rinse It. and replace It In the cylinder of distilled water.
(vii) After the 4 h reading take further readings once or twice daily up to 48 h after dispersion, recording the times of reading. (Always insert and withdraw the hydrometer carefully when taking a reading to avoid undue disturbance of the suspension, allowing 10 s for each operation. Avoid vibration of the sample from any source.)
(c) Record the temperature of the suspension once during the fIrst 15 mm of sedimentation and then after every subsequent reading. Record the temperature, accurate to within ±0.5 °C (see C1aueI Note 7).