46 A clean dry density bottle was weighed and recorded as M1. The density bottle was filled with water and the volume of water measured using a measuring cylinder and recorded as V. The density bottle was emptied and dried in an oven. The density bottle was refilled with the particles shaking the bottle and weight recorded as M2.
Calculate:
Mass (M) = M2 – M1 Density (D) = Mass (M) Volume (V)
3.11.4 Method for calculating soil porosity:
Soil porosity is calculated from the relationship below:
Soil Porosity = { 1 – bulk density } x 100 { Particle density }
47 four times.
3.12.4 Dispersion and shaking:
1. 200ml of deionised water and 20ml of 25% sodium hexametaphosphate was added.
2. The bottle was placed on an end-over-shaker and shook for 16hours (overnight) at 15rpm 3.12.5 Procedure:
1. On completion of shaking, the prepared sample and dispersed samples were transfered to 1 L measuring cylinders and filled to the 1 L mark with deionised water and the hydrometer used was noted.
2. The sample was stirred with a plunger for 20-30 seconds ensuring that all materials at the bottom are brought into suspension. At the end of stirring, the plunger was removed and the interval timer was started immediately.
3. After 4 minutes of sedimentation, the hydrometer was immersed to a depth slightly below its floating position and allowed to float freely. A reading was taken at 5 minutes at the top of the meniscus and recorded to the nearest 0.5g/L.
4. The hydrometer was removed slowly, rinsed clean and placed in a sedimentation cylinder filled with deionised water and 20ml of 25% sodium hexametaphosphate (blank solution).
The water temperature in the blank cylinder was the same as that of the soil suspension.
5. The hydrometer was re-inserted in the soil suspension for reading at different periods taken in the same manner as above. At about the same time as each soil suspension hydrometer reading, a hydrometer and temperature reading was taken (to the nearest 0.5oC) of the blank solution. The hydrometer was read at the top of the meniscus. The hydrometer was left in the blank solution between readings.
Calculation:
Calculate for each hydrometer reading the summation percentage (P) P(%) = (H) x 100
W
Where :
48 H = Hydrometer reading in soil suspension(g/L)
3.12.5 Sand measurement:
1. The contents of the cylinder was passed through the 0.70mm sieve and thorough washed free of all fine particles. Those particles retained on the sieve are the coarse sand fraction.
2. The coarse sand was transfered from the sieve into a pre-weighed, numbered weighing tin. It was allowed to dry by placing in a drying oven between 105oC and 110oC and cooled in a dessicator afterwards and then weighed.
After the sedimentation period, the suspend clay fraction was decanted from the settled silt particles and discarded . The settled silt fraction was then dried in the beaker at 1050C to a constant weight. The soil sand % and silt % were calculated based on their fraction of the original sample mass:
% Sand = ( oven dry sand mass) X 100%
Original sample mass
% Silt = (oven dry silt mass) X 100%
Original sample mass
The % clay was determined by calculating the difference of 100 % minus the sum of the % sand and % silt,
% Clay = 100 – ( % sand + % silt)
3.13 PROCEDURE FOR DETERMINING PERCENTAGE LOSS ON IGNITION OF INORGANIC SOILS:
3.13.1 Scope
This procedure is intended as an indicator of the amount of coarse (+ 75µm sieve) mica present in inorganic soil such as the residual soils of the SC piedmont (South Carolina census designated place in US). The water of crystallization contained within the mica is driven off by ignition at approximately 10000C. The loss in mass of the sample is an index to the amount of mica present.
3.13.2 Apparatus:
• High temperature porcelain crucibles
• Muffle furnance capable of maintaining a temperature of 10000C ± 500C
• Desicator
49
• AASHTO Class B Analytical Balance 3.13.3 Test specimens:
This test is normally performed in conjuction with particle size analysis (SC T 34 or AASHTO T 88 ). The sample is prepared by recombining and mixing thoroughly the material above the 75-µm sieve from the sieve analysis performed on the portion of the sample passing the 2-mm sieve.
3.13.4 Procedure
The soil sample was reduced in size to approximately 20 grams by quartering using a riffle splitter. Visual inspection confirmed no large mica was present after quartering.
The crucible was cleaned, weighed and recorded to the nearest 0.01 gram.
The sample was placed in the crucible and the weight of the sample and crucible determined to the nearest 0.01 gram.
The temperature of the oven reached 10000C (± 500C) before placing the crucible in it.
The sample was allowed to remain in the oven at 10000C (± 500C) for 45 minutes.
The crucible was removed from the oven and placed in the dessicator to cool until it reaches room temperature before it was weighed again.
The crucible and sample was weighed and recorded to the nearest 0.01 gram.
Calculate the loss on ignition as:
Loss (L) = mass (grams) of crucible and sample prior to ignition − mass of crucible and sample after ignition
Calculate the % ignition loss for the material passing the 2-mm sieve as:
% Ig = (P x L)/ M X 100 Where:
P = percentage of material above the 75-µm sieve. This corresponds to the percentage of total sand in the material passing the 2-mm sieve on the soil test report.
L = loss on ignition (grams).
M = mass of sample prior to ignition. This procedure calculates the % ignition loss as a percentage of the material passing the 2-mm sieve. If the % ignition loss of the sample as a whole is desired, multiply the value for % ignition loss calculated in the
50 last step (before calculation of loss on ignition) by the percentage of material passing the 2-mm sieve in the sample as a whole.
Calculations
The loss on ignition is calculated as follows:
Wt. of sample = w1 Wt. of crucible = w2
Wt. of crucible and sample after ignition = w3
Wt . of crucible and sample prior to ignition = 195.33 grams
Weight of dish after ignition – Weight of sample before ignition X 100 Weight of sample